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Imaging the Cascadia Subduction Zone

Cascadia in Motion - Tue, 06/19/2012 - 11:55

The Langseth will image the subduction zone off Washington, Oregon and British Columbia that is capable of producing megathrust quakes.

Off the coast of Washington and Oregon, the Juan de Fuca plate dives under North America, slowly descending back into the mantle from which it was formed only 8 to 10 million years ago–very young in the context of earth history!. As the plate descends, stresses accumulate within the fault zone dividing these two tectonic plates which will eventually result in a large megathrust earthquake like the devastating Tohoku earthquake offshore Japan in 2011.

In the research expedition now underway, we will investigate the plate before it disappears under North America to understand why earthquakes happen where and when they do within this Cascadia subduction zone.

During our cruise we are using sound to probe the sub-seafloor, to generate images that tell us about the properties of the oceanic crust and mantle that lie beneath. Our soundings can penetrate through the several kilometers of sediments that cover the Juan de Fuca plate, into the 6 kilometers thick crust and  below, into the upper part of the earth’s mantle.

Students and scientists (Suzanne Carbotte, far right) before departing Astoria, Ore.

Our ship, the R/V Marcus G. Langseth, is one of 25 research vessels available to U.S. scientists for oceanographic research. The Langseth is unique among the research fleet, equipped for advanced seismic imaging, with a high quality sound source and long arrays of listening devices, or hydrophones, which trail behind the ship listening for the echos returned from the seafloor and below.

Our program is complex. Part of our science team is on a companion ship nearby, the R/V Oceanus, deploying ocean bottom seismometers, which are also listening to the Langseth’s soundings. On land, just prior to our cruise, a series of seismometers were set out by our colleagues in the mountains of coastal Oregon and Washington to also record our soundings. With these arrays, extending hundreds of kilometers offshore and onshore, we hope to see deep into the subduction zone in two regions with quite different properties, one along the Washington margin where there are relatively frequent small magnitude earthquakes ,and the much quieter central Oregon margin.

This expedition features a cast of scientists and graduate students from the U.S., Canada, France, China, Spain and Serbia. We are accompanied by expert science technicians who deploy the advanced seismic equipment, marine mammal observers who let us know when marine mammals are nearby, and the crew who ensure the safe operation of our ship, day in and day out, for the 26 days we will be out on the cloudy Northeast Pacific.

This sound-source dropped overboard will allow scientists to image the sub-seafloor. (Greg Horning, WHOI)

Lamont-Doherty Earth Observatory: Milestones in Climate Science

The 2015 Paris Climate Summit - Thu, 06/14/2012 - 14:41

(Note: This feature first appeared in 2012; it was updated November 2015 for the Paris Climate Summit.)

Much of the modern understanding of climate has been shaped by pioneering studies done at Columbia University’s Lamont-Doherty Earth Observatory. Starting in the 1950s and extending through today, researchers in oceanography, atmospheric physics, geochemistry and other disciplines have shown how natural climate cycles work; how carbon dioxide is now influencing earth’s temperature; the hidden roles that oceans play in regulating climate; and, most recently, how ongoing rapid climate change is affecting nature and human societies. Here is a timeline of studies that have changed the way the world looks at climate.

Climates of the distant past are often studied using cores taken from ocean bottoms; Lamont scientists have been the leaders in collecting and studying these, and the institution holds the world’s largest repository. Above, deputy director J. Lamar Worzel and director Maurice Ewing on the research vessel Glomar Challenger, 1968.

1956: A theory of ice ages Maurice Ewing and William Donn, Science   Maurice “Doc” Ewing, one of the world’s most influential oceanographers and Lamont’s first director, teamed with geologist Donn to propose that ice ages are driven by self-perpetuating natural cycles of freezing and thawing of the Arctic Ocean. This paper and two followups were seized upon in popular literature of the time to suggest that a new ice age would arrive soon. Although scientists’ views shifted radically as more evidence came in, this initiated Lamont’s tradition of studying large-scale climate swings.

1960: Natural radiocarbon in the Atlantic Ocean Wallace Broecker et al., Journal of Geophysical Research   Wallace Broecker, one of the founders of modern climate science, showed how isotopes of carbon produced by natural and human processes could be used to map ocean currents that we now know form a series of global-scale loops. This led to an overarching model of the “Great Ocean Conveyor Belt” and the idea that changes in the conveyor may bring sudden, powerful shifts in the global climate.

1966: Paleomagnetic study of Antarctic deep-sea cores Neil Opdyke et al., Science   By systematically examining Antarctic seabed sediments, Opdyke and colleagues showed that periodic shifts in earth’s magnetic polarity could be used to accurately date sediment layers back beyond 2 million years—and thus climate shifts from those ancient times. Previously, the limit was only 25,000 years. This set the stage to test theories of climate change in deep time.

Wallace Broecker, who joined Lamont 60 years ago, is considered one of the founders of modern climate science. He has made some of the most important discoveries about oceanography and climate, and continues his work today.

1973: Are we on the brink of a pronounced global warming? Wallace Broecker, Science   This is the paper generally credited with coining the phrase “global warming” in scientific literature. The planet at that time was emerging from a decades-long natural cooling cycle, which Broecker postulated had been masking an ongoing warming effect caused by rising industrial carbon-dioxide emissions. Broecker predicted that as the cooling cycle bottomed out, global temperatures would rise swiftly. He was right.

1976: The surface of the ice-age Earth CLIMAP, Science   CLIMAP, an international project in the 1970s-80s, reconstructed the world’s sea-surface temperatures, and thus overall climate, during the last glaciation. The main evidence was deep-sea cores—many taken by Lamont scientists and held in the Lamont Deep-Sea Core Repository, the world’s largest. It was the first comprehensive look at earth’s temperature for a time markedly different from our own.

1976: Variations in earth’s orbit—pacemaker of ice ages James Hays, John Imbrie, Nicholas Shackleton,  Science   In the 1920s, Serb mathematician Milutin Milankovic proposed that earth’s ice ages coincide with cyclic changes in the eccentricity, axis orientation and wobble of the earth as it orbits the sun. The idea was long debated. This paper finally proved to most scientists’ satisfaction that Milankovic cycles are real. Lamont’s James Hays worked with two other giants of modern science: Brown University’s John Imbrie and Cambridge’s Nicholas Shackleton.

1978: The Marine oxygen isotope record in Pleistocene coral, Barbados, West Indies Richard G. Fairbanks et al., Quaternary Research   This paper documented the magnitude and rapidity of sea-level rises when ice sheets and glaciers melted at the ends of several previous ice ages. Other Lamont researchers have followed with many more studies to the present quantifying past changes in sea level. These studies are key to understanding how current melting of ice may affect us in the near future.

1986:  Experimental Forecasts of El Niño Mark Cane, Stephen Zebiak et al., Nature   El Niño is earth’s most powerful natural climate cycle, shifting precipitation and temperature patterns, to affect crops, disease outbreaks and natural hazards globally. Its physics and variable timing were long cloaked in mystery. Cane and Zebiak were the first to construct a model that explained how it worked, and could successfully predict an El Niño. This and related work led to forecasts that are now used worldwide to plan for crop planting, public-health initiatives and emergency relief efforts.

1986: Inter-Ocean Exchange of Thermocline Water Arnold Gordon, Journal of Geophysical Research In conjunction with earlier oceanographic work, laid out how differences in the temperature and salt levels in different layers drive the exchange of water between oceans, and, ultimately, affect climate over vast distances.  Gordon and colleagues continue to work on questions of large-scale ocean circulation in Indonesia, the Southern Ocean and elsewhere.

1989: The role of ocean-atmosphere reorganizations in glacial cycles Wallace Broecker and George Denton, Geochimica Cosmochimica Acta   This study explored the role of freshwater inflow into the northern North Atlantic, via melting ice, in governing the oceanic “conveyor belt,” and its possible association with disruptions of currents that could cause sudden, large-scale climate changes. Followed by many other papers including 1992’s Evidence for Massive Discharges of Icebergs into the North Atlantic Ocean During the Last Glacial Period (Gerard Bond et al., Nature).

With glaciers now melting worldwide, understanding their dynamics past and present is key to projecting the future. Lamont scientists study ice trends all over the world. Here, a researcher on an expedition to core the waning glacier atop Indonesia’s Puncak Jaya, earth’s highest peak between the Andes and the Himalayas.

1995: Temperature histories from tree rings and corals Edward Cook, Climate Dynamics Cook, now head of Lamont’s Tree Ring Lab, showed how tree rings dating back as far as 1,000 years correlated with both modern instrumental records and marine corals to show anomalous warming during the 20th century in many parts of the world. Working from places ranging from Tasmania and South America to Mongolia, North America and Scandinavia, lab scientists have since published many more papers on how tree rings illuminate regional and global climate histories. These include a monumental drought atlas of Asia, published in 2010.

1995: Plio-Pleistocene African climate Peter de Menocal, Science This connected the evolution of humans with a shift toward more arid conditions in the east African climate after 2.8 million years ago. The change resulted in the development of open savannahs where newly upright human hunters are thought to have thrived. It was one of the early papers suggesting climate’s basic effects upon humans. Many uncertainties persist about early human evolution, but many scientists continue investigations of the evolution-climate link.

2000: Climate change and the collapse of the Akkadian Empire: evidence from the deep-sea Heidi Cullen, Peter de Menocal et al. Geology   The sophisticated Akkadians ruled the Middle East  until 4,200 years ago, when their empire suddenly collapsed. Heidi Cullen (who later became a popular TV personality covering climate) linked it with an abrupt 300-year drought, using layers of dust found in seabed deposits. This helped nourish the emerging awareness of how environmental change may affect societies. Later related Lamont papers include a 2010 study exploring the collapse of southeast Asia’s Angkor culture, and other Asian societies, also apparently due to drought.

2002: Global sea-air CO2 flux based on climatological surface ocean pCO2, and seasonal biological and temperature effects Taro Takahashi  et al., Deep-Sea Research Part II   Based on some 940,000 measurements taken over four decades, Taro Takahashi and colleagues mapped for the first time on a global scale the exchange of carbon dioxide between the atmosphere and oceans—a flux that plays a key role regulating climate. This was followed by papers including 2009’s Reconstruction of the history of anthropogenic CO2 concentrations in the ocean (Samar Khatiwala et al., Nature), which indicated that since 2000, the world’s oceans may have begun losing their ability to absorb rising human emissions of carbon.

2004: Long-Term Aridity Changes in the Western United States Edward Cook et al., Science   Tree rings showed that an ongoing drought in the U.S. Southwest paled in comparison to one during an unusually warm period about 1,000 years ago. It suggested that the region is vulnerable to disastrous drying due to global warming. An influential 2007 paper followed, led by climate modeler Richard Seager: Model Projections of an imminent transition to a more arid climate in southwestern North America,” Science.  This added evidence that the region will dry significantly in the 21st century–a transition now probably already underway.

2008: In Situ Carbonation of Peridotite for CO2 Storage Peter Kelemen, Juerg Matter, Proceedings of the National Academy of Sciences   With the recognition of the problems caused by rising carbon dioxide, Lamont scientists in several disciplines have been among the first to look into possible ways to capture and store emissions. This paper documents efforts to use natural chemical reactions within deep-earth rocks in Oman to “freeze” emissions into underground reservoirs. Projects by other researchers are looking into piping emissions into the seabed off the U.S. Northeast, or using rocks common on the U.S. mainland.

Tree rings contain exquisitely detailed records about past climates. Members of the Tree Ring Lab travel to many remote places to collect and study samples. Here, researchers work at the edge of the northern Alaska tundra.

2011: Civil conflicts are associated with the global climate Solomon Hsiang et al., Nature   In the first study of its kind, Hsiang and his colleagues linked periodic increases in civil conflicts to the arrival of El Niño. The study found that the characteristic hotter, often dryer weather in certain areas doubled the risk of warfare across some 90 tropical countries, and accounted for a fifth of worldwide conflicts in the past 50 years. There is now speculation (though no proof) from studies done at Lamont and elsewhere that El Niño cycles themselves could be intensified by rising global temperatures in the future.

2012: The geological record of ocean acidification Bärbel Hönisch et al., Science Lead author Bärbel Hönisch and her colleagues showed that the world’s oceans are turning acidic at a rate unprecedented over at least the last 300 million years, apparently due to reactions with human emissions of CO2. This could affect marine ecosystems, and may already be having effects in regions such as the U.S. Pacific Northwest.

2015: Climate Change in the Fertile Crescent and implications of the recent Syrian drought  Colin P. Kelley et al., Proceedings of the National Academy of Sciences   This study asserts that a record 2006-2010 drought in Syria was stoked by climate change–and that the drought in turn helped propel Syria and surrounding nations into the vast war that has evolved into one of the worst disasters of modern times.  It made worldwide headlines, and has become one of the most highly cited pieces of research linking ongoing climate trends with drastic consequences for humanity.

2015: Contribution of anthropogenic warming to California drought during 2012-2014  A. Park Williams et al., Geophysical Research Letters   With record-breaking drought devastating California starting in 2012, many scientists began looking at whether global warming was playing a role. Bioclimatologist A. Park Williams and his colleagues showed that while natural factors probably caused the lack of rainfall, global warming played a measurable role in the drought by drying out soils further. The study was instantly seized by politicians and others as hard evidence that climate change is already affecting agriculture, economy and environment in the United States.

RELATED VIDEO: THE LAMONT DEEP-SEA CORE REPOSITORY’S CONTINUING ROLE IN CLIMATE STUDIES

Click here to view the embedded video.

 

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Women Making Waves

Future El Niño - Mon, 06/11/2012 - 11:55

By Allison Jacobel

In the seafaring lore of yore at least two statements have traditionally been held as fact: the more rum the more merry the mates and any and all women are bad luck. While the origin of the first statement is fairly obvious, the second may require a bit of explanation. In the times of ancient mariners it was held that not only were women incapable of doing physical work aboard a ship but also that they were a distraction to the men onboard.  Together these two factors were thought to produce a dangerous inattention to the sea which could anger the forces of nature and cause fearful storms and gales.

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Samantha Bova (Brown University) prepares to deploy and XBT over the side of the R/V Langseth. XBTs are used to measure the temperature and salinity of the ocean.

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The female geoscientists aboard the Langseth.

Jean Lynch-Stieglitz in a teaching moment in front of the main lab console.

Christina King, Ashley Maloney, Allison Jacobel and Kate Wejnert getting ready to sample the CTD.

Fortunately (or perhaps unfortunately depending on how you feel about the first statement), we here on the Marcus G. Langseth are bucking the shackles of yore in the most dramatic of fashions.  On this cruise not only do we have women aboard but all ten of the graduate students and our post-doc are female[1]!

Aboard the Langseth are:

Sam Bova – Brown U., Ann Dunlea – Boston U., Heather Ford- U. of California, Jen Hertzberg- Texas A&M, Allison Jacobel – Columbia U., Christina King – U. of Rhode Island. Ashley Maloney – U. of Washington, Julia Shackford- Texas A&M, Kate Wejnert– Georgia Tech, Ruifeng Xie – Texas A&M.

While over the past 20 years, women have increasingly demonstrated their ability to compete in many sectors of the workforce, a slower trend has been observed in the geosciences than in any other STEM discipline except engineering. In 2004, 42% of the BA and BS degrees awarded in the geosciences were to women and only 34% of the PhDs awarded in the geosciences were to women[2].  Most troubling is that of full professors in US geosciences departments only 8% are women[2].

It will likely take more than one generation to overcome these trends, but many of us aboard the Langseth are optimistic.  While the driving forces and support networks behind the women on board are unique, several commonalities can be found.

I think most in the field would agree when I say we’re a well-awarded group and here I think credit is due to both government programs and private foundations for recognizing the need and opportunity to support young women in science.  While some might point to the demographics on board as a reason that the emphasis on supporting women in science is no longer needed, I think the scarcity of female professors in tenured positions at most universities is a clear argument that this emphasis should continue.

We also owe thanks to the pioneering female scientists who were instrumental in deconstructing many of the biases against women in science and who paved the way for our generation’s steps forward. For example we are fortunate enough to be led in our scientific mission by Jean Lynch-Stieglitz, one of our two chief scientists.  Jean was the first female professor in the Department of Earth and Environmental Sciences at Columbia University and holds amongst many accomplishments the 2000 receipt of a NSF CAREER Award in recognition of her role as an outstanding leader in both education and research.  Jean is currently a professor at Georgia Tech and last but certainly not least, mother of two.

Finally, I think some credit is due to the male scientists on board (and those PI’s back on land) who helped to bring us each aboard and who recognized our skills, drive and potential among a field of qualified candidates.  These men are neither intimidated by, nor resentful towards, the smart women aboard and have invested their time and academic resources into helping us all to become better scientists.

While the prevalence and acceptance of women in the geosciences is growing, we are also aware of the professional gaps left to be bridged, both in our own field and others.  I don’t take the opportunities I’ve been given for granted and believe I speak for the other women aboard when I say we hope to encourage other young women to pursue their interests in the sciences and other traditionally male-dominated fields. Through participation in professional societies, activities involving disadvantaged girls in schools, summer programs and more, we hope to make waves not only in the seas of the South Pacific but also in in the communities we call home.

For more information about women in the geosciences check out the NSF/AWG sponsored workshop proceeding “Where are the Women Geoscience Professors?”

Allison Jacobel is a graduate student at Columbia University who studies the past circulation of the ocean and atmosphere using the chemistry of deep ocean sediments.

[1] I should not neglect to mention that we are fortunate to have one male undergraduate on board, Victor Castro, who is a much-appreciated member of the scientific party.

[2] Holmes, M.A., O’Connell, S., Frey, C. & Ongley, L. Gender imbalance in US geoscience academia. Nature Geoscience 1, 148–148 (2008).

Transitions: Climate, Fire, and Forests in Mongolia

The silence you may have heard since our last post was the sound of microscope lights flickering, measuring stages gliding, brains grinding, numbers crunching, and poi dogs pondering. We wrapped up all planned field work last summer for our research grant on climate, fire, and forest history in Mongolia. We have transitioned from the field-intensive portion of the grant to the data and publication phase of the scientific process. We have presented research in various meetings and settings and have earnestly begun to put our findings to our peers to begin the publication process. We are also transitioning to a new vein of research in Mongolia that gets to the title of this blog. It has been a long time coming.

First, Dr. Amy Hessl was inspired by the forest in transition on Solongotyin Davaa. This is the famous forest where global warming was first reported in Mongolia. High elevation forests are rare to burn. So, the thought that a landscape with wood that has been on the forest floor for more than 100o years became an important part of Amy’s summary on “Pathways for climate change effects on fire: Models, data, and uncertainties“.

The 2010, post-fire landscape of Solongotyin Davaa from Figure 1 in Hessl’s “Pathways for climate change effects on fire: Models, data, and uncertainties”

Next, Amy led a slew of us in a publication summarizing our initial findings of fire history from the northern edge of the Gobi Steppe to Mongolia’s border with Russia near Sükhbaatar City. With the glaring exception on Bogd Uul, this paper, “Reconstructing fire history in central Mongolia from tree-rings“, gives a quick glimpse into the fairly persistent fire regime across central Mongolia over the last 280-450 years.

Four centuries of fire history in central Mongolia: initial results

NPR recently finished a series of reports on the environmental and cultural transitions currently happening in Mongolia as a result of climate change and the massive mining boom underway. The post that caught our attention was the one on “Mongolia’s Dilemma: Who Gets The Water?” Water has been a focus or the Mongolian-American Tree-Ring Project (MATRIP) since the beginning (see MATRIP’s major publications on this subject here, here (get the streamflow data here), here, here). So, we are happy to announce that this rich vein of research has continued with the fire history research grant by first filling an important gap in the MATRIP network and then having several manuscripts on this subject in revision or review.

One paper that we are quite excited about is an analysis of drought variability across Mongolia’s ‘Breadbasket’. We were taken aback in throughout the last three field seasons by the large-scale revitalization of Mongolia’s agricultural sector. It was surprising to see center-pivot irrigation and large tracts of fields in northern Mongolia. This cultural change is intended to transition Mongolia towards agricultural independence for its growing population. Our analysis highlights important differences in drought variation for the eastern and western portions of the breadbasket region. Stay tuned!

Finally, we are headed back to Mongolia this summer to begin pilot work on new research currently funded by the Lamont Climate Center, The National Geographic Society, and West Virginia University. As hinted in our last post, we will begin field work to determine if there was a warmer and wetter climate during the rise of Chinggis Khaan’s Mongol Empire.

Really –  stay tuned!


Categories: TRL

Under Arctic Ice: Watch the Video

Click here to view the embedded video.

This video depicts the activities of the LDEO Switchyard field team, which deploys annually and uses ski-equipped aircraft to reach a series of sample sites between the North Pole and Ellesmere Island in Canada.

After landing, a hole is drilled through the ice, and the sampling system is lowered through the hole to a depth of about 700 meters. The sampling system (the thin hole rosette) which was designed and built at the Lamont-Doherty Instrument Lab, allows the LDEO field team to examine the water as the assembly descends and to collect water samples for later analysis when interesting properties are observed. This work is supported by the US National Science Foundation.

This video was shot by Switchyard team member Dan Greenspan, who is a researcher at the Applied Physics Laboratory at Johns Hopkins University. Check out his blog, and his recent entry: “Traveling to the North Pole, Part 10: Eclipse, with Wolves.”

The End of the Line

Sea Ice Blooms in the Far North - Tue, 05/22/2012 - 11:27
The R/V Oscar Dyson pulled into Dutch Harbor, Alaska on May 9 after a hectic few final days! We are now starting to sift through the hundreds of samples and a hard-drive worth of data we shipped back, unpacking our eleven boxes of gear, and re-packing perhaps even more for an upcoming cruise off the coast of Brazil. Thanks to everyone who helped make our cruise aboard the R/V Oscar Dyson such a success!

Final Days in Alert

Time is flying, bringing us to our final days in Alert. We were able to recover samples from 12 stations, which is a great success and the second most successful year on record. Thanks to everyone who made it happen: Dale, Richard and Dan who went out every possible day to collect samples; Al and Jim for their support in Alert and of course our friendly Canadian colleagues..

The next two days are filled with packing and arranging the equipment and samples for their long journey home to New York. We plan to fly out of Alert on May 22 to Kangerlussuaq, Greenland but don’t know yet when the Air National Guard will pick us for the flight to New York. We hope to be home by May 25.

Locations of the 12 stations where we collected samples this season.

Lucky 13 Gets Us 250,000 Years of Sediment

Future El Niño - Sat, 05/19/2012 - 22:41

Beautiful white sediment inside the core barrel.

mud tatto

A mother’s day tattoo celebrates the good cores we are getting.

sediment cores

Rick Murray (Boston University), Victor Castro (University of California, Santa Cruz) and Samantha Bova (Brown University) discuss what the sediment’s color tells us about ocean chemistry

We have been steaming and searching for locations on the seafloor where the sediments are accumulating undisturbed. We tried without luck to take cores at several promising locations, however the cores came up less than perfect.  It turns out that much of the undersea portion of the Line Islands has ocean currents that remove and erode sediment. This erosion shows up in the sediment cores as sandy layers where the very small grains of sediment have been swept away. So, we kept up our vigil in the main lab area, closely monitoring the seafloor for small pockets of sediment that looked promising. Some pockets are only a few tenths of a mile across while others are a mile or two. Many that look beautiful from a distance turn out to be ugly on closer inspection.

On our 13th core attempt of the cruise, we got lucky. The corer came back full of the beautiful, white mud. The 20-foot core contains over 250,000 years of sediment and spans the last three glacial cycles in earth’s history. During each of these cycles the earth cooled and large ice sheets expanded over North America and elsewhere. In our core, these cycles are indicated by color changes from greenish brown to white and back.

After lucky 13, we began to hone our strategy and are finding more locations with good sediments. We now have lucky 15, 17, and many more; we now have over 30 cores and counting. Not all of them are perfect, but we are getting better at finding good sediments and faster at coring them.

sediment analysis with multi-sensor track

Ann Dunlea (Boston University) uses a multi-sensor track to analyze a sediment core aboard the R/V Langseth.

sniffing sediment for hydrogen sulfide gas

Mitch Lyle (Texas A&M University) sniffs a new sediment core for whiffs of hydrogen sulfide gas. Decomposition of dead algae in the sediments helps produce the gas.

tropical sunset

A beautiful tropical sunset provides an excuse to relax.

A Walk against Cancer

Alert hosted the first northernmost cancer-fighting fundraising event “Relay for Life,” an event sponsored by the Canadian Cancer Society to celebrate cancer survivors, remember loved ones lost to cancer and fight back against all cancers.

Lights to honor loved ones.

The 12-hour-walk was organized by Kristy Doyle, who lost her grandfather to cancer in 2010. Participants raised a whopping $7,580 and collectively walked 900 kilometers. I admit that I feel proud for doing my small part by walking 8 kilometers.

More than 900 kilometers walked in 12-hours

A Rare Treat – The Green Flash

Future El Niño - Tue, 05/15/2012 - 16:00

By Lee Dortzbach,

light dispersion through a prism

Refraction through a prism separates light into different colors. The atmosphere has the same effect, separating the sun’s image into the ROYGBIV colors (red, orange, yellow, blue, green, indigo, violet). The sun’s green image is visible during the sunset when the brighter orange and yellow images fall below the horizon. Image courtesy of D-Kuru/Wikimedia Commons licensed under the Creative Commons Attribution-Share Alike 3.0 Austria.

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Enlarged view showing the green at the edge of the sun’s disc. Photo by Tatiana Moreno, a protected species observer on our cruise.

I work as the Chief Mate aboard the Research Vessel Marcus G. Langseth for this cruise and stand the 4 to 8 watch.  Every morning as I get the ship where the scientists need to be, I watch for the sun to rise.  Every evening I watch for it to set.  There are some days when clouds are around and make for some great sunsets.  Other days we cannot see the sun through all the clouds.

Sunday night after successfully recovering a gravity core about 42 miles north of the equator, conditions were right for a rare treat – the green flash.  There were clear skies around the Sun, good visibility and a clear horizon.  When I first heard about the green flash, I thought it was something that was noticeable and quick.  Over the last decade, I have seen that it is not a sky-covering flash (as depicted in the recent Pirates of the Caribbean: At World’s End), but a short lived change of the sun’s light as it sets.

It happens because of refraction of light through the Earth’s atmosphere.  The white light of the sun is broken into different wavelengths of visible light we recognize as different colors.  The red and orange cover most of the sky, the yellow of the sun gets more orange-like as the sun sets and the blue and violet get scattered too much for us to see.

So what about the green?  It too is scattered most of the time until the tip of the Sun is barely visible above the horizon.  The Sun’s yellow light is refracted more and so the ‘yellow’ sun sets below the horizon before the ‘green’ sun.  The sliver of green becomes visible to our eyes only when the bright yellow light is fading during the sunset.  It starts from the bottom up in a horizontal band that grows a little taller as the sun sets.  On a few occasions I have seen a sliver of blue/violet light below the green (a challenge against a blue ocean and a greater treat).  In the latitude of the United States, it lasts about 0.7 seconds.  Sometimes it can last up to 4 seconds.  Ours lasted between 1 and 2 seconds.  Definitely a flash compared to the core we just recovered!

For more information and other pictures of green flashes, click here.

Lee Dortzbach graduated from the U.S. Merchant Marine Academy with a B.S. in Marine Transportation in 2000. He has been around the world on several different ships over the last decade, including two oceanographic research vessels. He lives in landlocked Utah.

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Beginning of Sunday’s green flash. Photo by Tatiana Moreno.

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More green visible as the sun sets. Photo by Tatiana Moreno.

A Visit to Crystal Mountain

The weather has improved considerably and we were able to fly out today to collect more samples. Yesterday, some of us went to explore Crystal Mountain, a 900-foot peak about five miles from Alert that offers an excellent view of the surrounding landscape.

Crystal Mountain at the left.

Ronny Friedrich on Crystal Mountain.

Alert is a Canadian military station located in the far north region of Qikiqtaaluk, Nunavut, Canada–the self-proclaimed “northernmost permanently inhabited place in the world.” There is no doubt that Alert is unique, with its 10-months of snow cover, extremely harsh winters with temperatures as low as -40 degrees C (-40 F) and average summer temperatures hardly above freezing. Alert is named after the HMS Alert, a British ship that spent the winter of 1875-1876 about 10 kilometers east of present-day Alert while exploring the arctic. The HMS Alert was the first ship to get that far north. Alert was settled as a weather station in the early 1950s and at the height of the Cold War became a military base due to its proximity to what was then the Soviet Union.

View toward Alert and the Arctic Ocean. Alert is the darker spots to the left.

Alert is a fascinating place that has seen more than its share of downed airplanes and where the hardships that earlier inhabitants endured are still apparent. Nowadays, life is easier and does not evoke the romantic images of arctic exploration of the past. Sure, the Internet moves at a snail’s pace and telephone-use is restricted to 30 minutes per day, but the food is excellent, and we are warm and dry.

Ice cores…finally

Today I got another chance to go out with team CASIMBO to drill ice-cores. The weather was beautiful with no wind, a few clouds, bright sunshine and a balmy temperature of about 5 degrees F.

The smooth snow and ice in the foreground is the Arctic Ocean "beach" while the rubble in the back is actual sea ice.

When I first saw sea ice near Alert a few years ago, I was very surprised. It wasn’t anything like I had imagined. One might expect sea ice to be like lake ice: smooth and flat. But Arctic Ocean ice is in constant motion, driven by winds and ocean currents. Big chunks of ice break-up, smash into each other and create ice that looks more like a rubble field.

Trying to find a way through the ice field to the sampling location.

As we drove over the icy rubble on our snowmobile, we searched for a route to our sampling location, about 3 to 4 miles away from Alert (45 minutes by snowmobile). Taking an ice-core is relatively simple. One of the pictures shows Ben using the corer. It is basically a plastic pipe with cutting knives at the end that drills into the ice while keeping the ice-core trapped inside. After 3 feet of ice is cored, the corer is lifted out of the hole and the ice core is packed into containers for further processing in Alert.

Ben drilling an ice-core

The ice above was about six feet thick but generally, thickness varies. There is thin ice that has just formed on open water between ice floes, first year ice, or ice that has formed this winter, several-feet thick and ice that has formed over several years that can be more than 20 feet thick.

Drilling Ancient Mud from Seafloor No Easy Task

Future El Niño - Wed, 05/09/2012 - 23:01
A sediment core is secured along the ship’s rail for sampling.

A sediment core is secured along the ship’s rail for sampling.

Watching winch tension as a core is pulled out of the seafloor.

Scientists monitor how hard the cable is pulling as a sediment core is pulled out of the seafloor. Too much pull will stretch the cable and could cause it to break, leaving the sediment corer on the bottom of the ocean.

Yesterday we left our first study region with new samples from the seafloor and a healthy respect for the ocean currents that can erode sediment deep in the ocean.  The samples will be useful for our research but we had to work for them.  The seafloor we surveyed was heavily eroded and we had to look carefully before finding sites that were promising enough to sample.  Even then we ran into difficulties getting the sediments back to the ship.

We spent several days surveying the seafloor using instruments on the ship to identify possible sites for sampling.  We looked for flat areas where we could see layers of sediment below the seafloor.  These layers show up in the echoes from sound pulses in a type of measurement called seismic reflection (see previous blog post).  Unfortunately much of the region we surveyed has deep gullies with no sediment layers.  Ocean currents have scoured these regions leaving no sediment for us to core.  We finally located several small areas that had a hint of sediments and one big pile of sediment we thought would be our best chance for samples.

We use a sediment corer to take samples of the seafloor.  The corer is a long tube with heavy weights on top that push the tube down into the seafloor.  When the tube is pulled out it removes a long cylinder of sediment that we bring back to the surface.  The corer is lowered on a steel cable at about 1.5 miles per hour and takes more than an hour to reach the seafloor.  At 150 feet above the seafloor, a mechanical trigger releases the corer from the cable and 5,000 pounds of steel rocket towards the bottom.  The weight and speed push the corer up to 30 feet into the sediments.  Then we have to pull the corer back out.  Sometimes this is easy but if the sediments stick to the corer it can take almost 20,000 pounds of pull to free the tube and slide it out.

Section of sediment core

A section of sediment core showing changes from clay sediments at the bottom to sandy sediment on top.

Sorting foraminifera shells

Foraminifera shells a few millimeters across can be sorted with a fine-tipped paintbrush. The different species of foraminifera can be used to determine the age of the sediments.

The other important step in coring is to keep the sediments inside the tube on their two-mile trip back to the surface.  This seems obvious but we ran into troubles with the very first core we took.  Usually a ring of metal fingers in the bottom of the core (called a core catcher) keeps the sediment inside the tube.  However, the sediment we were coring contained a lot of sand-sized shells that was washing out of the tube leaving us with no sediment by the time the corer reached the surface.  To prevent this, we added a sock of fabric around the core catcher to keep the sand from washing out.  Bingo!  The fabric kept the sand in the corer and we started recovering sediments to study.

When the sediment corer arrives at the ocean surface it is laid horizontally along the ship’s rail where we take a sample of the sediment in the core catcher to determine the age of the bottom of the core.  This age is determined by looking for a striking, pink colored shell made by a type of plankton called foraminifera. This pink foraminifera was abundant in the Pacific Ocean until 120,000 years ago, so if we find pink shells we know the sediments are at least 120,000 years old.  We will do more detailed analyses later but this age gives us our first peek at how much time it took for the sediments to accumulate.

Next, we cut the core into smaller sections that are easier to handle and the core is split open so we can see how the sediment looks.  We study its color, texture and composition before storing it in a refrigerated container aboard the ship.  At the end of the cruise we will send the container to the Deep-Sea Core Repository at Lamont-Doherty Earth Observatory where the sediments will be preserved for researchers around the world to study.

We are now steaming south to the equator to start a new survey to find the right locations to drill more sediment cores.

Sock inside the core catcher

Katherine Wejnert from The Georgia Institute of Technology samples the sock inside the core catcher.

Cutting a sediment core into sections.

Steve Hovan (Indiana University of Pennsylvania) and Allison Jacobel (Columbia University) cut a sediment core into sections.

Preparing to take notes on the sediment composition.

Christine King (University of Rhode Island) prepares to take notes about a new sediment core.

Microscopic examination of sediments

Jennifer Hertzberg (Texas A & M University) determines how old the sediments are by looking for a pink-shelled species of foraminifera that lived in the Pacific Ocean 120,000 years ago.

Ice-Coring…Almost

The weather became increasingly cloudy yesterday with low visibility and snow. That means no flying. The forecast for the next 24 hours doesn’t look promising either. As usual in the Arctic it’s better not to forecast — everything might change within hours.

Getting ready to get ice-cores together with colleagues from University of Alberta.

In addition to the standard suite of samples that we usually take, this year we will take ice-core samples to see how the melting sea ice below is affecting the ice. Our colleagues from the team CASIMBO, at the University of Alberta, have shared pictures of their ice-cores with us.

An ice-core under polarized light showing snow cover on top and ice crystals forming below.

To get a feeling for the amount of work necessary to drill an ice-core, I tried to join CASIMBO out on the ice via snowmobile, but due to the bad weather we had to return to the base. The wind and snow was picking up, and clouds prevented us from judging the condition of snow-covered surface we were driving on. (There are no roads here!) The risk of getting lost was far too great. I wore several layers of clothing, including three pairs of heavy socks, but was still shivering in the cold.

Not much to see in bad weather. Total white-out.

Sampling Water at the North Pole

The 2012 field season started out better than we could hope for. The weather has been great for flying and sampling water below the thick sea ice that covers much of the Arctic Ocean. Good weather means no low clouds or fog to prevent our pilots from seeing where they are going. Unlike regular airplanes that can land and take off in most weather, our planes don’t have the fancy technical instruments such as radar that can peer through cloudy skies. We were able to recover water samples from three stations, including one at the North Pole–a big success since the North Pole is crucial to understanding global ocean currents. The North Pole station is the farthest from Alert, requiring four to five hours of flying to get there, including a stop to refuel on the way and sometimes on the way back. To refuel, we land on the ice where we have have prepared a make-shift gas station several days earlier. The station consists of several drums of fuel and a beacon that allows us to find it on a constantly shifting landscape of ice; the sea ice moves several hundred meters each day. Unlike the South Pole, the North Pole is surrounded by water and so the landscape here looks very uniform. It’s hard to know that you’ve arrived some place special.
To collect our water samples, we drill through up to eight feet of ice and lower a special sampling device into the hole that will measure the water’s temperature, salinity (conductivity) and dissolved oxygen as it descends. Today we are not allowed to fly and so we will spend the day resting and preparing our equipment for the days ahead.

On the Move

Sea Ice Blooms in the Far North - Mon, 05/07/2012 - 14:57
After another day spent hiding out in the Aleutian Islands, we are headed northeast towards the sea ice to attempt recovery of two oceanographic moorings. The weather is improved, only a couple of days remain for scientific study, and we are excited to hopefully accomplish one of the main goals of this cruise!

Albany to Alert

Our annual trip to the Arctic starts in Albany, where the Air National Guard will fly us north in a  venerable C130 Hercules military transport plane.

C130 Hercules

Inside the C130. No first class here, not even economy.

First stop is Kangerlussuaq, Greenland, where we will stay overnight. Kangerlussuaq (in Danish: Søndre Strømfjord) is a settlement in western Greenland, home to Greenland’s largest commercial airport. As usual, we were greeted by our friendly colleagues from the Kangerlussuaq Science Support Center (KISS) that supports all science operations in and around Greenland. Temperatures are getting much lower than down south at about 40F (5 degrees C). Kangerlussuaq is home to Greenland’s most diverse land-based wildlife such as musk oxen, caribou, gyrfalcons and the Greenland sled-dog.

Me and the Greenland sled-dog.

Next stop is the U.S. Air Force Base Thule in Northern Greenland, where we refuel and head to Alert. On the way from Kangerlussuaq to Thule we fly along the coast of Greenland, over Baffin Bay, where the Arctic starts to show its icy face. For me, Greenland is fascinating for its mild temperatures, diverse wildlife in the south and breathtaking frozen state in the north. I also like the Danish pastries served in the airport cafeteria – it reminds me of home.

Coast of northern Greenland

Finally, we arrive at the Canadian Forces Station (CFS) Alert around noon. Our home for the next few weeks.

Alert

Through the Looking Glass: Peering Through the Bottom of the Ocean

Future El Niño - Sun, 05/06/2012 - 04:02
Learning about how to take sediment cores.

Scientists aboard the R/V Langseth learn how to prepare sediment core tubes before they are lowered to the bottom of the ocean.

Sunset over the tropical Pacific Ocean. Deep below the waves, large mountains rise up above the seafloor.

Scientists monitor the echoes as they stream into the main lab aboard the R/V Langseth.

We are in the fifth day of our research cruise to the Line Islands and shipboard life is beginning to settle into a routine.  Most people have their ‘sea legs’ and our sleep schedules are adjusting to the midnight to noon or noon to midnight work shifts.  Meals are a time to catch up with scientist and crew, and the motivated scientists have begun regular exercise schedules in the ship’s gym.

As we steam over the incredibly wide expanse of the Pacific Ocean, the waves seem endless and monotonous, and the wind blows steadily from the same direction for days on end.  However, beneath us the seafloor is far from monotonous. Huge mountains rise 10,000 feet above the seafloor and create escarpments, ridges and valleys that would rival the peaks of the Rocky Mountains.  It is along these mountains that we hope to find sediment for our research.

Using scientific instruments we peer ‘through the looking glass’ to learn what the seafloor and sediments look like.  The analogy to the looking glass is apt: Alice stepped through the mirror to see the world beyond and we peer through the bottom of the ocean to see what is below.  However, unlike Alice, we use our ears.  Short pulses of sound from the ship are focused on the seafloor and we listen to the echo and reverberations that return to the ship.  Depending upon the pitch and intensity of the sound we can look at the top layer of the sediment or much deeper.

Sound pulses echo off the seafloor and are detected by our ship. The time it takes the pulses to return tells us how deep the seafloor and sediment layers are below the surface.

The most basic echo we listen to comes from the very top of the sediments.  This echo travels down through ocean, bounces off the top of the sediments and returns back to the ship.  We measure the time it takes to go down and come back up, and knowing how fast sound travels through seawater (~one mile per second or 3,400 miles per hour!) we can determine the distance to the bottom of the ocean.  The times are very short, about two seconds for water a mile deep.  We use these distances to construct a detailed map of the bottom of the ocean.  This map shows the mountains and valleys on the seafloor where we will take our sediment samples.  We also listen to how loud the echo is when it comes back to the ship.  Hard surfaces like rock have a loud echo while soft sediment gives a quiet echo.  This is an additional way to determine where there are ocean sediments to sample.

If we turn up the sound volume and use a lower pitch we can look beyond the seafloor into the sediments below.  Now rather than just one echo from the seafloor, we begin to hear many echos as sound reflects off the different layers in the sediments.  These echos allow us peer beneath the seafloor to know how thick the sediment is and whether it is nicely layered or jumbled and distorted.

When we find the right sediments—not too deep, smooth, with nice layers—we will take cores of the sediment to study the climate history preserved in the layers.

Side-looking map of Kingman Reef (part of the Line Islands) and the surrounding seamounts and valleys (colors indicate the depth of the seafloor, 5000 meters is over three miles). Robert Pockalny, a geophysicist from the University of Rhode Island, constructed this map from depths determined by sound pulses that echo off the sediment.

Calmer Seas Ahead

Sea Ice Blooms in the Far North - Fri, 05/04/2012 - 19:44
After a short break due to weather and a bit of fun with Styrofoam cups, we are back in the lab sampling phytoplankton in the Bering Sea. We are using a specialized instrument to determine how well these small plant-like creatures are able to photosynthesize in the ocean, and we continue to learn fun facts about fish larvae from our colleagues.

Exploring the Bering Sea Ecosystem

Sea Ice Blooms in the Far North - Thu, 05/03/2012 - 03:20
Our stations have continued to be rich in phytoplankton, while our colleagues are excited by the larval fish they are finding in the southern Bering Sea. Wildlife sightings have included whales, dolphin, and the jawless lamprey fish, and we are settling in for potentially bumpy seas ahead.

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