By David Harwood and Richard Levy
Concerns for our warming planet are now receiving considerable attention in the U.S. media, attention that is relevant and well deserved. Many policy-makers are finally addressing global climate change issues, which have taken center stage as we head into the coming presidential election. The scientific community continues to engage in international collaboration to bring accurate projections of warmer-than-present future scenarios into these discussions. Receipt of Nobel Prizes by Al Gore for An Inconvenient Truth
and by scientific members of the IPCC (Intergovernmental Panel on Climate Change) indicates the importance and international recognition of climate-change issues. As these issues are discussed in the public forum, we note that the following questions are commonly asked: What does future climate warming mean for us? Aren’t these changes part of natural cycles in climate change? Hasn’t Earth been warmer in the past?
Much of our knowledge of the last one million years of climate change comes through the recovery and study of ice cores from polar ice sheets. Annual layers of snow accumulate and are progressively buried to great depth in ice sheets. As the snow turns to ice, it traps air from ancient times within bubbles between the ice crystals. This trapped air, and the composition of the ice crystals, provides a very important history of the amount of carbon dioxide (and other gases) in our atmosphere. Past temperature changes can also be determined, and variations reveal that a regular cycle of climate change has occurred with a 100,000-year periodicity. This natural cycle of nearly coincident change in atmospheric temperature and CO2 over the last one million years is well understood, and is predicted by changes in the Earth’s orbital patterns. A natural cycle of CO2-influenced “greenhouse effect” and “inverse greenhouse effect” has controlled this cyclic pattern of glacial and interglacial changes. If allowed to progress naturally, without human interference, Earth would start to cool toward the next glacial period within the next 10,000 to 20,000 years. However, the last 150 years of our industrialized society’s development has interrupted this natural cyclicity and abruptly increased the amount of carbon dioxide in the atmosphere, well beyond the level of natural variability. An observed global temperature increase is the natural consequence of this human-induced elevation in CO2.
There are now clear signs of global temperature rise, sea-level rise, disappearing Arctic ice cover, increased melting of polar ice sheets and mountain glaciers, and thawing permafrost and tundra. The IPCC has projected that global temperatures may increase by up to 5 degrees Celsius within the next 100 to 200 years. Where will these increased temperatures lead us? What will the future hold? In order to address these questions, we must look to our planet’s historic records in geological sedimentary archives, to times when Earth was indeed 3 to 5 degrees Celsius warmer than today. The most recent times when Earth experienced this level of warming was during the early Pliocene Epoch and middle Miocene Epoch, four to five million years ago and 17 to 15 million years ago, respectively. These times predate the evolution and existence of modern humans and represent a global environment that was vastly different than that in which we thrive today.
Global warming will be higher in Earth’s Polar Regions, with smaller temperature increases in lower latitudes. Warming in the Polar Regions is having, and will continue to have, a substantial impact on our global environment. Sea level will continue to rise as water, currently locked up in continental ice sheets on Greenland and Antarctica, is released to the world’s oceans. Ocean circulation patterns will change when fresh water input modifies the density of polar water masses, and when cold, salty bottom-water production decreases as sea ice and ice shelves disappear. Using climate and ice-sheet models, scientists are working to predict the rates of temperature change, the impact on ice-sheet stability and the rate of resultant sea-level rise, as the ice sheets melt. However, there is still much we do not know about the behavior of ice sheets and ice shelves, as indicated by the surprisingly rapid collapse of the Larsen B Ice Shelf in the Antarctic Peninsula in 2002.
By studying archives of climate history that are preserved in the sedimentary rock record around the Earth, we can begin to understand how the Earth system, and the cryosphere (ice sheets, ice shelves, glaciers, sea-ice, etc.) in particular, has functioned during past periods of global warmth. Geologic records recovered from deep-ocean drilling provide a record of past oceanic conditions that can be linked to changes in polar ice. But these records come from locations that are far from the polar regions where these changes occur. To understand how ice sheets have responded to past warmth, we must go to the “source” and obtain these historic sedimentary archives of environmental change from high latitude settings, next to the ice sheets. By obtaining and studying many past examples of transitions from glacial “ice-age” conditions to interglacial (warm) conditions, we will learn much about the natural variability of ice sheets and the environmental factors that control these changes. Evidence of these transitional periods of climate and ice-sheet change is preserved in the sediments and fossils deposited in the ocean basins near Antarctica.
Over the past two Antarctic summer field seasons, an international group of scientists has been actively exploring the geological history of the Antarctic continent to document how this critically important region responded during numerous past warm periods.
The ANDRILL (ANtarctic geological DRILLing) Program is a multinational collaboration comprising more than 200 scientists, educators, students, technicians, engineers, drillers and support staff from Germany, Italy, New Zealand and the United States. ANDRILL’s goal is to uncover the elusive geological history of Antarctica and let the public, other scientists, and policy-makers know about the continent’s past and probable future by recovering sediment core samples by drilling around the Antarctic margin. Scientific activities are coordinated through the ANDRILL Science Management Office at the University of Nebraska-Lincoln (UNL), affiliated with the Department of Geosciences. U.S. support for ANDRILL is provided through a Cooperative Agreement between the National Science Foundation and UNL.
ANDRILL’s diverse scientific community recognizes that critical questions regarding the history and behavior of past Antarctic ice cover can be addressed by drilling a series of sites on the continental margin to reveal the ice sheet’s response to past periods of global warming and cooling. New ANDRILL results are being incorporated into computer-generated ice-sheet and climate models to better understand the history and unknown future of our dynamic planet.
The two inaugural ANDRILL projects were exceedingly successful, recovering more than 2,400 meters of new rock core that provides an exquisite record of environmental change through critical intervals in Earth’s climate evolution. The drilling effort was phenomenal with the drilling crew reaching record-breaking depths of 1,285 and 1,138 meters below sea floor for each project, respectively, the two deepest drill holes in Antarctica to date. ANDRILL’s McMurdo Ice Shelf Project was drilled last year (October 2006 to January 2007) and recovered a history of the last 14 million years of growth and melting of the West Antarctic Ice Sheet (WAIS), including a snapshot during the warm early Pliocene period, the transition to colder dynamic conditions during the late Pliocene, and the onset of a “persistent” WAIS within the last ~800 thousand years. More than 60 cycles of glacial to interglacial change were recovered in total. This year, the Southern McMurdo Sound Project successfully completed drilling operations last month (October to December 2007), recovering a climate history from pieces of time throughout the last 20 million years. Rock core recovered includes an expanded sedimentary section through the warm middle Miocene period, the project’s primary target. Both drilling projects were supported by the ANDRILL Operations Management Office at Antarctica New Zealand. Fifty-six scientists, educators, technicians and support staff from the four partner nations worked for more than two months in the Crary Science and Engineering Center at the U.S. McMurdo Station.
ANDRILL is one of the larger projects operating during the fourth International Polar Year (IPY - www.ipy.org
), 2007–2009. IPY-4 continues the tradition of international science years and includes multidisciplinary research operating in both Polar Regions, involving scientists from over 60 countries. In addition to the important scientific research conducted during IPY, this celebration of polar science offers a timely opportunity to engage students in discussion about climate change and enhance scientific literacy. Through IPY we can help prepare the next generation to face future environmental challenges well armed and empowered to mitigate and remedy the climate problems they are inheriting.
For this reason, the ANDRILL Program has developed and maintains an engaging and diverse education and outreach program. Please visit ANDRILL’s Project Iceberg
to find videos, podcasts and blogs from scientists and educators in Antarctica that describe ANDRILL activities. When we speak to schools and youth groups, we recognize the concern and fear that our message about climate change may impart to our young audience. We encourage them to learn more about the issue, hone their skills and interest in math, science and inquiry, and strive to make a difference in the future.
ANDRILL scientists will continue to study these new rock cores in the coming years to learn more about Antarctic climate history. We will report in the next issue of Prairie Fire on these two ANDRILL drilling projects, the initial results of what we are learning from our studies, and discuss what this means for past and future climate change. We are also actively planning the next drilling expeditions to the southern continent, in order to investigate other key intervals of the geological past through the ANDRILL rig, a geological “time machine” for scientific discovery.
In addition to their 15-year collaborative effort in Antarctic research, each summer Levy and Harwood teach a three-week geoscience field course for UNL Education majors, camping and investigating geological processes and Earth history around Wyoming, Nebraska and South Dakota. This course involves scientific inquiry, discovery-based learning and exposure to geology in the field. Their goal is to provide future science teachers increased teaching proficiency, confidence in presenting science content and practice in effective pedagogy.
Please visit the Web site andrill.org for more information, and contact the ANDRILL Science Management Office at UNL for a schedule of public presentations and educational resources available from the ANDRILL Program.