News aggregator

‘Are You Using This Idea for Your Thesis Research?’ [UPDATE]

The Broadleaf Papers - Thu, 02/28/2013 - 20:53

By Daniel D. Douglas

Are you using this idea for your thesis research?”

I heard this as I stood in front of a classroom full of old-growth forest ecology students. The question had come from Neil Pederson, who was sitting directly in front of me. He was asking this question because I had just spent the past 12 minutes discussing the intricacies of land snail biology and ecology that would make them great organisms to use for ecological modeling in regards to disturbance. Things such as their lack of mobility, susceptibility to desiccation and sudden change that would occur because of major disturbance make their preferences for habitat similar to the defining characteristics of old-growth. Neil looked at me with the excitement of a small child on Christmas morning because he knew that I could potentially be on to something.

So, you can imagine his dismay when I answered his question with “No, I hadn’t really given it any thought.” I know I winced (at least on the inside, if not physically) after I answered because I had suddenly realized that I could be passing up a golden opportunity. I remember walking back to my apartment that night, thinking about what had just happened. I thought about it another hour or so after I arrived home and then emailed Neil to discuss the potential that my presentation had for being used as a master’s research project. Long story short, we developed a research plan of attack with the help of David Brown, my co-advisor, to study how anthropogenic disturbance* can shape land snail communities.

Microsnails on the Honest Abe – can you find the 28 microsnails? Image: D. Douglas

Not many people study land snail ecology. I had the fortune of working under someone that did, Ron Caldwell, while I was an undergraduate at Lincoln Memorial University. I had become deeply interested in these ignored and overlooked organisms. So, as I entered graduate school in biological sciences at Eastern Kentucky University, I had a fairly strong background in “snailology”, aka malacology. I had been unsuccessful in finding a graduate program where I could continue to work with land snails and was wandering the halls of EKU uncertain about what I was going to do for a graduate research project.

What happened in Neil’s class that semester was really fate telling me this is what I should be doing. A year and a half later, I found myself sitting on my back porch sifting through leaf litter samples, picking out micro-snails, excitedly thinking “I’ve got something here.” It was clear that these organisms could be indicators of past human disturbance.

This research took me to some of the most memorable places that I’ve ever been. Since the availability of old-growth in Kentucky is sparse, my sampling sites were limited. The first place I sampled, Floracliff Nature Sanctuary, was just a few miles north in the Bluegrass Region of Kentucky and, oddly enough, a few miles outside of Lexington. It’s crazy to think that a place with trees hundreds of years old exists right outside a fairly large municipal area, but it does.

The EpiCenter, a relatively dense cluster of 300-400 year old chinkapin oak, in Floracliff Nature Sanctuary. Photo: B. James

Floracliff rests on the Kentucky River Palisades in a very rugged, deeply dissected network of gorges cut by streams over eons of geologic time. It also has some of the most spectacular examples of old-growth trees you’ll find in Kentucky, including the oldest known tree in Kentucky to date: a 400+ year old Chinqaupin Oak.

Though this wasn’t true old-growth, it gave me some of the best results I got for the entire study: there was a clear separation of the land snail communities between old and young forest sites. In fact, abundance, richness, and species diversity, were all greater in the older sites. This is also the site where I found the most new county records (i.e. never documented from that county). These results only whet my appetite for more data from different forests.

The next stop was EKU Natural Areas‘ Lilley Cornett Woods Appalachian Ecological Research Station, a small patch of prime mesophytic old-growth forest in Letcher County. It’s bizarre to think that forests like this exists in the Cumberland Plateau portion of Kentucky, due to the fact that our countries insatiable thirst for natural resources has left the region in one kind of an ecological ruin. I was deeply impressed by this forest as wandered around. The snails at LCW did not disappoint either. I saw the same patterns as in Floracliff: old-growth forest had greater abundance, richness, and diversity. The highest species richness for the entire study came from LCW as well, which is something that I did not expect. The evidence was beginning to stack up.

Big Everidge Hollow, old-growth forest goodness, in in Lilley Cornett Woods. Photo: D. Douglas

My final study site was Blanton Forest State Nature Preserve. This preserve is over 1200 hectares and contains the largest tract of old-growth forest in Kentucky. Dominated mostly by oak and hemlock, the forest is very rugged and it had more rhododendron than I care to remember.  Nevertheless, it is impressive. Comparing Blanton to a nearby young forest didn’t necessarily give me the same exact results, statistically speaking, but I still saw the same trend of higher abundance, richness, and diversity of microsnails in old-growth forest.

A phatt, old-growth white oak in Blanton Forest, Bob posing, Merril coring. Photo: N. Pederson

You may be asking, “What does this all mean” or, “Well, he found that there is better habitat for these organisms in undisturbed forests. That’s doesn’t really seem novel.” In reality, this is novel. Better, it is important.

First, I documented that a minimum of several decades, if not more than a century, is needed for land snail populations to recover to a point that resembles what their assemblages looked like before human disturbance. As an important part of forested ecosystems in terms of nutrient cycling, organic material decomposition, calcium sequestration, and food sources for many other animals, it is vital that we know things like this so that we can better manage our forests for everything that lives there, starting from the ground up. Second, all of you must know that everything in an ecosystem is interconnected and, once one thing is removed, it can have cascading effects throughout the ecosystem. Better management practices will help us maintain ecological integrity of forests. Third, my findings also indicate the need for locating and protecting remnants of old-growth forests. As I have shown, old forests, whether true old-growth or lightly logged by humans a century or more ago, are biodiversity hotspots and therefore deserve protection beyond their representation of how complex forests are at great ages. And finally, my findings also indicate that land snails have great potential for being used as indicators of old-growth. This is something that many scientists, especially citizen scientists, have been chasing after for decades.

For myself personally? This means that I have a lot more work to do. Despite the fact that there are people out there that study land snails, they remain poorly understood. I feel as if it is my job to bridge that gap in the knowledge. I also hope that what I have accomplished with this research will open the door for future studies on not just land snails, but other non-charismatic fauna. I also hope that my work enables people to look at more than just the trees in old-growth forests. The trees are wonderful, and we are lucky to still have them, but there is a lot going on underneath those trees that we don’t know much about.

 

* = the linked article is open access and free for downloading – download away!

[UPDATE]

Earthwise picked up this study for their radio series on our changing environment. Hear their piece on land snails and old-growth forests here.

_________

Daniel Douglas earned his master’s degree in biological science from Eastern Kentucky University in 2011 studying terrestrial snails, important, but less charismatic creatures.

Recovering ‘Sea Spiders’ and Heading Home

Earth's Tectonic Plates - Tue, 01/15/2013 - 17:42

Recovering an MT instrument.

Lamont graduate student Natalie Accardo reports from the Pacific.  Blog 4: Jan. 13, 2013

The NoMelt project is more than just a seismic experiment; it also has an important magnetotelluric (MT) component. MT instruments measure natural magnetic and electric fields on the seafloor, allowing scientists to estimate the electrical conductivity of the underlying rocks. Conductivity is highly sensitive to tiny amounts of water and molten rock within the upper mantle and thus can help distinguish whether the mantle is “wet” (and thus easy to deform) or “dry” (rigid and plate-like).

To obtain information concerning the conductivity of the mantle, six long-period MT instruments were deployed along with the seismographs from the R/V Langseth in 2011. These instruments, which appear more like sea spiders than scientific hardware, sit on the ocean floor and record electrical and magnetic fields approximately every minute. We recover these instruments in the same way that we retrieve the OBS (previous post), although they proved to be much more shy than the OBS in communicating with us. We welcomed back our first MT instrument on a dark and windy night, and over the course of two weeks we recovered five additional instruments without incident, displaying them in all of their neon-orange glory on the stern deck.

With the last instruments safely strapped down, we have put the NoMelt site in our rearview mirror and are steadily speeding to our final destination of Honolulu. Sunny skies and calm seas accompany the slowing pace of activity during our four-day transit to port.  Behind the boat, we trail fishing lines with every color of bait in the hopes that a tuna or mahi mahi might take a bite. Deck chairs have snuck their way out from the shelter of the hangers and onto the sun-drenched back deck where we, like moths to a lantern, try to soak up every last ray of sun before we must head back to the chilly Northeast.

Today we passed close enough to the island of Hawaii to give us our first glimpse of dry land in almost a month. The crew poured onto the main deck to snap photos and hunt for the tiniest glimpse of cellphone reception. There may be no better way to be welcomed back to land than the awesome sight of Mauna Loa towering above the clouds. Overall, the trip has been a great success. Most of our instruments survived their year of solitude on the dark, cold seafloor and came back to us with a set of unique and priceless data. We consider ourselves lucky to have gotten the chance to visit this remote region of the world, which will likely not see comparable human activity for some time.

Until next time, Aloha!

Santa Comes Bearing an OBS

Earth's Tectonic Plates - Thu, 01/10/2013 - 11:44

Lamont graduate student Natalie Accardo reports from the Pacific.  Blog 3:  Jan. 1, 2013.

Christmas found the R/V Melville in the middle of the Pacific Ocean on the last day of a seven-day transit to the NoMelt Project site. In a coincidence that we hoped would be auspicious, we reached our first OBS site late that night. As much as we yearn to be home to do celebrate the holidays with our families, we also realize how fortunate we are to have the chance to do what we do. Many of us began Christmas day with phone calls home to offer holiday greetings to our families and loved ones. Then the entire crew mustered on the upper deck for the requisite group photo, with more than one Santa Claus in attendance. Sunshine abounded as the captain led a crew-wide gift exchange that produced enough chocolate candies to feed an army. The rest of the day was filled with a “coits” (a ring toss) tournament on the main deck, where two young female scientists (that is us!!) came from behind to win the championship and all the pride and glory that come with it. An epic feast topped off with homemade pies and cakes ended the day for most of the crew; for the science party our adventure was just beginning.

We arrived at the first OBS station late into the night of the 25th with apprehension abounding. Recovering OBS instruments from the ocean floor is always a tricky business, especially in our case; these instruments have been sitting beneath more than 3.5 miles of water for over a year. With cold, tired batteries powering the instruments’ acoustic transponders, communicating with them through miles of ocean currents amounts to a whispered conversation on a stormy night.

We initiate communication with an OBS by transmitting audible “chirps” from a communications box in the main science lab to a transducer on the ship’s hull. The transducer acts as a speaker to transmit the chirp through the ocean and down to the instrument. If the OBS is alive and well, it transmits seven chirps in response. Given the distance these signals have to travel, it takes about eight long, stressful seconds to hear the instruments reply. Sometimes there is no reply, and we try again, at different locations, from different angles, with alternate acoustic devices.

Once we know an instrument is up and running, we conduct an acoustic survey by cruising around and sending continuous chirps. We measure the time it takes for the instrument to chirp back to determine the distance to the OBS, providing a precise estimate of the instrument’s actual location on the seafloor. Once we have completed the survey, we are ready to bring the OBS up. We send another series of commands that tells the instrument to release itself from the seafloor and then monitor the distance to it as it rises through ocean. Once on the surface, the captain skillfully steers the ship very close to the OBS so that we can hook lines onto it and pull it safely on board.

Our Christmas Night OBS was successfully recovered, and by New Year’s Day we had retrieved 12 OBS and one magnetotelluric instrument (to be discussed in the next installment). Sadly, two instruments never responded and are assumed lost to the deep; we are likely to never know why. Our success can be seen in the growing army of instruments that stand at attention on the main deck.

We are completing the charge around the perimeter of the deployment, picking up instruments approximately every 10 hours. Soon we will make the turn and head onto the central line of the deployment, where interstation spacing is much shorter and the recoveries come hard and fast. From the Pacific we wish everyone a happy and healthy New Year!

Transiting the Pacific

Earth's Tectonic Plates - Sun, 12/30/2012 - 18:18

Lamont graduate student Natalie Accardo reports from the NoMelt recovery cruise.

Blog 2:  Dec. 23, 2012

Calm seas and sunshine find the R/V Melville in the Pacific.

Today marks our sixth day aboard the R/V Melville on a journey to a remote region of the Pacific to retrieve seismic instruments that have been quietly recording earthquake signals on the ocean floor for the past year. We have covered more than 2,600 km thus far but must cruise for another two and a half days before we reach the NoMelt project site. We have been making good time — the ship’s crew has been pushing the Melville to move at a quick pace, 12.3 knots or 14 miles per hour – and should be at the project site around midnight on the 25th of December.

The Melville initially met rough seas off the coast of California that forced most of the science party to remain horizontal in our bunks in an attempt to sleep off the affects of seasickness. We hastily tied down laptops, keyboards, and a glittering Christmas-themed snow globe so that they would not be chucked about by the rolling waves. Sticky mats and cup holders found their way into the mess hall so that the those of us who could stomach a meal would not find ourselves with a lap full of spaghetti or coca-cola.

However, calm seas found their way to us two days out of port and have stuck with us since. Hotter temperatures and increasingly sunny days remind us that we are steadily cruising toward our tropical destination. We fill our days at a leisurely pace acquiring bathymetric and magnetic data from the ship’s onboard instruments, deploying drifter instruments, and working on projects we’ve brought from home. As we near the project site, the pace will pick up, and the science party will commence 24-hour round-the-clock scientific operations.

A “drifter” instrument floating away from the R/V Melville.

The science party makes up only six of the total 30 people on board. The rest represent the talented, permanent crew of the Melville, who work tirelessly to keep her safe and operational in the open ocean. Their vocations span the gamut from the engineers that keep the huge diesel engines humming smoothly to the computer technicians that keep the Internet running and the onboard ship computers (and scientists!) happy. The crew is gregarious and inviting, welcoming any question or concern, no matter how banal. They may even invite you to join in their card games … though few of us are brave enough to test their skills.

Christmas and New Year’s are just around the corner and promise to be exciting, as they will mark our first days retrieving the OBS from the deep. Until then we wish everyone safe holiday travels and happy holidays!

One Year Later – Return to the NoMelt Site

Earth's Tectonic Plates - Sun, 12/30/2012 - 18:03

The R/V Marcus G. Langseth completed the initial portion of the NoMelt experiment on Dec 29, 2011. In the subsequent year, scientists began analyzing the active-source seismic data collected on that cruise, constructing initial models of the oceanic plate. The full analysis awaits the so-called “passive source” data – the year-long recordings of earthquakes and natural electrical and magnetic signals on the instruments that remain on the seafloor.

On Dec. 18, 2012, the R/V Melville departed San Diego to recover remainder of the NoMelt instruments and data. The expedition includes two scientists from Columbia’s Lamont-Doherty Earth Observatory: Post-doctoral scientist Patty Lin and graduate student Natalie Accardo. Natalie is sending regular reports from the ship, and I will post them here.

Post 1:  Natalie Accardo, Dec. 19, 2012.

Map displaying the NoMelt project site located ~1200 km southeast of Hawaii.

In the early hours of Dec. 18, a team of scientists aboard R/V Melville set out from San Diego to a remote portion of the Pacific Ocean on a trip that will take 28 days and cover more than 8,500 kilometers. On this voyage, we aim to recover 27 ocean bottom seismographs (OBS) instruments that have been sitting silently on the ocean floor for nearly a year. Throughout their stay on the seafloor, the OBS have been continuously listening and recording the shaking caused by distant earthquakes all over the world. By recording ground motion, we can constrain seismic wave properties and in turn the geologic characteristics of the oceanic plate. With this information, we hope to answer the multilayered question of what defines a tectonic plate.

For decades, geologists have focused most of their attention on locations where tectonic plates come together (i.e. subduction zones like Japan) and break apart (i.e. rift settings like the East African Rift System). Yet to better understand the complex processes happening at those sites, we must first understand the fundamental characteristics of a tectonic plate. For further information concerning instrument deployment and other aspects of this project, please refer to previous blog entries.

It takes seven days to make the 4,300 km journey from San Diego to the NoMelt OBS sites. During the transit time, we use instruments aboard the Melville to map topography and gravity of the ocean floor. Additionally, at regular intervals we toss “drifter” instruments overboard. These so-call “instruments of opportunity” were designed by students at the University of California San Diego (UCSD) to be deployed by any research vessel traveling through an area of interest. They are completely autonomous and will record sea surface information (temperature, salinity, etc.) wherever the currents take them, data that will be of use to oceanographers at UCSD.

Today marks only our second day on board and has given us our first true glimpse of the open ocean. Rocky seas have confined most of the science party to their bunks in a group effort to retain what is left of our last meal. However, the promise of calmer weather in the coming days has brought some cheer to the entire crew.

Role-Reversal (and Some Fun) at AGU

American Geophysical Union Fall Meeting - Tue, 12/18/2012 - 10:31

Francesco Fiondella is normally behind the scenes writing web stories, developing audio slideshows and videos for the International Research Institute for Climate and Society (IRI). But at this year’s annual American Geophysical Union (AGU), the tables were turned for a brief moment. He was video ambushed by climate scientist Andrew Robertson and forced to explain a poster he made with me and fellow IRI’er Brian Kahn about unconventional ways scientists can communicate with the public online. The poster covers our experiences with an “Ask Me Anything” session on the popular social news site, Reddit.com; creating a Storify to curate the online conversations that took place during our recent State of the Planet conference on Twitter and Facebook; and using Projeqt to create a visual story about the IRI’s work in drought-stricken West Africa.

Earlier that day, Fiondella had interviewed Robertson on his research on improving the prediction capability of water availability in the Himalayas to help water resource managers make better planning decisions. That interview inspired Robertson to see if he could give Fiondella “a taste of his own medicine.”

Video Ambush

Click here to view the embedded video.

 

Andrew Robertson Interview

Click here to view the embedded video.

A River Runs Through It: Predicting Floods in the Midwest

American Geophysical Union Fall Meeting - Fri, 12/07/2012 - 13:58

Andrew Robertson, Head of IRI’s Climate Group

By Elisabeth Gawthrop, Climate and Society ’13

Three of North America’s major rivers run through the Midwestern U.S. In the spring of 2011, major flooding in region caused an estimated $3 billion in damages and killed seven people. Although scientists cannot predict exact precipitation amounts for a given season, they can attempt to predict the odds that a given season will have below average, average, and above average precipitation. If forecasts show an increased likelihood for above average precipitation, the odds of flooding usually increase, too. The International Research Institute for Climate and Society’s Andrew Robertson studies how climate variability across multiple timescales, from daily to decades, affects these forecasts. Using the American Midwest as a case study, Robertson and his colleagues at the Lamont-Doherty Earth Observatory and Columbia Water Center analyzed the relationships between flooding events and weather and climate patterns on multiple timescales over the 20th century. Find out more about how Robertson and his colleagues are trying to improve flood prediction in the Q&A below and stop by his talk at AGU.

 

How do El Niño–Southern Oscillation (ENSO), Madden Julian Oscillation (MJO) and Pacific Decadal Oscillation (PDO) interact to make climate patterns more or less favorable for precipitation in the region?

We have analyzed recurrent daily atmospheric circulation patterns, attempting to link these daily patterns to patterns of longer time scales and covering wider regions and, separately, to extreme floods. We found some weak but statistically significant linkages between weather patterns associated with both floods and ENSO/MJO patterns. La Niña, the cool phase of ENSO, tends to cause a large-scale pattern that’s more conducive to creating the conditions that lead to floods the Midwest. We also found that an active MJO event tends to lead to cause an atmospheric “wave” that passes over the Midwest two weeks following the event. This wave is also conducive to floods. Even though we have a century of records, it’s too short to say much about relationships with the PDO, a phenomenon that shifts over a period of decades as opposed to the monthly and seasonal fluctuations of ENSO and MJO.

What is the skill of your results? Will forecasters be able to incorporate more of these longer time scale variabilities into seasonal forecasts?

The prospects for improved seasonal forecasts are limited because the ENSO linkage is weak. There are better prospects for eventually developing “seamless” forecasts in which forecast information is combined together and capitalizes on the MJO relationships. Particular combinations of ENSO and MJO could lead to better “forecasts of opportunity” in situations where both ENSO and MJO impacts are reinforcing each other.

Is there a human-induced climate change signal that could change these relationships in the future?

The century-long record of floods does not reveal an increasing trend toward more frequent extreme floods over the Midwest signature. Many of the flood events occurred in the early and midcentury, with fewer at the end of the twentieth century.

Why did you focus on precipitation from March through May in the Midwest in particular?

The spring season over the Midwest is a time of heightened flood risk, due to potential confluence of factors conducive to floods. Combinations of snow melt, high ground saturation, and strong interactions between Gulf of Mexico moisture and slow moving cyclones that can occur in the spring lead to increased likelihood of flooding events.

Want more news from the AGU Fall Meeting? Follow IRI on Twitter and like us on Facebook

Clues from Last Ice Age May Hint at Drying Ahead for Some Regions

American Geophysical Union Fall Meeting - Thu, 12/06/2012 - 20:16

Aaron Putnam samples a boulder from Tachanggay Tso moraine in Bhutan. (David Putnam)

In the spectacular collapse of ice sheets as the last ice age ended about 18,000 years ago scientists hope to find clues for what regions may grow drier from human caused global warming. In a talk Thursday at the American Geophysical Union’s annual meeting, Aaron Putnam, a postdoctoral scholar at Columbia University’s Lamont-Doherty Earth Observatory, painted a picture of earth’s dramatic transformation as seen in climate records extracted from ancient cave formations, ice cores, lake shorelines and glacial moraines.

Earth came out of the last ice age in two phases, triggered paradoxically by the cooling of waters in the North Atlantic Ocean, said Putnam. In phase one, the stratification of North Atlantic waters pushed Earth’s wind and rain belts south. The winds caused carbon dioxide to out-gas from the Southern Ocean, rapidly heating the Southern Hemisphere by 16,000 years ago. In phase two, with the evening of temperatures in the polar oceans, the wind and rain belts returned north. By 14,700 years ago, the Northern Hemisphere begins to rapidly warm, bringing the planet as a whole out of the ice age.

At the end of the last ice age, New Zealand glaciers terminated not far from this one pictured with Aaron Putnam in the foreground.

The first interval made normally dry regions wet, and wetter regions, dry, and then the situation reversed 2,000 years later, said Putnam. In the U.S., lake levels in the mid-latitudes swelled as the jet stream pushed south bringing more rain. Lake Lohantan in Nevada and Lake Estancia in New Mexico reached their highest levels about 16,000 years ago, research by Lamont’s Wally Broecker suggests. At the southern edge of the tropical rain belts, Lake Tauca in Bolivia reached its maximum extent at the same time. Meanwhile, the monsoon rains in Asia were failing, leaving evidence of drought in Hulu Cave near Nanjing, China, and Venezuela’s Cariaco Basin. Antarctic ice cores also show evidence of less vigorous vegetation growth in the northern forests. “These are massive changes that are happening,” said Putnam.

The rapid retreat of glaciers in New Zealand suggest that the Southern Hemisphere warmed quickly once the Southern Ocean started to release carbon dioxide.  Moraine dating by Putnam and his Lamont colleagues, Joerg Schaefer and Michael Kaplan, show that glaciers were biggest at 17,800 years ago. In just 2,000 years, the ice retreated close to where it is today and temperatures warmed 3 degrees Celsius, their research shows. (Another degree of warming would happen by the onset of the Holocene 12,000 years ago)

Today, with the North Atlantic now warming, Putnam and his colleagues expect the chain of events to reverse, with wind and rain belts shifting north. “We should anticipate that the dry lands and deserts of the Northern Hemisphere will become drier, which has implications for water resources,” he said. “Monsoons could pick up in South Asia and Venezuela.”

Further reading:

Aaron Putnam’s account of trekking through the Bhutan Himalaya in search of glacial moraines New York Times, November 2012

Study Adds New Clue to How Last Ice Age Ended

Answer to What Ended the Last Ice Age May Be Blowing in the Winds, Paper Says

 

Expanding Our Vision Brings the Big Picture Into Focus

Ice Bridge Blog - Mon, 11/12/2012 - 12:47

Mount Murphy rises through the ice sheet along the flank of West Antarctica, diverting the flow of ice around it (photo credit J. Yungel, NASA IceBridge Project)

1500 feet above the ground surface is where our suite of instruments normally operates, but for this flight we are taking them up higher, much higher, in fact over 20 times our normal range to 33,000 feet. Our flight plan is to repeat lines surveyed in a previous years by NASA’s Land, Vegetation Ice Sensor (LVIS) a scanning laser altimeter. LVIS has collected data as part of the IceBridge instrument suite in the past, but it was flown separately at high altitude on its own plane, in order to map large areas of both land and sea ice. This flight will refly some of LVIS’s work but using a subset of the instruments on our plane, narrow swath-scanning lidar, the digital mapping camera system, the gravimeter, and our depth radar.

At our higher elevation we will fly faster and can cover a lot of ground. The landscape of Antarctica can be hard to get ones head around – a glacier catchment is usually too big to fit into one field of view, so we see it bit by bit, and try to build up a physical picture in the same way we build up our understanding of the system – piece by piece. We have flown several missions into the Amundsen Sea region on the west Antarctic coast in the past, but this was the first time where we could really see the context of all of these different glaciers – flowing into the same embayment, forming ice shelves, calving ice bergs, and drifting northwards through the sea ice.

The flight offers views of some of the most noteworthy features in Antarctica. Pine Island Glacier, one of world’s fastest streaming glaciers, developed an 18 mile crack along its face in the fall of 2011 which spread further over the last few months. The crack will inevitably lead to breakage, dropping an iceberg which scientists have estimated will be close to 300 pound in size.

Crack along the front of the Pine Island Glacier as seen form the IceBridge forward facing camera.


The crack in the Pine Island Glacier as it is propagating further through the ice (Photo credit NASA IceBridge)


Bordering the glacier is one of two shield volcanoes we passed over during our flight. Pushing up through the Antarctic white mask, Mount Murphy diverts the ice streaming along the glacier. A steeply sloped massive 8 million year old peak, Mount Murphy pulls my thoughts back New York as it was named for an Antarctic bird expert from the American Museum of Natural History.

Mount Murphy, one of two shield volcanoes we overflew on this mission. (Photo K. Tinto)


From Mount Murphy we continue to the second shield volcano, Mount Takahe. Ash from 7900 years ago found in an ice core from the neighboring Siple Dome has been attributed to an eruption from this volcano. This massive potentially active volcano is about 780 cubic kms in size. The volcano was named by a science team participating in the International Geophysical Year (1957-8) after the nickname of the plane providing their air support …an unusual name for a plane as its origin is that of a plump indigenous Māori bird from New Zealand which happens to be flightless! Regardless the rather round Mount Takahe soars high above the glacier as we move overtop.

Mt. Takahe a slumbering volcano that is believed to have deposited evidence of an eruption in the ice almost 8000 years ago (Photo K. Tinto)


From there we fly over the tongue of Thwaites Glacier as it calves icebergs into the Amundsen Sea. To read more about Thwaites check out my first blog of the season: http://blogs.ei.columbia.edu/2012/10/18/launching-the-season-with-a-key-mission-icebridge-antarctica-2012/

The calving front of Thwaites Glacier. The neighboring glaciers of Pine Island and Thwaites are moving ice off West Antarctica into the surrounding ocean at a rapid rate (Photo K. Tinto)


For more on the IceBridge project visit:

http://www.nasa.gov/mission_pages/icebridge/index.html

http://www.ldeo.columbia.edu/res/pi/icebridge/:

The Story at Ronne

Ice Bridge Blog - Thu, 11/08/2012 - 14:53

Travel to the Ronne Ice Shelf involved passing by the Ellesworth Mountains. The range contains Antarctica’s highest peak, Vinson Massif at 4897 meters of elevation.

Named after Edith Ronne, the first American woman to set foot on this southern continent, the Ronne Ice Shelf is tucked just to the East of the Antarctic Peninsula on the backside of the Transantarctic Mountains. With an area measured at 422,000 square kms, this is the second largest ice shelf in Antarctica. This vast icy expanse stretches into an indentation in the Antarctic coastline called the Weddell Sea, and gained some attention this past spring when scientists identified a mechanism that will force warming ocean water up against Ronne, which over time will cause it to thin and weaken (Hellmer, H. H. et al., 2012). Ice shelves are important barriers slowing the flux of ice moving off the land into the surrounding ocean. Any weakening in the tight connection of this ice to the land, either at the bottom where the shelf freezes to the ground below or where at the edges where it is tightly fused to the continent, can have major impacts on the speed and volume (flux) of ice moving off the land and into the oceans.

Annotated Antarctic map showing the area of study.


The current mission is being flown to measure the flux of ice currently coming into the Ronne Ice Shelf from the surrounding Antarctic landmass. To determine this we focus on the ‘grounding line’, the area where the ice changes from being frozen solid to the land below to floating as part of the ice shelf. To understand how much ice is moving over the grounding line, we have to understand how much ice is at the grounding line, and to do this we have to fly along the grounding line (or slightly inshore of it).

The majestic Ellsworth Mountains, formed about 190 million years ago, are the highest range in Antarctica, and steeper than the Tetons. Their original name, Sentinel Range, describes their posture, as they watch over the Weddell Sea and the Ronne Ice Shelf.


In many areas of Antarctica, even knowing where the grounding line is takes a lot of work. Much of that work is done using satellite data through a process called “interferometry”. This process compares the returning radar signal from different satellite passes to determine where the ice begins to move under the influence of the ocean tides. In this scale, ice that is responding to the rise and fall of the tides is floating ice, and from this we can mark the grounding line. While technique identifies the grounding line, it does not show how much ice is moving across it; to determine that we need to collect ice thickness measurements. For today’s flight we moved just inland of the grounding line for about half of the Ronne Ice Shelf collecting ice thickness and other supporting data that will begin to fill in this important information.

Reference: Hellmer, H. H. et al. Nature, 2012. DOI:10.1038/nature11064. 


For more on the IceBridge project visit:

http://www.nasa.gov/mission_pages/icebridge/index.html

http://www.ldeo.columbia.edu/res/pi/icebridge/

The Zen of Sanding

The Broadleaf Papers - Sun, 11/04/2012 - 11:56

By Ana Camila Gonzalez

“But can’t you see the rings already?” I ask, wondering why I’ve been asked to sand a sample- it sounds to me like one would damage a sample by subjecting it to the mechanical screech of a sander.

 

“Yes, but under the microscope they look foggy if you don’t sand them. Also, you’re looking at a black oak sample. You wouldn’t see any rings before sanding if you were looking at a Maple, for example.” Jackie responds. She shows me a maple core sample that she explains has been hand-sanded down to a 1200 grit. It’s smooth and shiny as can be; yet I can barely see what seem to be hairlines.

 

“Oh. That makes sense.” I secretly hope I won’t have look at another maple sample for a while.

 

I approach the machine. I look like a character from BioShock or a WWII soldier in the trenches, as I am wearing a respiration mask, goggles and ear muffs. Seemed a little excessive to me at first- once I turned the machine on and I saw the mushroom cloud of sawdust come off the banshee-screeching sander, however, I realized I’d be better off looking like a biohazard worker than having to bring an inhaler and hearing aid to work.

 

Anapocalypse: Ana gearing up for sanding. Image: N. Pederson

 

I place my first sample down on the sander, but it flies off and hits the wall…  I guess I can hold it tighter and push it down a little harder. I try again but this time my sample stops the belt from spinning. Definitely too hard. Eventually I get just the right amount of pressure, and I realize I can tell because my sample looks clearer every time I take it off the belt. I start humming to myself, singing something along the lines of I can see clearly now, the rings are there… As I go to higher and higher grits and my sample starts developing a cloudless luster, I realize I enjoy this a little too much.

 

Ana sanding. Image: N. Pederson

 

To me, sanding is a process full of Zen. It’s a process I can focus on while still letting my mind wander, and my thoughts usually get pretty philosophical- I have this foggy, unclear sample and slowly I take off its layers and layers of disparities. What results is a core in its purest form ready to tell the story of its life, and after a few hours of sanding I’m ready to listen.

Sanded Bhutanese cores. Image: N. Pederson

 

A well-sanded red oak core. Image: N. Pederson

_________

Ana Camila Gonzalez is a first-year environmental science and creative writing student at Columbia University at the Tree Ring Laboratory of Lamont-Doherty Earth Observatory. She will be blogging on the process of tree-ring analysis, from field work to scientific presentations.

 

The ‘Skinny’ on Antarctic Sea Ice

Ice Bridge Blog - Thu, 11/01/2012 - 16:48

Sea Ice on the left, touching up against an ice shelf along West Antarctica. (Photo from the camera in the belly of the plane). The plane is flying at ~1500 ft. of elevation – the estimated field of view is ~450 meters.

One piece of our IceBridge mission focuses on sea ice here in the south. Sea ice in the northern regions has been reducing at dramatic rates over the last decade, setting a new record just this year, but the story in the south is not so clear. In fact, there has been a buzz that Antarctic sea ice extent may just be increasing while the Arctic ice is decreasing. The issue is a complex one and involves not just sea ice extent (how much surface area the ice covers) but sea ice thickness (total volume of ice). While the extent of Antarctic sea ice is increasing, we also need to understand how the thickness is varying.

One of the trickier items in measuring sea ice is making the raw measurements of thicker and thinner ice. With only satellite measurements it is hard to get the true thickness of the ice, since the surface of the ice is often covered with snow that needs to be accounted for in our calculations. Using the snow radar on the IceBridge mission we can work out how much of what the satellite is measuring is actually snow.

Bellinghausen sea ice labeled to show open water (dark areas), dark grey ice (less than 15 cm thick) and thicker light grey ice. Image from the NASA IceBridge camera.


The Bellinghausen Sea sits just to the west of the Antarctic peninsula and in the southern winter months is generally covered with sea ice. We have flown two Bellinghausen sea missions this season – one to map out to the furthest edges and another to looks at the gradient of sea ice change as you move away from the coast or shoreline. The second Bellinghausen mission was important because in running profiles in and out from the coast it allowed us to measure how ice thickness patterns vary with distance from the shore. We need to understand these patterns of ice thickness in the southern end of the planet, how they may be changing and what connection they have to the climate system.

An pice of land ice that has separated as an iceberg (shows with a bluish coloring, approximately 30-40 meters in length) travels trapped amidst the floating sea ice in Bellinghausen Sea, Antarctica.


There has been much less study done on southern sea ice than northern sea ice because we get very few opportunities to make the measurements we need. We have two high priority flights to the Weddell Sea (on the eastern side of the Antarctic peninsula), but so far it has not been possible to fly them because of the weather. Hopefully before the end of this season we will be able to fly both these flights and fill in more pieces in the sea ice story.

For more on the IceBridge project visit:
http://www.nasa.gov/mission_pages/icebridge/index.html
http://www.ldeo.columbia.edu/res/pi/icebridge/

A Recovery Mission

Ice Bridge Blog - Mon, 10/29/2012 - 15:23

Shackleton Ridge bordering the Recovery Ice Stream East Antarctica. (Photo M. Studinger, NASA)

Last year IceBridge had its first flights into East Antarctica when it flew some missions into the Recovery Glacier area. Recovery is a section of Antarctic ice that lies east of the peninsular arm of West Antarctica, tucked behind the Transantarctic Mountains, a dividing line that separates west from east. We know from Satellite data that Recovery and its tributaries have a deep reach, stretching well inland to capture ice and move it out into the Filchner Ice Shelf draining a large section of the East Antarctic ice sheet. But there is a lot we don’t know about Recovery because the remoteness of the area has limited the number of surveys.

Recovery Glacier with the lakes outlined in red. The yellow lines are the flight lines for the mission. (image courtesy of NASA IceBridge)

Several recent works have showed us that this area is important. Satellite measurements of the ice surface show small patches along the trunk of the glacier that are changing elevation more than their surroundings. These patches have been interpreted as lakes that lie under the ice sheet, coined the Recovery Subglacial Lakes. The lakes appear to drain and refill over time as the surface elevation over the lakes changes. To learn more about them and what they might tell us about the behavior of the glacier, we need to look under the ice.

But there is more we need to understand about this remote area, including simply needing to know the size and shape of the channel that delivers this ice out to the ice shelf and towards the Weddell Sea. Last year’s mission gave us some data points to outline the channel, but this year will help us provide a more complete imaging of what lies below this East Antarctic ice conveyor belt.

Recovery Glacier with “Which Way Nunatak” projecting up through the snow. A nunatak refers to an exposed section of ridgeline, or a peak that projects though the ice or snow in an ice field or glacier. (Photo by J. Yungel, NASA IceBridge)

We will fly cross sections along the lines of the retired ICESat satellite tracks, allowing us to compare the laser measurements we make of ice surface elevation to those made during the satellite mission. We will end the day flying along the Recovery channel to get another look at one of the interpreted lakes. Combining last years’ data, ICESat data and this year’s data will give us a better picture of the area that has been carved beneath the Recovery glacier, the amount of ice that can be moved through the glacier and its tributaries, and how the lakes under the ice might fit into the larger story.

Launching the Season with a Key Mission – IceBridge Antarctica 2012

Ice Bridge Blog - Thu, 10/18/2012 - 17:13
Snow blowing off the ice

Snow blowing off the ice and out to sea as we approached our survey site on
a windy day in the Amundsen Sea (30 knot winds were beneath us at times)

October 2012 IceBridge Antarctica resumes … Mission goal…monitoring the polar regions…Mission target… determine changes in ice cover and thickness, refine models for future sea level rise…Mission instruments…airborne geophysics. Good luck team.

The crews have spent the last few weeks in Palmdale, where the DC8 is based, for instrument installation and test flights prior to our move down to Punta Arenas, our home base for IceBridge Antarctica.

View From the DC8

View from the DC-8 as it travels from Santigo to Punta Arenas. Clockwise from top left: forward camera, nadir (directly below) camera, forward bay, aft bay both filled with equipment and supplies.

Instrument Run Down: We are flying with the same instrument suite as last year allowing us to see above, below and through the ice. Laser altimetry, for surface ice measurements, measured by the NASA Airborne Topographic Mapper, visible band photography, to allow for draped imagery, from NASA’s DMS (Digital Mapping System), three radar systems from Cresis to measure the ice thickness, composition and bed imagery (MCoRDS, Snow and KU band) and gravity to refine what is under the ice with Lamont using Sander Geophysics’ AIRGrav gravimeter.

ATM and the gravimeter both require GPS base stations on the ground throughout the deployment. Combined with the GPS receivers on the plane these allow very precise positioning of the aircraft, and the sensors on board, which is critical to all the measurements we make. Setting up the GPS stations is one of the first jobs in Punta Arenas.

Our First Mission for 2012 is Thwaites Glacier – Going Straight to the Heart of the Changes. On our way out of Punta Arenas, out past the airport, I noticed this feature in the landscape:
Paleo Landscape
It appears to be the paleo-shoreline from the last interglacial (~80,000 yr BP), when sea level was higher than present. The very flat terrain results in any sea level change causing a large shoreline retreat. Evidence like this of changing shorelines, is one method scientists use to determine past sea level under a different climate. As we study different areas around the world, we must account for the local changes in how the land has risen or fallen. Changes in sea level can be a combination of an adjusted world/ocean wide (eustatic) sea level and the more local response from the rebounding (isostatic ) of the land that was previously depressed under a glacier as local ice is unloaded during deglaciation. Here the history of the shoreline was governed by a combination of changes in eustatic sea level and the isostatic response to deglaciation of the local ice load (De Muro et al. 2012). Putting together information from around the world we eventually build up a picture of the global changes that have occurred in sea level. Changes in sea level are directly connected to our work monitoring polar ice.

When we fly over the ice, we are monitoring how the ice sheets are changing at present, and learning how to understand the complicated interactions between the atmosphere, the ocean and the ice. Studying this helps us to understand which ice bodies are most likely to contribute to sea level, how quickly they changed in the past, and how quickly they might change in the future. It’s good to get this reminder as we head out on our first flight – especially as it is to survey the area where the glacier switches from being frozen to the land below [the bed] to where it goes afloat, called the ‘grounding line’.

Our first flight of the season will be along the Thwaites Glacier. Thwaites and Pine Island Glacier are two ‘glaciers of interest’, both large outlet glaciers that serve as conduits out of the ice mass of the West Antarctic Ice Sheet (WAIS), moving ice off the land into the surrounding ocean, and long considered its Achilles heel. Thwaites glacier has a very wide region of fast ice flow over its grounding line, and a relatively small change in that width has the potential to greatly increase the flux of ice into the ocean. Through the radar and gravity measurements collected on previous IceBridge missions we have been able to get a sense of the bed shape tipping downward as you move inland from the ice edge, and where pockets of water lie under the icesheet. Our goal today is to collect enough data to develop a more complete image of what lies under the ice in this area.

Image of the inward sloping bed, and the ice front pinning to a rocky ridge. From: Tinto, K. J. and R. E. Bell (2011), Progressive unpinning of Thwaites Glacier from newly identified offshore ridge: Constraints from aerogravity, Geophys. Res. Lett., 38, L20503, doi:10.1029/2011GL049026.

2009 Operation IceBridge surveyed a grid in front of Thwaites grounding line and identified a ridge in the rock of the sea floor. In the last few months a large section of Thwaites glacial tongue broke off just seaward of that ridge. This mission will fly back and forth along nine lines parallel to the grounding line of Thwaites glacier. In combination with flights from previous years, this will give us a map of the grounding zone at 2.5 km spacing.

Thwaites Glacier

Thwaites Glacier from the air. Thwaites Glacier is so low and wide it is hard to get a good picture, but here you can see the fractured area on still-grounded ice where the fast flow is focused. You can also see the tracks from this region being carried out across the floating tongue. The grounding line is marked by the change to brighter white (more broken) ice just below the words “Fastest flow”. The eastern ice shelf is hidden by the wing of the plane, but the broken front of the floating tongue is in approximately the position of the submarine ridge of Tinto & Bell, 2011.

 

The tongue of Thwaites

Image of the tongue of Thwiates Glacier prior to the most recent ice ice section break off. Image from New Hampshire University MODIS Data Viewer tool.

We are hoping to learn more about goes on underneath this icy reach of the Earth each time we take flight.

Dipping your feet in the water (A first year’s experience with fieldwork)

The Broadleaf Papers - Fri, 09/21/2012 - 10:07

By Ana Camila Gonzalez

My feet are soaking wet and I’m playing a game of Marco Polo, but I’m nowhere near a pool. It’s my second day on the job. It’s my second week of college. I have no idea what to expect.

I’m a first year undergraduate student at Columbia University, and I just began to work at the Tree Ring Lab at the Lamont-Doherty Earth Observatory after being told by a few upperclassmen that the Lamont campus “just isn’t for freshmen”.

On Friday, September 21st, several members of the lab headed to New Paltz, NY to do some field sampling for a project aiming to uncover particularly major ecological events in the Eastern United States in the past three hundred years. I had just started to understand the basic concepts of differing tree rings. When I was told we’d be coring trees and identifying them, I smiled and nodded my head enthusiastically. You should see my poker face.

We get to the town of New Paltz and drive right through the center, heading towards Minnewaska State Park.

Looking over a hazed-out Palmaghatt Ravine, the Jurassic Park of Minnewaska State Park, NY. Photo: N. Pederson

After a deceivingly easy one mile hike on road-like paths, we get to the entrance point for the plot that was pre-designated Jackie, Dario, and Neil earlier in the spring. From that point on, I get to witness the transition from a suburban hike to what seems to be the set of Jurassic Park. We’re heading into the area surrounding a ravine, and my feet remind me that I’m not wearing waterproof boots. At some points I feel like I’m in a maze, and I start yelling MARCO! At that point I start remembering that I took the job because I wanted some hands-on experience in the field of environmental science. Grabbing the four-foot fern in front of me, I feel that I’ve made the right choice.

Tromping in the midst of the ‘Jurassic Park’ of the Palmaghatt Ravine. Photo: D. Martin

After some strolling, climbing and maneuvering, we finally reach the plot. Here I finally get to see what the overall project is really about.

While some forest ecosystems in the Western United States recycle nutrients and move through successional cycles at fairly large scales through natural and necessary fires, these processes are much slower and do not seem to occur at larger scales in the temperate forests of the Northeast. Trees experiencing suppressed growth only receive the necessary sunlight, water, and nutrients to experience quicker growth when surrounding competing trees perish, either through logging, disease, windstorms, or similar ecological processes. One can see this change as a drastic change in the width of tree rings: once a previously suppressed tree becomes dominant, the increased growth results in relatively wider tree rings.

When this drastic change is seen not only in the rings of one or two trees but across an entire forest ecosystem, a major ecological event is likely the cause. This project is aiming to find the causes of a few suspected major ecological events in the Eastern United States.

In New Paltz in particular, this project encountered a roadblock- some people believed our study forest in Minnewaska State Park was an old-growth forest, but so far the samples brought back have found evidence of logging in the late 1800s. The first samplings, using plots with a radius of 20 meters, returned few older trees that would be useful to the project. The radius was thus increased to 30 meters, and only trees with diameter greater than 40cm were cored past the 20 meter mark. After this adjustment, the second sampling returned double the amount of older trees. The real science can begin.

A raw increment core. Photo: D. Martin

So here I am, learning all of this for the first time, and I’m fascinated. Another new student and I learn to core a tree, and we realize how physically strenuous it is, laughing about having to lift weights to get in shape for future fieldwork. Like that’s ever going to happen. We’re introduced to a few different tree species during the process, and we begin to learn how to identify them. For the past few days I’ve walked around trying to identify every tree in Morningside Park.

At the end of the day, I’m feeling pretty fulfilled. The way back to the trail isn’t as cinematic as my entrance through Jurassic Park, but I still feel like I won’t get up after sitting down in the car.

Whew – Done for the day! Dario, Javi, Katelyn, Adam, Jackie, Ana, Ale, Jiangfeng rejoice at the end of a hard day’s work in front of a large black cherry. Photo: N. Pederson

That night, I got a rare chance to talk to my cousin, a botanist in Cuba. I told him about my day and he told me that if I start beginning to enjoy science, and the general act of finding answers to questions others might not have thought of asking, it becomes an obsession. He told me I wouldn’t be able to get away from it. I think I’m starting to get a sense of that.   I was hoping to land a job at the LDEO that would just let me begin to get my feet wet in environmental science. So far they’ve gotten soaked, but I have a feeling I’ve only started to dip my feet in the water.

 

Undergraduate research assistant, Ana Gonzalez. Photo: N. Pederson

 

_______

This is the first in a series of guest posts by Ana Gonzalez, a first-year environmental science and creative writing student at Columbia University. Ana is a research assistant at the Tree Ring Laboratory of Lamont-Doherty Earth Observatory who will be blogging on the process of tree-ring analysis starting off with the joys of field work.

 

 

 

Epic Wetness in Greater NYC, and What Broadleaf Trees Have to Say About It

The Broadleaf Papers - Thu, 09/06/2012 - 08:32

2012 is turning out to be an exceptional year in the eastern US. Starting out with what was essentially a #YearWithoutaWinter, followed by a heat wave in March, a hot summer, Macoun and Cortland apples coming in 2-3 weeks early, and the continuation of a severe drought in the Southern US that expanded into the Midwest and Northeast, this year’s climate doesn’t appear ‘normal’. From a 500-year perspective, this year’s drought in the northeast should actually feel like an exception for 58.2% of its people.  While there have been droughts in the Northeast over the last 44 years, trees informed us that, as of 2011, we were living one of the wettest 43-year periods since 1531. It is shocking to see towns flood or covered bridges float away during tropical storms in the northeast. But, our new record suggests that the buildup of soil moisture prior to these storms might make these unusual[?] storms the norm.

Immediately preceding this epic pluvial (a period of increased precipitation) was the 1960s drought,  one of the most intense droughts of the last 500 years. Having lived only during this epic pluvial, I cannot fathom this drought. Pluvial is my norm. So, every time I lead a hike or lab tour on campus, like during Lamont’s great Open House, I always ask if someone was alive during the 1960s drought. Heads tilt back, eyes come alive, and the stories pour out. People talk about tough times and odd events like a landfill catching on fire. I then congratulate them for surviving one of the worst droughts of the last 500 years. Then I have to say, “Uh, but it has been worse. Much worse.”

Often when looking deeper into Earth history, we see things that send shivers up our spine. For those who lived through the 1960s drought, our new record should send shivers up your spine. Our lab’s first study showed the 1960s drought to be the worst since 1700. However, when looking back almost another 200 years, we can say things like, “Yeah, the 1960s drought was bad, but it was only six years in duration.” [six years of below average conditions in our new record] Six years of drought is tough. It must have felt like a decade. But, how might we feel about 23 years of drought? How might a 23-year drought feel when the preceding 11 years had only a few years of average to above average precipitation? [shivers].

The current epic pluvial caps a 150-year wetting trend for the Northeastern US. This trend, however, is not limited to the Northeast. Much of the entire Eastern US has become wetter over the last 150 years. Only the Deep South has trended towards drought over the last 20-30 years.

 

Drought history of five regions in the eastern US. Graphic adapted from Pederson et al., in press.

 

For more on the development of our new record and some of the implications of what we found, go here. The rest of this post focuses on the contribution of biodiversity and broadleaf species to the new record.

Biodiversity, Broadleaf Species, & Tree-ring Reconstructions in Humid Regions

An interesting result of our study was that the use of a greater number of species can improve a tree-ring based reconstruction (for more examples, see here, here, here, here).  Reconstructions have been made using multiple species in humid regions like southeastern NY State since the beginning, so the use of multiple species in not groundbreaking. But, our initial analysis indicates that using 10 records drawn from 10 species outperforms the 10 best chronologies regardless of species (best is defined as the strongest correlation to the climate data used for reconstruction). It seems biodiversity is not only good for life, it can be good for reconstructions of past climate.

We are not exactly sure why increased diversity might improve reconstructions. My pet hypothesis is that each species has a different sensitivity to its environment and that by combining multiple species, differing responses are filtered out, resulting in a more accurate common signal. Some of this is driven by genetics. Some of it could be driven by the ecology of the sites where trees live. Think of it in human terms: some people can eat whatever they want and never gain weight. Some of us look at a banana split and gain two pounds. We might disagree on what we want for dessert, but when offered a fine blueberry pie, or for us sweet tooths – maple cream pie,  we can generally agree if it is righteous. I imagine trees have a similar response.

Remember 1972? Wow, that was a good water year!”

“ Yes, that was a good year, but I really liked 1989.”

“Oh yeah, that was a good year. But what about 1833?”

All 27 records chime in chorus, “Most righteous. Water. Ever!!”

These findings bode well as tree-ring scientists move into new regions of study –  say the rich, temperate, broadleaf forests of Asia, for example. Regions with a vast array of tree species could be a boon for the future of dendroclimatology (the reconstruction of climate from tree rings).

Thinking about how we can improve reconstructions is important. Many scientists are exploring new statistical techniques to extract a chorus of solidarity from trees. From a biological perspective, though, the rate of extinction (literal and functional) is a real threat to our science. Hemlock woolly-adelgid is wiping out hemlock trees, a stalwart species and one of the backbones of the North American Drought Atlas. The loss of hemlock and other important species will thus diminish future reconstructions. Replacements species are needed.

Of the 12 species used in our study, eight are broadleaf species. We found that tuliptree or tulip-poplar (Liriodendron tulipifera) is one of the best species to replace hemlock*. Not only is it drought-sensitive, it has shown to be long-lived: a 512 years old specimen was recently found. Amazingly, only about half of its radius was recovered, as the tree was hollow. I would guess this species can live 600 to 700 years, if not more.

 

Glade and Jacob in front of 512 year old tuliptree, aka tulip-poplar. Photo: N. Pederson

 

Our study also found other broadleaf species suitable for dendroclimatic research. These species include: black birch (for Yanques, but sweet birch for Southerners; Betula lenta), pignut and shagbark hickory (Carya glabra and Cary ovata, respectively), and northern red oak (Quercus rubra). While these trees do not live as long as hemlock or tulip, they are proving to live longer than expected. Continued exploration of species in the diverse eastern North American forest for maximum ages and climatic sensitivity should help dendroclimatological research as species are lost.

________

* Tuliptree is quickly becoming one of my favorite trees. It great longevity is a real treat. It is now the tallest documented tree in eastern North America now, too. But, it is how it handles drought that is so fun. Tuliptree is a drought-deciduous species, meaning that, during drought, it cannot close its stomata as well as other species to staunch the loss of water from its leaves. Therefore, it drops leaves to reduce water loss. If you paid attention to this tree in 2012, you would have noticed yellow leaves in July, a more common leaf color in September.

The really, really cool thing about this species, however, is that it also has indeterminate growth. This means that, unlike many temperate trees, its growth is not limited or set prior to the growing season. I once saw tuliptrees putting on new leaves in September following a dry August. This plasticity is awesome. It also suggests that September Song is not necessarily mournful for tuliptrees.

The light-colored leaves were formed in early September after a dry August in eastern Kentucky. Photo: N. Pederson

The Meaning of Water

In Mongolia, water is energy. Photo: A. Hessl

What is the meaning of water? In my everyday life, water is a given.  Even this year, when at least one quarter of the US has been stricken by drought, water continues to flow from the tap and my family is unaffected by its scarcity.  I remember the California droughts of the 1970s, when my brother and I shared bathwater, I learned not to flush so much, and water was rationed.  Even still, our very sustenance, our wealth was not threatened by the lack of water.  In Mongolia, as in many other developing countries, people depend on water not just to slake their thirst but to sustain their livelihoods.  Mongolian herders must bring their animals to a water body daily.  In times of drought, most lakes dry up, leaving only a few “permanent” lakes available to dozens of herders and thousands (hundreds of thousands?) of animals.  Steppe lakes also serve as virtual “gas stations” for migratory birds and waterfowl – they are hotspots of diversity. Without water, animals perish, food disappears, and people and ecosystems suffer.  In a semi-arid region like the steppe, water allows people and ecosystems to transform solar energy into a mobile and flexible product via photosynthesis and primary consumption by livestock. In Mongolia, water is energy.

John sampling a large lake in Mongolia. Photo: A. Hessl

As part of our new project, we will be collaborating with Avery Cook-Shinneman (University of Washington) to use lake sediments to reconstruct the ecology of lakes and livestock during the Mongol Empire.  Lake sediments can provide a broad array of proxies for past ecosystems.  We plan to use some of these proxies to estimate past water quality and a relatively new proxy, Sporormiella, to assess the numbers of livestock present during the Mongol Empire.  This summer, my student John Burkhart and I visited a number of lakes near the Orkhon Valley, seat of the Mongol Empire, to recon possible sample sites.  In the process, we learned to appreciate the role of permanent lakes in Mongol herders’ livelihoods.

Before leaving for Mongolia, we had worked with Avery to identify more than a dozen lakes to recon.  We were going to collect water and surface sediment samples from each lake to assess their potential.  But upon our arrival in the Orkhon region, we quickly learned that those lakes no longer existed.  The decade-long drought that might be only ending in 2012 had left only a few permanent lakes; we noticed much standing water along the highway compared to 2010.  Though the large lakes we identified on Google Earth were starting to fill up again, the fact that they had dried up during a recent drought suggested they had dried up in the past, leaving only an intermittent record of past ecology.  We began visiting local herders homes (“gers”) to inquire about permanent lakes.

A Mongolian ger (the so-called yurt). PHoto: A. Hessl

We had used this approach before to look for old trees but Mongolians are no better than Americans at identifying old trees.  They always point you to the biggest, most beautiful tree and claim it’s the oldest – when in fact the scraggliest, ugliest tree is usually much older (Editor’s note: Beauty is in the eye of the beholder).  But in the case of lakes, these Mongolian herders were true scholars.  Ask any old herder about where to find permanent lakes, and they will tell you in detail the characteristics of all lakes in their region – when they thaw, when they freeze, what kind of plants grow around it and in it, and how likely it is to dry up.  I should not have been surprised – their life and livelihood depends on their knowledge and careful management of these lakes.

A moist landscape of life in Mongolia. Photo: A. Hessl

This kind of ecological knowledge is not new.  Mongolians have cultivated knowledge of lakes for millennia.  The first permanent lake we visited was less than 5km away from an Uyghur fortress dating to the 8th century.

Ruins of an 8th century Uyghur Empire fortress. Photo: A. Hessl


Categories: TRL

Oceans of Ancient Wood and Coming Full Circle

We have just made it back to Ulaanbaatar after 11 days of in-country travel and field work. While being a bit field worn from working on a lava field for 6 days, we are simultaneously thrilled and in good spirits. It is a bit too early to say, but it seems that Summer 2012 in Mongolia was a success*. It certainly felt like a success to me on the day we came full circle from 2010.

Amy, John, and Sanaa were a day ahead of us and, with John being down with a case of Chinggis’ revenge, Amy and Sanaa spent a full day on the lava field revisiting and re-visioning how we would sample over the following week. The hopeful goal was to collect enough wood to push the chronology near 2000 years in length while having enough samples over the last 1000 years to be able to say something with statistical significance. Sanaa and Amy intensely studied where to find wood and what pieces might be from an earlier era. They accomplished this while collecting 24 cross-sections of deadwood. It was an impressive and hugely helpful first day.

It was necessary to study the characteristics of the deadwood and its geographic distribution across the lava field because, honestly, our first discovery is pretty much the definition of, “a blind hog will find an acorn every once in a while“. During Amy’s and Sanaa’s first day of discovery in 2012, Sanaa came up with the term ‘ocean’ for the large, open areas of lava that are virtually devoid of trees. Because the ocean as a whole can be considered a kind of desert, we found that term ‘ocean’ was correct: this part of the lava field truly resembled a desert. Thus, over the course of our fieldwork, the first verse and drifting characteristics of A Horse with No Name came to mind. The heat was hot. There were plants and birds and rocks and things. Oh yeah, there were a few rocks.

A 360 pan of a large ‘ocean’ of lava. Can you spot Amy and Kevin? Photo: N. Pederson

Together we learned that it was on the margins of these oceans that we could find what appeared to be ancient wood. It wasn’t until the penultimate day, however, that we had any sense of what we had accomplished.

Being 5 days in and having collected ~150 pieces of deadwood, we were all a bit burnt, literally and figuratively. Though we had sunscreen and hats, it wasn’t quite enough. We all looked a bit beety. We were also running on fumes. Constantly hiking on jumbled and sharp pieces of lava jars the body and mind. So, on Day 5 we set out for a low-pressure ‘cleanup’ of the lava field. Almost anything we collected that day would be bonus material.

We decided to head towards some of the sample locations from 2010 to see if we could find some of the oldest pieces. Many of the oldest pine cross-sections from 2010 were not GPS’ed due to time, energy, and the afterthought nature of that collection. So, on Day 5 in 2012 we wandering an area we mostly missed in 2012 while at the same time trying to recollect the hazy afternoon in 2010.

About 45 minutes to an hour in, we had our first success. We re-discovered ‘The Logo Tree’. While the day on the lava field in 2010 is still very hazy in my mind (due to my state of being in day 3 of undiagnosed and untreated tonsillitis), the sharpest memory of that day is The Logo Tree.

The Logo Tree, a dead and likely ancient Siberian pine. Photo: N. Pederson

In 2010 The Logo Tree symbolized the potential for this site. We had spotted some Siberian pine trees, a species I did not see during my first brief visit to this site in 1999 with Gordon Jacoby, Baatarbileg Nachin, and Oyunsanaa (Sanaa) Byambasuren. This tree, though dead, captures many of the characteristics of old trees (charismatic megaflora) while also having the weathered, ‘stressed’ form of trees living on the edge of survival. These trees are often the ones tree-ring scientists use to reconstruct past climate. The Logo Tree screamed, “I, and many other pines like me, are ancient. You might better pay attention. This area could be filled with xylemite.”

So, it was with great joy that on Day 5 of 2012 The Logo Tree was re-discovered. Many picture were taken. Champagne corks were unleashed (in the form of taking the top off our water bottles and taking a swig of water). It certainly lifted me to a higher energy state.

We then spent much of the next few hours scouting for more samples from 2010 and passing through what can be considered a pine graveyard, an area filled with much deadwood and ancient, stunted pine trees.

Three generations of trees in the ‘pine graveyard’: deadwood, ancient, but stunted living trees, and tall, spritely young trees. Photo: N. Pederson

A specific goal on Day 5 was to locate the oldest piece from 2010, a sample dating to the middle portion of the first millennium of the Common Era. Having not yet found it as the day was drawing to a close, we decided to narrowly focus on finding that piece. We wandered. We scratched our heads. We saw a horse with no name. And then…and then, we hit an area with signs of our past chainsaw work.

Could it be? Might that be The One?

Yes, it had to be. See, that sample, The Eldest of 2010, sits near my desk. It is within arm’s reach in case of impromptu lab tours. I know that sample. The Elder is a bit oval with a characteristic hole that makes it easier to carry or hold up with two fingers. This seemed to be it.

The joy and shock of this confirmation, of coming full circle, was that this log didn’t look as old or as weathered as many of the pieces we had collected over the prior 4.75 days. It didn’t look exceptional. It nearby cousin, cut 2/3rds of the up a dead stem, was equally unimpressive. Yet, The Elder’s cousin dates to the late-1200s.

Sanaa, Amy, and Neil with The Elder, Day 5, 2012. Photo: B. Nachin

This particular re-discovery floated us for the remainder of the day and trip back to Ulaanbaatar. We cannot yet say with any certainty, but it seems we really hit our research goal. In fact, we are now concerned that we might have some pieces so old that they will not date – they might actually predate any long chronology we might build from this site. But, if this is a problem, we wish this kind of problem to all of our colleagues.

Now, to some scenes from the field:

Hi ho, hi ho, it’s off to work we go. Photo: N. Pederson

Neil and Amy, ocean walking. Photo: K. Anchukaitis

Amy sawing a piece of dead wood on the edge of a sea of lava. Photo: N. Pederson

Sample KHO415. Photo: K. Anchukaitis

John taking a plunge cut from a snag. In addition to taking samples from logs, we took some samples from standing dead trees. Photo: N. Pederson

Some snags took on a colorful beauty. Photo: N. Pederson

Some of the ancient-looking pines were quite short compared to their compatriots. For example, Amy is ~1.6 m tall. The 400? 500+? yr old pine to the left of Amy might be a little over twice her height. Photo: N. Pederson

Despite being low in productivity, the lava field holds much life. Can you spot the wolf scat? Photo: N. Pederson

Kevin says, “You’re still here? It’s over. Go home. Go.”** Photo: N. Pederson

*No living trees were harmed in the creation of this post

** respect


Categories: TRL

Brief Broadleaf Forest Happenings: tulip goodness, delighted about Turkey, and drought

The Broadleaf Papers - Sun, 07/29/2012 - 08:12

I have to call myself out. Earlier I had professed to being a former coniferphile. That was, of course, silly. I like coniferous trees very much. Half of my business is made from this lovely branch of the tree family. This introduction is a lead in to say that this blog will be quieter while my gig in Mongolia continues. A team of us are off to Mongolia to recover an millennia or two of xylemite. My focus in August and September will be on the development of a tasty and long record of drought from central Mongolia. You can follow these adventures here. Before I make that switch, I wanted to make a brief update on a good, busy summer.

Update #1: I caught a tweet that indicated that angiosperms have the ability to adapt a wee bit quicker than conifers. Looking forward to that line of work!

Update #2 – This summer our lab hosted two Lamont Summer Interns. Jackie Testani worked with me and Dario Martin-Benito on understanding the long-term forest dynamics of the Palmaghatt Ravine in the mid-Hudson Valley, NY. When first viewed from the west, the Palmaghatt made me think that if I re-labeled the image below as Borneo, folks would ooh and ahh. The light-green pyramidal crowns of the tuliptrees (Liriodendron tulipifera) gave me the feeling many people have about tropical forests: luscious, wild forest.

Looking east over the Palmaghatt Ravine. Photo: N. Pederson

 

  Jackie has completed some impressive work this summer. A history major with an interest in medical sciences and Africa, she has taken to tree rings like nobody’s business. Most impressively, Jackie slew the zombie maples. See, a small, but not insignificant proportion red maple in the northeastern US tend to not produce growth rings in the decade or two prior to coring. This on top of red maple’s diffuse-porous rings makes it difficult to work. The cause for the zombie’ness is not yet so clear. But, it happens. Often. Jackie’s work matches an independent collection of red maple from the 1980s. Both show some trees missing 5-6 rings in the decade or two prior to coring. This has important implications for all kinds of tree-ring based research.

An impressive red maple. Photo: N. Pederson

  While the Palmaghatt was generally considered to be an old-growth forest, our preliminary evidence indicates some significant logging in the late-1800s. This event was confirmed by the good folks at the Mohonk Preserve who have the best and, likely longest, observations of the environment in the region.

Massive black cherry & field crue. Jackie is on the far right. Photo: N. Pederson

 

And, to finish this update (as we approach the Christmas season), we also found a porcupine in a birch tree.

 

And a porcupine in a birch tree. Photo: J. Martin

 

Update #3 – We has also gotten some preliminary dates on the samples from Turkey. Dr. Nesibe Kose and her students have done a nice job in making their way through the collection. A spruce and fir tree is more than 200 years old. The limited beech forests that we could reach during fieldwork are wicked-fast growers and not too old – 100-180 years old. The oaks look to date to the mid to late-1700s. The coolest thing is that the umbrella pine have a large age range, from ~100 years to >210 years of age. So, these ages suggest this stand was not planted by Russians in the late-1800s. However, when in Eurasia, you can never be too sure this stand was not planted at some point in time. If these ages hold, it suggests that, regardless of their origin, they comprise a functioning stand with little stand-scale disturbance.

Update #4 – I will use this blog to call attention to some neat pieces of the literature in broadleaf forests. Bob Booth and colleagues have a 2012 paper indicating that changes in moisture availability in the Great Lakes region, a relatively humid region, plays a strong role in forest dynamics. Particularly, changes in moisture lead to a long-term decline in American beech. There is also some indication that snowpack is beneficial to sugar maple. You like maple syrup? If so, let’s hope that the snowless 2012-2013 Winter does not become a climatic habit.

Update #5 – Speaking of drought, the drought in the southern US has crept its way into the northeast Maybe The South will rise again? ;). The US drought monitor for July 24, 2012 shows drought across much of the US. Here in NY, the drought came fast and seems exacerbated with the successive heat waves this summer. This year’s growing-season drought is in stark contrast to 2011, one of the wetter years since 1531 (a paper just accepted in the Journal of Climate). If you are lucky to live in the range of tuliptree, however, you do not need an internet connection to know the severity of drought in your area. Go seek the tulip tree. Being a drought-deciduous tree, some of its leaves yellow and fall during drought. It almost seems like a 10% increase in the ratio of yellow leaves to green leaves equals one unit of the Palmer Drought Severity Index.

A green tuliptree turning yellow with the early-July drought. Photo: N. Pederson

Finally, update #6 – I just came across a paper by the White Lab suggesting that southern Magnolia (Magnolia grandiflora), or bull bay, is becoming naturalized to the north and west of its range  (The South will rise again, II?). The implications in the paper is that warmer winters are allowing this iconic Tree of the South to expand its range.  If you find yourself near Auburn, AL, find your way to the Bartram Trail. It will take you through some spectacular forest-grown southern Magnolia. They look much different than the ones you see in people’s yards. When in this form, it is one of my favorite trees.

What Would Chinggis Do?

Saturday dawned a beautiful morning the air was crisp and cool, all of Mongolia had just gotten up at 4 in the morning to watch the opening ceremonies of the London Olympics, and traffic was light.  It seemed an auspicious beginning for our 2012 field work.  The opening ceremonies for our fieldwork had never run so smoothly: Baatar had arranged for our favorite driver, Chukha, to meet us at our hotel at 9am to get an early start.  It would be a solid 6-8 hour drive to the first lake we wished to sample Oygi Nuur, 9am did not seem too early. Drs. Baatar and Sanaa plus an undergraduate student, Balja, packed Chukha’s Russian military van at an astounding 7am (does Chukha really get up that early?) allowing us to leave Ulaanbaatar less than 36 hours after we arrived.  It was truly unprecedented.

Chinggis seated at the front of the Mongolian Parliament. Photo: N. Pederson

We made several stops on our way out of town, additional groceries, toothpaste, fuel, bar oil for chainsaws and a fruitless search for distilled water (why would we think we could get that here?) but we were still headed out of the smog bubble that is UB before noon.  It was a bit later than I had hoped, but still remarkable given our previous trips when it had taken several days to resist the gravitational force of the city.  As we left UB and the smog behind, we began to see small signs of the countryside: a few gers (circular felt tents), small herds of sheep for sale, and a couple of trucks loaded with wool.  John, my new PhD student, even saw his first Mongolian horses.  We could literally taste the Mongolian countryside.

Tsagaan takhi in northern Mongolia. Photo: N. Pederson

But as we drove up the last rise out of the Tuul River valley, the van sputtered, then stalled.  Things seemed routine Chukha was under the van in no time complaining of a loose battery connection.  In 15 minutes we were back on the road. At the next rise, the van stalled again, and this time Chukha looked truly distraught.  The rest of us piled out of the van, had a picnic lunch, and watched Mongolia clouds.  Chukha emerged from under the van looking like his best dog had just died.  He couldn’t eat, didn’t want to talk.  His van had literally blown a gasket.

On our way back to UB, after a beer and a couple shots with Chukha, we did our best to keep our chins up.  After all, what would Chinggis do?  We would try again tomorrow.  Until then, here’s looking forward to dinner.


Categories: TRL

Pages

 

Subscribe to Lamont-Doherty Earth Observatory aggregator