Glacial burial and decomposition of ancient organic carbon: a scientific expedition to King George Island, Antarctica

July 27, 2010  |   Research Library   |   admin  |   0 Comment
Glacial burial and decomposition of ancient organic carbon: a scientific expedition to King George Island, Antarctica

Prepared by

Ning Zeng (Project Scientist), Associate Professor, University of Maryland, College Park
Jay Gregg, Junior Scientist, University of Maryland, College Park
Email contact: zeng@atmos.umd.edu

Abstract

An expedition to King George Island (KGI), Antarctica was conducted during January, 2010. The main goal was to search for ancient organic carbon buried under ice and to understand the role of such organic carbon in glacial-interglacial CO2 and climate changes. Three trips were taken to study the periglacial environment of the Collins Glacier (Bellingshausen Dome) on the southern edge of the KGI icecap. A glacial moraine was found to contain a large quantity of organic carbon. An outcrop was found to contain several clearly distinguishable layers: rubble, soil, moss, soil, shell, moss, muddy soil, and ice. The surrounding area and the glacial outwash downstream contain large amounts of organic material. CO2 fluxes were measured at two locations using a LICOR-8100 soil CO2 analyzer, with soil CO2 fluxes ranging 15-20ppmv/30min (0.15 mmol m-2 sec-1). Because there was no observable new vegetation growth on the site, and because the chamber where the flux was measured was dark (preventing photosynthesis), it appears that the CO2 was the result of the decomposition of the organic carbon that was once buried under ice. Our findings support the hypothesis that organic carbon, including both vegetation and soil carbon, can be buried under ice, and later released back into the atmosphere, thus contributing to climate change through the emission of CO2, a greenhouse gas. The age of the ancient carbon and the processes and circumstances under which they were buried are yet to be determined.

The expedition was part of a summer school organized in conjunction with the International Polar Year (IPY) 2007-2010.  The IPY is a international effort to foster collaborative research in the polar regions of the Earth.  The first IPY was from 1882-1883, the second from 1932-1933.  This research comes at the tail end of the third IPY, the goal of which was to increase our knowledge of the poles, how they are changing, and to better understand the influence of the poles on the global climate system and vice-versa.  The third IPY marks the largest international collaborative science effort since the International Geophysical Year 50 years prior.

King George Island (KGI)

Research for this project was conducted on King George Island, situated at the tip of the Antarctic Peninsula.  King George Island is the largest of the South Shetland Islands, close to the Antarctic circle at approximately 62° S.  At the north shore is the Drake Passage and to the South is Bransfield Strait. The island is approximately 95 km in length and 25 km across, and has an area of over 1100 square kilometers, of which over 90% is permanently glaciated.

King George Island is a dynamic place.  As the climate has warmed, glaciers are receding from Fildes peninsula on the south-west part of the island.  The newly exposed soil supports lichens, mosses, grasses and other vegetation, as well as Antarctic Terns and Skua.  Coastal areas support Chinstrap and Gentoo penguins, Elephant, Weddell and Leopard seals, Snow Petrels and Kelp Gulls.

Because of the wildlife and the dynamic geology, many countries have established research stations (most of them operating year-round) on King George Island, including Argentina, Brazil, Chile, China, Ecuador, South Korea, Peru, Poland, Russia, and Uruguay.  Research for this project was conducted from the Russian Bellingshausen station, though the field sites were near the edge of the Collins glacier near the glacial moraine.

Trip to/from and around KGI

Getting to Antarctica is not easy.  Some tourists manage the journey on expensive cruise ships, visiting much of the continent, but only coming ashore for short (hourly) stays. Other tourists charter flights, however, again the time spent in Antarctica is short.  Because Antarctica is reserved for scientific research, scientists may arrange longer stays with the invitation of a research station.  The Russian Bellingshausen station hosted more than a dozen researchers and scientists as part of the 2010 King George Island Summer Institute. We booked passage on a Uruguayan Air Force Hercules transport plane. Because of the short runway and treacherous conditions, the flights only occur when the weather on King George Island is fair, with no low clouds. This is by nature hard to predict, as King George Island’s maritime climate can produce quickly changing and unpredictable weather conditions.  For instance, our inbound flight experienced a number of delays, and our return flight was canceled altogether.  Flexibility is a necessity when conducting field research in such an environment.

We spent the first three days on the island conducting reconnaissance hikes with experienced scientists and orienting ourselves with the environment.  We learned the safety protocols when doing field research, the hazards of the island (snow swamps,  slippery permafrost under a layer of mud, and its unpredictable and quickly changing weather. We also learned about the various wildlife on the island, safe distances to maintain, and sensitivity to the fragile flora in this environment.  On these hikes, we discovered areas of particular interest in recently exposed glacial moraines at the edge of the Collins glacier.  It is these areas that served as our field sites for this project.

Environment of Fildes Peninsula, the ice-free corner of King George Island

Climate and Ice

Collins glacier and Bellingshausen dome in background. Moraine is in front of the glacier and a Nunatuk appears on the left side of dome.

For three days, scouting hikes were conducted along the edge of Bellingshausen Dome (Collins Glacier), guided by Russian glaciologist Bulat Mavlyudov. The edge is marked with glacial moraines and nunataks (rock islands in ice).

Over the last several decades, the edge of the ice cap has been retreating rapidly. A moraine about 50 meters away

from the edge of the ice cap was under ice 20 years ago. This is consistent with the general warming in the region. The Antarctic Peninsula is one of the fastest warming regions in the world. The temperature measured at the Russian Bellingshausen Station shows an annual increase of 1.3° C increase in winter temperature over the last 50 years, while the winter temperature has increased by about 2.4° C. Further back in time, the entirety of  King George Island, including the Fildes Peninsula, was covered by ice during the last glacial maximum (LGM) 21,000 years ago when New York was under the Laurentide Ice Sheet.

Bellingshausen temperature record (Saunter, et. al, 2000, Geophysical Research Letters).

Bellingshausen temperature record (Saunter, et. al, 2000, Geophysical Research Letters).

Vegetation

Moss vegetation near the coast of the King George Island

As the ice retreats, vegetation develops quickly on newly exposed land. Lichen, moss and grass grow on KGI. A transect perpendicular to the ice edge was made. Visual inspection showed no visible sign of vegetation in the few meters nearest to the ice edge. This is supported by a team from the University of Wisconsin, led by Professor Les Werner, which measured the photosynthesis and respiration along the edge of the Collins glacier.

Sampling of organic carbon and CO2 measurement

At one location north of Uruguay’s Artigas Station (62°11′04 S 58° 54” W), a glacial moraine was found to contain large amounts of organic carbon. An outcrop that was cut out contained several clearly distinguishable layers: rubble, soil, moss, soil, shell, moss, muddy soil, and ice. Samples were taken from the moss layers. This area is called Site 1. In front of the outcrop is a muddy field of glacial outwash originating from the layered material. A stream winds around the moraine and flows down towards the sea, which was approximately 50m away. Slightly before the stream enters the sea, a mud field appeared to contain the same organic material that was washed out from the moraine and deposited there. Clumps of moss were found in the river-cut deposit and samples were collected at 1 meter and 2 meter depths (Site 2).

Jay Gregg set up the LICOR LI-8100 Automated Soil CO2 Flux System near Site 1.

A pile of moss layer (brown) exposed. Organic odor was clear.

Layered moraine outcrop: moss layers are brown, one layer above the spoon, one layer below. Shells (small white pieces) are below the lower moss layer. Exposed ice (permafrost) is white-blue at the lowest level.

The moraine outcrop from distance; note the spoon as in the above picture.

Glacial outwash deposit, 50m downstream from the outcrop. Organic rich material including dead moss was present inside the deposit.

Results: CO2 measurement

CO2 flux measurements were conducted using the LI-8100 Automated Soil CO2 Flux System at Site 1. Two measurements, both immediately in front of the layered outcrop were conducted: one test spot had visible (dead) moss lumps on the surface, while the other had no visible moss. Tests showed discernable CO2 flux after the standard 3 minute collection time. The collection time was then increased to 30 min afterwards.

Data from the LI-8100 Automated Soil CO2 Flux System were analyzed with LICOR File Viewer software, and further analyzed in Microsoft Excel. To calibrate the instrument to the background level of atmospheric CO2 concentration (388.6 ppmv), data from the CO2 monitoring station on the King Seong Station (South Korea) were used to offset the data recorded by the LI-8100 Automated Soil CO2 Flux System.  This makes no difference on the flux calculations, but is done only to accurately represent the CO2 concentration in the chamber at any given point in the observation trial. The first three minutes of the 30-minute readings were not used in the analysis to allow for the chamber concentration to stabilize once the chamber was sealed.

Site 1, Spot 1, CO2 concentration in the chamber increased by 0.47 ppmv min-1, corresponding to a CO2 flux of 0.09 mmol m-2 sec-1.

Site 1, Spot 2, CO2 concentration in the chamber increased by 0.68 ppmv min-1, corresponding to a soil respiration CO2 flux of 0.15 mmol m-2 sec-1.

Conclusions

Large amounts of organic carbon in a glacial moraine outcrop and the downstream outwash were found at the front edge of Collins Glacier, King George Island. The organic carbon was deposited in the past as layers of moss, interlaced with shells and soil. This suggests that the area was once at sea level when shells were deposited. There were multiple periods of moss development and sedimentation.

The measured CO2 flux was significant, indicating the comparatively rapid decomposition once the old carbon is exposed. There was no evidence of new vegetation growth around the outcrop where measurement was done. This indicates a relatively fresh exposure, possibly within last few seasons.  These results are intriguing, suggesting that soil organisms (decomposers) are active within newly exposed soil from the glacial moraine. Whether they lie dormant under the ice for millennia, or they are newly transported to the area from somewhere else will be determined by carbon dating the soil.  Further work will be undertaken to date the sample to understand the age and developmental history of the organic carbon.

Acknowledgements

We are most grateful to the financial support of the Wilderness Research Foundation, New York, and  its president Sheldon Bart, without whose persistent effort, this work would not have been possible.

References

Hall, B. L., 2007: Late-Holocene advance of the Collins Ice Cap, King George Island, South Shetland Islands. The Holocene, 17, 1253, DOI: 10.1177/0959683607085132.

Zeng, N., 2003: Glacial-Interglacial Atmospheric CO2 Change–The Glacial Burial Hypothesis. Adv. Atmos. Sci., 20, 677-693. Abstract, [pdf]; Homepage of AAS

Zeng, N., 2007: Quasi-100ky glacial-interglacial cycles triggered by subglacial burial carbon release. Climate of the Past, 135-153. [pdf]









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