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NSF & Congress

The Role of Antarctica in Global Change

Dr. Borg

Dr. Scott Borg
Section Head
Antarctic Sciences Section
Office of Polar Programs
National Science Foundation

Before the Senate Commerce, Science & Transportation Committee
November 16, 2004

Thank you, Senator McCain, and members of the Committee, for this opportunity to speak about climate change research supported by the National Science Foundation in Antarctica. While my testimony is focused on the Antarctic I should note that NSF also has a vigorous Arctic research program in climate change called SEARCH - Study of Environmental Arctic Change.

I am Dr. Scott Borg, by training a geologist and currently the Head of the Antarctic Sciences Section at the National Science Foundation. The Foundation has been designated as the lead federal agency to represent US national interests in Antarctica. My group at NSF is responsible for selecting, based on the Agency's merit review system, the research projects that are performed in the United States Antarctic Program (USAP).

While NSF supports the bulk of US Antarctic research there are also important partnerships in climate change research with other agencies such as NASA, NOAA, and the USGS. Facilitating research partnerships between university based researchers and scientists from other federal agencies is particularly important because of the need to achieve an interdisciplinary understanding of Antarctica as an integral part of a global system.

Because Antarctica is at the bottom of the world and mostly uninhabited, we easily overlook how big it is. The continent is larger than the United States and Mexico combined. Two huge ice sheets cover almost all of it, and they average more than a mile thick. These ice sheets contain 90 percent of the world's ice, enough to raise sea level by over 60 meters if they were to melt. The other 10 percent is in the glaciers of Greenland and in mountainous parts of the world.

Antarctica is by far the world's largest region of cold, and its cold and ice have consequences for the world's climate. In geological deep time, before about 35 million years ago, Antarctica was not glaciated. Global average temperatures were 3-4 degrees C warmer than todayi, atmospheric carbon dioxide was higher by a factor of two compared to todayii and there were no polar ice sheets. Geologists call these conditions a greenhouse world. Beginning about 35 million years ago, the world began to cool, the circum-Antarctic current became fully developed and ice sheets formed on Antarctica. Geologists describe this as a transition to an icehouse world that we live in today. Over the last 400 thousand years, the world has oscillated between glacial conditions such as the last ice age, and slightly warmer interglacial conditions such as the present day. In central Greenland temperature changed about 25 degrees C between glacial and interglacial timesiii and in central East Antarctica, temperatures varied 8 degrees C.iv

Greenhouse gasses trap solar energy and are an important factor in warming the Earth. Research results on the Vostok ice core demonstrate the strong coupling of greenhouse gas concentration with temperature though glacial-interglacial cycles over the last 420,000 years.iv Measurements of atmospheric carbon-dioxide concentration at the South Pole show that the present concentration of carbon dioxide is higher than at any time during the last 420,000 years and that it continues to increase.v This is a clear indication of how humans are affecting our environment.

A large fraction of Antarctic research supported by the Foundation is aimed at observing present conditions to understand interactions between the atmosphere, ice, and ecosystems; recovering and interpreting records of climate and ice sheet changes in the past to understand how the Antarctic system works; and gathering basic information about the ice sheets, the underlying continent, and surrounding oceans to develop a good understanding of how ice sheets affect and respond to changes in Earth's climate. The ultimate goal, of course, is to develop robust numerical models that can help us understand how the Antarctic will respond in the future.

Antarctica has three roles in climate. As I just suggested, it influences the rest of the world's climate. For example, in addition to just being big and cold, in the austral summer it reflects most of the Sun's heat back into space simply because the white ice is a good reflector. The area of Antarctic sea ice approximately doubles during the winter and shrinks back in summer. So, long-term changes in the extent of Antarctic sea ice would affect the heat budget of the planet. Some studies indicate reductions in sea ice regionally in the past few decades but there are not yet enough data to support a full understanding of any large-scale changes that may be vii

Secondly, Antarctica responds to global climate change. Scientists have long predicted that Earth's polar regions would respond earlier and more acutely than the lower latitudes. In the Arctic Climate Impact Assessment report you have heard a lot about the other end of the world, the Arctic, where sea ice is decreasing, permafrost is warming and melting, and native peoples are experiencing significant changes in their environment. In Antarctica, the most northern part of the continent, called the Antarctic Peninsula, average winter temperatures have warmed-up 6 degrees Celsius in the last 51 years.viii (Note that this is an average mid-winter temperature and not the average annual temperature discussed in the NASA testimony.) As Dr. William R. Fraser, an NSF-funded biologist, told this committee in May 2004, the species makeup of penguin populations along the Antarctic Peninsula is shifting as a result of the warming and the receding sea ice. Other changes are equally dramatic. Two years ago, the Larsen Ice Shelf broke up rapidly and dramatically, an unprecedented event in recorded history. The leading explanation for the cause of this break up is melt pond formation associated with regional warming.ix Changes indicative of warming are also evident in the Dry Valleys region near McMurdo Station. The water volume of ice-covered lakes has been generally increasing over the last three decades and there is some evidence that this trend has existed over the last century.x Related research underway is examining the effects this may have on the cold desert ecosystem in the region.

While the observations mentioned above indicate warming, much of the rest of the Antarctic seems to be cooling slightly. Unfortunately, the low density of stations throughout the continent and the short time since measurements began (e.g. no continuous records prior to 1957) limits the conclusions that can be drawn about overall temperature trends. Nevertheless, just this year scientists using satellite data showed that a portion of the West Antarctic Ice Sheet is thinning and losing ice to the sea.xi Beginning now, and running for the next two months, National Science Foundation supported scientists, in a collaborative effort with the British Antarctic Survey, will be in the Amundsen Sea Embayment part of this ice sheet collecting data to help us understand this change and what the future may hold. If the West Antarctic Ice Sheet were to disintegrate it would eventually raise sea level about 5 meters globally.xii

Finally, Antarctica records previous global change for study and understanding. The ice sheets, for example, are the world's unsurpassed history books of past climate that scientists have been able to read in considerable detail to see changes over the last 420,000 years. For example, records of atmospheric gasses from the Vostok ice core, which were produced as part of an international partnership between France, Russia, and the US, show that the concentration of carbon dioxide has not been higher than about 290 parts-per-million during this entire time. This is important when we consider that the carbon-dioxide concentration measured at the US Amundsen-Scott South Pole Station has increased steadily from about 310 ppm during the International Geophysical Year (IGY) in 1957 to about 365 ppm today. This, in turn, is an important consideration given the significant effect of atmospheric carbon-dioxide concentration in climate models. To better understand these kinds of relationships, the US Antarctic Program is preparing to drill a deep ice core in West Antarctica within a few years, so that detailed records of the past 100 thousand years in Antarctica can be compared to similar records from Greenland.

Antarctic science is improving our knowledge of climate history, adding to our ability to quantify factors that affect climate, reducing uncertainty in projections, and improving understanding of the sensitivity of ecosystems to change.xiii

Antarctic science is still at a relatively early stage of development. Antarctica was proven to be a continent only 164 years ago, and most research has taken place only since the IGY. Nevertheless, Antarctica has already served as an important sentinel of impacts on our environment. For example, twenty years ago the harmful impacts of Chlorofluorocarbons (CFC's) on our atmosphere were realized as a result of studies of the Antarctic ozone hole. American stratospheric chemists working on the ground at McMurdo Station, Antarctica, in the winters of 1986 and 1987, collected information key to determining the cause of the ozone hole. In response, the world's nations agreed to stop putting into the atmosphere the damaging CFCs that caused the ozone hole. We are still monitoring stratospheric ozone in Antarctica; the ozone hole is still there every austral spring, but now predictions indicate that it will be healed in 50 years or so. The incremental decline in stratospheric ozone over the rest of the planet has been turned around because of that work 18 years ago, by a few committed scientists in an Antarctic winter.

In another example, several years ago the Cape Roberts Project in Antarctica, done jointly by several nations including the United States, retrieved ocean-bottom sediments from beneath sea ice. Analysis showed that orbital forcing-changes in the shape of Earth's path around the Sun and of the tilt of Earth's axis relative to the orbit-were important factors driving the growth and retreat of the ice sheets during the period 20 to 24 million years ago when Earth was warmer than present, just as they have been important factors over the last 400,000 years.xiv In a final example, the International TransAntarctic Scientific Expedition has recently found signals from the El Nino Southern Oscillation in Antarctic snow samples, demonstrating the interconnections of polar and tropical components of Earth's climate system.

NSF, as the manager of the USAP, has been and remains particularly attentive to proposals for research that will help to understand Antarctica's role in the changing global climate system.

Thank you very much for the opportunity to discuss the relevance of Antarctic science to global change. Thank you also for your support of activities at NSF and for sponsoring Senate Resolution 466 supporting the International Polar Year. I would be happy to answer questions.

i "Trends, rhythms, and aberrations in global climate 65 Ma to present," J. Zachos, M. Pagani, L. Sloan, E. Thomas, and K. Billups, Science, 292, 686-693, 2001.
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ii "Fractionation of carbon isotopes by phytoplankton and estimates of ancient CO2 levels," K.H. Freeman and J.M. Hayes, Global Biogeochemical Cycles, 6, 185-198, 1992.
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iii "The two-mile time machine; ice cores, abrupt climate change, and our future," R.B. Alley, R.B. Princeton University Press, Princeton, NJ, United States. ISBN: 0-691-00493-5. 229p, 2000.
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iv "Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica," J.R. Petit, J. Jouzel, D. Raynaud, N.I. Barkov, J.M. Barnola, I. Basile, M. Bender, J. Chappellaz, M. Davis, G. Delaygue, M. Delmotte, V.M. Kotlyakov, M. Legrand, V.Y. Lipenkov, C. Lorius, L. PÉpin, C. Ritz, E. Saltzmann, and M. Stievenard, Nature, 399(6735), 429-436, Jun. 3, 1999.
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v NOAA - Climate Monitoring and Dynamics Laboratory, Atmospheric Research Observatory at South Pole Station, see
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vi "Ice core evidence for Antarctic sea ice decline since the 1950s," Mark A.J. Curran, Australian Antarctic Division, and others, Science, 14 November 2003. They argue that methanesulfonic acid concentrations from a Law Dome ice core, 22 years of satellite data, and other proxy data "strongly suggest that the sea ice extent around Antarctica has been in decline since the 1950s."
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vii "Climate Variability in the Amundsen and Bellingshausen seas," S.S. Jacobs and J.C. Comiso, Jour. Climate, 10, 697-709, 1997.
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viii "Palmer long-term ecological research on the Antarctic marine ecosystem," R.C. Smith, W.R. Fraser, S.E. Stammerjohn, and M. Vernet, in "Antarctic Peninsula Climate Variability: A Historical and Paleoenvironmental Perspective," E. Domack, A. Burnett, A. Leventer, P. Conley, M. Kirby, and R. Bindschadler (eds), American Geophysical Union, Washington, DC, Antarctic Research Series, 79, 131-158, 2004.
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ix "Climate-induced ice shelf disintegration in the Antarctic Peninsula," T. Scambos, C. Hulbe, and M. Fahnestock, in "Antarctic Peninsula Climate Variability: A Historical and Paleoenvironmental Perspective," E. Domack, A. Burnett, A. Leventer, P. Conley, M. Kirby, and R. Bindschadler (eds), American Geophysical Union, Washington, DC, Antarctic Research Series, 79, 79-92, 2004.
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x "Physical hydrology of the Dry Valley lakes, T.J. Chinn, in Physical and Biogeochemical Processes in Antarctic Lakes (ed. WJ Green and EI Friedmann), AGU Antarctic Research Series, 59, 1-51, 1993.
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xi "Latest InSAR/ICESat/CECS-NASA results from Pine Island/Thwaites Glaciers, West Antarctica (abstract)." E. Rignot, R. Thomas, G. Casassa, P. Gogineni, W. Krabill, A. Rivera, J. Zwally, in 2004 West Antarctic Ice Sheet Workshop, Sterling, VA, Sept 2004. See:
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xii "The West Antarctic ice sheet and sea-level change," R.B. Alley, and R.A. Bindschadler, in The West Antarctica Ice Sheet: Behavior and Environment, R.B. Alley, and R.A. Bindschadler, eds., American Geophysical Union, Antarctic Research Series, v. 77, 1-11, 2001.
"BEDMAP: A new ice thickness and subglacial topographic model of Antarctica," M.B. Lythe and D.G. Vaughan, and the BedMap Consortium, Jour. Geophysical Research, 106 (B6): 11335-11351, 2001.
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xiii "The Bush administration's approach to climate change," Spencer Abraham, Secretary of Energy, Science, Vol 305, Issue 5684, 616-617, 30 July 2004. "The plan is organized around five goals: (i) improving our knowledge of climate history and variability; (ii) improving our ability to quantify factors that affect climate; (iii) reducing uncertainty in climate projections; (iv) improving our understanding of the sensitivity and adaptability of ecosystems and human systems to climate change; and (v) exploring options to manage risks."
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xiv "Orbitally induced oscillations in the East Antarctic ice sheet at the Oligocene/Miocene boundary," Tim R. Naish and others, Nature, 413, 719 - 723 (18 Oct 2001), "Oxygen isotope records from deep-sea sediment cores suggest that during this time fluctuations in global temperatures and high-latitude continental ice volumes were influenced by orbital cycles. But it has hitherto not been possible to calibrate the inferred changes in ice volume with direct evidence for oscillations of the Antarctic ice sheets. Here we present sediment data from shallow marine cores in the western Ross Sea that exhibit well dated cyclic variations, and which link the extent of the East Antarctic ice sheet directly to orbital cycles during the Oligocene/Miocene transition (24.1-23.7 Myr ago). Three rapidly deposited glacimarine sequences are constrained to a period of less than 450 kyr by our age model, suggesting that orbital influences at the frequencies of obliquity (40 kyr) and eccentricity (125 kyr) controlled the oscillations of the ice margin at that time. An erosional hiatus covering 250 kyr provides direct evidence for a major episode of global cooling and ice-sheet expansion about 23.7 Myr ago, which had previously been inferred from oxygen isotope data (Mi1 event)."
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