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.
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.
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.”
Aaron Putnam’s account of trekking through the Bhutan Himalaya in search of glacial moraines New York Times, November 2012
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.
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.
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.
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/
For more on the IceBridge project visit:
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).
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:
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.
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.
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.
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.
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.
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.
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:
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.
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.
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.
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.
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:
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.
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.
We are hoping to learn more about goes on underneath this icy reach of the Earth each time we take flight.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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:
*No living trees were harmed in the creation of this post
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.
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.
And, to finish this update (as we approach the Christmas season), we also found a porcupine in a birch tree.
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.
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.
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.
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.
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.
People have been looking for 800 years. Looking for Chinggis Khaan, né Ghengis Khan. From the people searching for his birthplace to the people searching for his last resting place. After more than 800 years since his rise from the mountains of Mongolia, Chinggis lives on as a charismatic and almost mythical person. He seemingly rose from obscurity, quelled feuds between tribes, and created the largest land empire in world history. If you read beyond what you likely learned in high school or college, you will see his leadership skills were progressive and exceptional. You will learn that Chinggis has an influence on our world nearly 800 years after his death. From paper money to the pony express, from war strategy to the structure of the human genome, his life has touched generations of humans over the centuries.
When you begin working in Mongolia it is absolutely essential that you learn the importance of the man. Soviet communism attempted to quell his spirit and his importance in Mongolian culture. Mongolians were not allowed last names so everyone could be equal, so no one could trace their family history to the royal family. This, of course, did not work. In a culture that has songs and stories dating back centuries, if you, a native Mongolian, meet a stranger in the woods on the other side of the country and drink tea, break bread, and just lounge, you will soon break into a song that you and the stranger know from the depth of your soul. You will sing, smile, and enjoy a wonderful afternoon with this once distant, now close cousin. That kind of cultural bind does not break under any kind of political pressure. Perhaps it only made it stronger? See, in the late-1990s, soon after the fall of communism, Chinggis essentially rose from the ashes. He was everywhere in Mongolia – TV commercials for cell phones or a brand of vodka. And once you, as an outsider, spend considerable time in Mongolia, especially during Naadam and especially in the open Gobi steppe with people who still live as their ancestors did centuries ago, you understand the importance of the man and you will also begin to chase Chinggis. And, it is with this new project that our group of geographers, paleoclimatologists, ecologists, historians, and ecosystem modelers begin our pursuit of Chinggis Khaan.
Unlike other chasers who came before us, our search for Chinggis is not directly a pursuit of him as an individual. We understand he was an incredible leader who was the life force for the great Mongol Empire. Our pursuit is more contextual. We seek to understand the environmental conditions before, during, and after the rise of the Mongol Empire. In many ways, the success of the Mongol Empire is a historical enigma. At its peak during the 13th century, the empire controlled areas from the Hungarian grasslands to southern Asia and Persia. Powered by domesticated livestock, the Mongol Empire grew at the expense of farmers in Eastern Europe, Persia, and China. Two commonly asked questions of this empire are “What environmental factors contributed to the rise of the Mongols?, and “What factors influenced the disintegration of the empire by 1300 CE? . For a long time (centuries?), it was thought that drought partly drove the Mongols on their conquest in Eurasia. Luckily enough for us, a serendipitous collection of a few pieces of deadwood and old Siberian pine trees suggests essentially the opposite. Our collection of an annual record of drought, currently dating to the mid-600s CE, suggests that the early-1200s were unusually wet. Of course, these findings are very, very, very preliminary – we only have two trees through this time period.
So, with funding from the Lamont Climate Center, National Geographic Society, West Virginia University, and the Dynamics of Coupled Natural and Human Systems program of the National Science Foundation, we are headed back to Mongolia for a fourth straight year to scour the study site that yielded a 1,300 year record for more old, dead wood. With a combined crew from the National University of Mongolia, West Virginia University, and the Tree Ring Laboratory of Lamont-Doherty Observatory, Columbia University and the Earth Institute, we will spend 10 days in the field seeking, documenting, and collecting wooden gold, xylemite if you will.
Part of our crew will also spend about three days at upper tree line on a mountain in the western Khangai Uul (uul is Mongolian for mountain) updating and expanding the collection that suggested that it was warmer during the rise of the Mongol Empire. We are so excited. We have a great crew, will be spending our time mostly in one place, and will have some of the finest scenery in Mongolia in our eyes everyday.
Frankly, we are also excited about our larger project. We honestly do not know what the end results will be. The idea that wet conditions aided the expansion of the Mongol Empire is simply a hypothesis built upon ecosystem ecology, human ecology, and our preliminary results. See, energy is critical for human and natural systems to function, yet few studies have examined the role of energy in the success and failure of past societies. Increased rainfall on the Great Gobi Steppe should allow the grassland to capture more solar energy. Greater grass production logically would have allowed the Mongol Empire to capture, transform, and allocate this energy through their sheep, horses, yak, etc. In turn, this should have allowed greater energy from which Chinggis could develop a larger and more complex social, economic, and political system.
Feeding tree ring based climate history into an ecological model, we plan to investigate how past climate influenced grassland productivity, herbivores, and, thus, energy flow through the Mongol ecosystem. These data will be compared to historical records on the empire and sediment records from lakes that can estimate herbivore density.
Much has been made about the demise of cultures as a result of a downturn in climate or degradation of their environment. Our estimates of energy availability and environmental quality allows us to investigate whether the contraction of the empire was related to drought, cold, declining grassland productivity, or poor water quality associated with rapid urbanization and climate change.Thus, as part of our larger project, we will test the hypothesis that the arc of the Mongol Empire was influenced by the energy available to nomadic pastoralists for building a mobile military and governmental force sufficient to conquer and govern a significant portion of Asia and Eastern Europe.
We leave in less than two weeks. As happens each year around this time, memories of past trips are revived and we begin seeping back into the Monglish culture that develop on these trips. We look forward to re-uniting with colleagues like Baatarbileg Nachin and his students like Bayaraa. A highlight this year will be working alongside a Mongolian postdoc, Sanaa, who Neil met as an undergrad in 1998. It will be an honor and pleasure to work with Sanaa again. Mongol phrases and words are bubbling up from the depths of our grey matter. Mongolian music is spinning nearly full-time in one household; a soundtrack for this year’s fieldwork is coming into shape.
We hope to catch a set of Altan Urag, a rising rock band in Mongolia. To us, they represent some of the cultural struggle in Mongolia today: “How to we maintain the qualities we are so proud of during the height of our empire, as new or external culture moves into our land?” and “As commercialization in the post-communism era (including a ‘gold-rush’ in the mining industry that created one of the fastest growing economies in the world) pushes and pulls us, how do we maintain who we are?” Altan Urag and young Mongolian artists are reaching back in their history for symbols and sounds that make them distinctly Mongolian. At the same time, these artists keep their eyes and ears open to the new possibilities of their larger world. Similar to how Chinggis melded European and Chinese technology to forge his great empire, many of today’s young Mongolians blend their history with external elements to create a new Mongolia. We cheer these efforts on. We are big fans.
By Steve Holbrook
(Active blog at: http://cascadiaseismic.blogspot.com)
The RV Langseth is continuing work in the Cascadia subduction zone region with the COAST (Cascadia Open Access Seismic Transects) project. We are a scientific team of 20 scientists currently aboard the R/V Langseth, acquiring seismic images of the Cascadia subduction zone. Through our work we hope to provide new insights on the position and structure of the plate boundary between the downgoing Juan de Fuca plate and the overlying North American plate.
This plate boundary is unusually enigmatic, because it produces fewer regular earthquakes than most subduction zones. Tsunami and paleoseismic data suggest that this subduction zone is capable of generating earthquakes up to magnitude ~9, so understanding the position and morphology of the plate boundary is important for obvious reasons. In addition, we’ll produce images of the mechanical structure and fluid pathways in the subduction system – all of which provides important information on seismic hazards and subduction processes. You can read more about the science on our blog at http://cascadiaseismic.blogspot.com …But here I’d like to introduce you to our team and a few of the unique aspects of our project.
This project was originally conceived at a community workshop held in Incline Village, Nevada, two years ago. At that meeting, the marine seismic community brainstormed on ways to make our data more open and accessible to a broader range of stakeholders (students, researchers, teachers, and the public at large). One part of the strategy adopted at that workshop was to support open-access data sets, acquired on open-participation cruises. This cruise is a first step in that direction. What’s unique about our project is (1) cruise participants were selected from open applications, and (2) both the raw and processed data we produce will be immediately publicly released, so that anyone can use the data (including writing proposals to work on the data). The shipboard science team consists of three of the PI’s (Steve, Katie, and Graham), plus a crack squad of 17 students, postdocs, and young faculty from around the country. (The PI’s have taken to calling these participants the BYT’s, or Bright Young Things.) Those folks will be introducing themselves to you through this blog, but I can tell you that we have participants from fourteen different organizations (twelve universities and two different USGS offices), comprising 13 graduate students, 2 postdocs, and 5 faculty. The Lamont folks tell us, with feigned enthusiasm, that we have set a record for the number of cruise participants (55 in all): we’ve filled every bunk on the ship. Fortunately it’s a short cruise (12 days)!
On our blog we’ll talk about the science we’re doing, introduce the Langseth, show some initial results, and hear from our BYT’s. Give it a visit!
By Geoff Abers
While the R/V Langseth plies the waters offshore the Pacific Northwest, we have been recording its source with seismic equipment on land. Lamont ran seismometers in Washington, deployed by two Columbia graduate students, Helen Janiszewski and Zach Eilon, and myself, and received some “logistical support” (shovels, batteries) from colleagues at the University of Washington. Anne Trehu of Oregon State led a parallel Oregon deployment. Like the Langseth, we are making use of national shared instruments; our gear comes from the PASSCAL Instrument Center in Socorro, NM, a facility of the Incorporated Research Institutions for Seismology and supported by the National Science Foundation. Writing this reminds me that modern science tends toward major collaborations; most field seismologists nowadays have to be masters of logistics. Much of my job was negotiating with myriad landowners to get permission to place our (small) equipment on their land, including timber companies, state agencies, civil safety organizations and even people with big backyards.
Our sensors record the same seismic signals as the ocean bottom seismometers the R/V Oceanus deployed, and we will combine the data later. They can detect Langseth signals up to 100 miles inland! This is something extraordinary, and difficult to believe until seen. The on-land data allows the project to extend over and past the fault zone that underlies the coast off Washington and Oregon, the Cascadia Megathrust. While the existence of the fault has been long recognized, growing evidence suggests that this fault is building up strain, and is capable of generating great (magnitude 9) earthquakes. Still, unlike most other subduction zone faults there are almost no small earthquakes on it, and so we know relatively little about it. The signals from the Langseth will reflect off the fault, at 15 – 20 miles depth near the shoreline, and be recorded on the seismometers we deploy farther west. The reflections should tell us a great deal about the thickness and internal structure of the fault zone, and the nature of the rocks on either side. While we cannot predict earthquakes, these data help test physical models of what active faults are like deep in the earth where we cannot otherwise see them.
In mid-June we recorded data in Washington from the Langseth far offshore, and in early July the Oregon group did the same. The Washington work should be completed in a second phase in mid-July. All of this means lots of trips and a good deal of time driving between the Washington beaches and the Mt Rainier foothills. Most of our sites are in recent clearcuts accessed via logging roads, so we can avoid large trees that occupy the rest of the Northwest (they shake the ground too much and block GPS signals). The clearcuts are old and the roads are not used much, so we spend much time clearing branches and cutting small trees that fell across the road to get to our sites. My students did not expect they would be lumberjacks when they came to grad school in New York!
At the end of the first deployment we met the Langseth in Astoria. We had been driving the biggest SUV that I could find – a large Suburban capable of carrying seismic equipment, big batteries, tools, and people, over any road. Nevertheless, next to the Langseth, the Suburban is very small. Stepping across the shoreline to do science clearly requires a whole other scale of operation.
Geoff Abers is associate director of the Seismology, Geology and Tectonophysics division of the Lamont-Doherty Earth Observatory.
After a day of coring on Tuesday, we decided to give our arms and backs a rest and collect water and plant samples. We take these samples so that we can characterize the chemical signatures of each plant type, and water from different parts of the system. Then, we can recognize those same signatures in the samples we take from our core. We can use the chemical signatures of the core samples to reconstruct how the vegetation and distribution of moisture has changed in the peatland through time.
While we were collecting our samples, we had a chance to meet some of the characteristic tundra wildlife.
By Helene Carton
As part of our study of the Juan de Fuca plate from its birth at the mid-ocean ridge to its recycling at the Cascadia subduction zone, the R/V Oceanus has the task of conducting Ocean Bottom Seismometer (OBS) operations and oceanographic measurements: this is done in close coordination with the R/V Langseth, which tows the high-quality sound source used to generate the waves that the OBS listen to.
The Chief Scientist Pablo Canales from Woods Hole Oceanographic Institution, three graduate and undergraduate students from Boston College, CSIC Barcelona in Spain, and Dalhousie University in Canada, and myself from LDEO boarded the ship at the Oregon State University Hatfield Marine Science Center on Yaquina Bay on sunny June 6. The two teams of OBS engineers from Woods Hole and Scripps Institution of Oceanography were onboard, and all the ocean bottom seismometers had been loaded, some neatly aligned on racks on the deck, others stored inside a dedicated container. The CTD (conductivity-temperature-depth) instrument stood firmly secure on deck, wrapped in its protective bag. Looking forward to our departure the next morning, we enjoyed some delicious seafood meals onshore.
The course of operations has us visit a series of eighty-five “sites” carefully defined ahead of the cruise, typically located about ten miles away from one another, identified as red, blue and yellow dots on the colorful map of the seafloor topography on display in the ship’s main lab. In between sites the ship transits at a speed of about 11 mph. While at a site, we are either deploying an ocean bottom seismometer (dropping it off the side of the ship using a crane), interrogating it to get its precise coordinates on the ocean floor, picking it up using long poles equipped with a hook at the end, or sending the CTD instrument probe the water column all the way down to 20 meters above the sea bottom and then bringing it back up.
Our small science team has been keeping itself busy, with duties involving helping with deployment and recovery operations on deck (and occasionally getting our pants and hard-toed shoes soaked!), processing the CTD measurements to better understand the movements of water masses in this region of the NE Pacific, and taking a preliminary look at data downloaded from seismometers that, a few days ago, were still listening for sound waves at the sea bottom under 2000 meters of water.
Several times we have crossed paths with the R/V Langseth while she was towing equipment and recording data, and remained a precautionary distance of several miles away: in lieu of waving from the deck, watchstanders on one ship greeted watchstanders on the other ship through messages in our mutually-visible electronic logs!
In the course of our time at sea so far, we have seen whales, seals, dolphins, porpoises, and birds. Towards the end of our first suite of CTD casts, the sensors got intruded by jellyfish, which resulted in some unusually wiggly signals. We have also seen (and sometimes picked up!) a variety of floating debris, perhaps from the tsunami that struck the Japanese coast in March 2011. After traveling through the Pacific Ocean such debris have started washing ashore on the beaches of Oregon.
Our adventure at sea continues until July 14 (after a brief port stop in Newport conveniently timed to coincide with the July 4 holiday!), with the final recoveries of all the OBS.
Our first day in the field was a wild success! We visited Imnavait Creek Peatland, named for the small stream that drains out of it into the Kuparuk River. We chose this location because it has the potential to be much older than many other peatland sites. During the last ice age, the area of the creek escaped being scoured away by a glacier, so could have been accumulating sediment during that time. Unfortunately, previous attempts to recover cores that reached these old sediments were hindered by equipment failures. This time, we used an auger specially designed to core permafrost soils, and we were able to core more than two meters of sediment, about a half meter more than had previously been achieved. Hopefully the additional sediment will allow us to understand how peat accumulation differs during ice ages. We won’t know exactly how old the sediments are until we get our cores back to the lab and determine their ages using carbon-14 dating. Stay tuned! See a video of us using the permafrost auger below.