Investigating the Tipping Point from the Greenhouse to Icehouse World of the Past in Antarctica
Today, the climate is changing faster than any time of the last 65 million years, with rising temperatures occurring at an alarming rate. Warmer ocean sea surface temperatures are feeding ever more powerful hurricanes, while mega heat waves and droughts are occurring in record numbers. Moreover, thawing glaciers and melting of the sea ice are shrinking at rates that are far quicker than what even the most pessimistic climate models have predicted.
A growing body of knowledge indicates that these changes are due to increased concentrations of greenhouse gases such as CO2 in our atmosphere. Predictions of future atmospheric CO2 levels expected to occur by the end of this century range from 500 to 900 ppm. The last time that atmospheric CO2 levels were this high occurred between 25 and 40 million years ago. During this time, the Antarctic ice sheet was far more dynamic, retreating hundreds of miles inland during warm periods, which resulted in sea level rises of over a hundred feet, while during colder periods, the ice sheet expanded across the Antarctic shelf and grew in some case to larger than today. Additionally, it was also during this period (~34 million years ago) that one of the most dramatic and permanent climatic changes occurred of the last 100 million years: the abrupt change from greenhouse world conditions (older than 34 million years ago) in which ice sheets were either absent of ephemeral in nature to an icehouse world in which large continental sized ice sheets expanded across Antarctica (<34 million year ago). Scientists are still struggling to understand what were the causal mechanisms that resulted in this tipping point that switched the world climate dramatically especially in Antarctica. State-of-the-art climate models, combined with paleoclimatic proxy data suggest that the main triggering mechanism for initial inception and development of the Antarctic Ice Sheet were the decreasing levels of CO2 concentration in the atmosphere and that the opening of critical Southern Ocean gateways only played a secondary role. Additionally, as this time interval is the last time that atmospheric CO2 was as high as what is predicted for this century and was considerably warmer than today, studying this period may be able to provide us with a glimpse of our future.
If all of the world’s ice sheets melted, sea level would rise by approximately 230 feet. This is a representation of how New York Harbor would look in an ice-free world.
From K. Miller, Rutgers University
Although a wealth of data from deep sea and terrestrial records provide a detailed story of climate changes at low and mid latitudes, first-order questions remain about how climate and the ice sheet changed in Antarctica. Resolving these questions is important as polar ice affects global sea level, ocean circulation heat transport, marine productivity and planetary albedo and are key pieces in understanding the modern climate system. With current rising atmospheric greenhouse gases, resulting in rapidly rising global temperatures (IPCC, 2007) studies of Polar climates are prominent on the research agenda. Antarctic ice sheet dynamics and stability is of special relevance because, based on IPCC 2007 forecasts, an increase of 2x CO2 for the end of this century is expected, conditions not experienced on our Planet since 24 Ma ago, when only the Antarctic Ice Sheet existed and global temperatures were much higher.
Clearly a better understanding of the evolution of Antarctic ice sheet and its climate is needed for these critical time intervals when climatic tipping points occurred. However, a paucity of data currently exists from near or on the Antarctic continent. This is due in part to the difficulty in conducting an expedition in this cold harsh region. In fact, many scientists now agree that the key to the climate puzzle lies literally at the bottom of the Earth: Antarctica. However, so far no one has recovered a continuous core record on the Antarctic continent or on its shelf from when the Earth was in a Greenhouse World (>34 million years ago). In fact, for many Antarctic scientists, recovering sediments from this period are considered to be one of Antarctica’s “Holy Grails”.
Exploring Undiscovered Country: Drilling the Greenhouse World to Icehouse Transition in Antarctica
Starting last fall and continuing until the spring of 2009, the International Polar Year (IPY) will mark a global effort to understand how patterns of present and past climate change at high latitudes can help scientists better understand and forecast future climate conditions. During these two years, a massive effort will be made to collect critical data sets for better understanding this period. One of these efforts will be the Offshore New Harbor Project, which will first image strata located below the sea floor that were deposited when the Earth was in a Greenhouse World and the Antarctic ice sheet were either absent of ephemeral in nature. This project is part of the ANDRILL Program, which "is a multinational initiative with the objective to recover stratigraphic core records for the use of interpreting Antarctic’s climatic, glacial, and tectonic history for the past 50 Ma".
The Offshore New Harbor Seismic and Gravity Expedition (October-December, 2008)
The Offshore New Harbor Project is targeting strata that are located off the coast of East Antarctica in the western most Ross Sea. The goal of the Offshore New Harbor (ONH) Project is to study sediments deposited in Antarctica during the Greenhouse World (>34 million years ago, Ma) and the transition into the Icehouse World (34-24 Ma). Although evidence suggests that significant thicknesses of Greenhouse sediments exist below the sea floor offshore of New Harbor based on down dip locations from New Harbor, previous expeditions have failed to image these sediments. This year a team of scientists, students, and a school teacher live on the sea ice to seismically image Greenhouse sediments that lie beneath the sea floor in the New Harbor area. Using new technology, this expedition promises to explore undiscovered country by imaging and reconstructing these sediments that were deposited during the Greenhouse World (45-34 million years ago) as well as across the transition from the Greenhouse to Icehouse World (34-25 million years ago). The objective of this expedition will be to locate the optimal site to drill these sediments in the near future.
In early October, the ONH team will fly from Christchurch, New Zealand to McMurdo Station, the largest base in Antarctica. This is the early spring in Antarctica and temperatures typically are in the minus 20’s Fahrenheit (plus wind chill). After they are given training on how to survive on the sea ice, they will traverse by vehicles across the sea ice of McMurdo Sound to offshore of New Harbor. There they will conduct the seismic and gravity survey, while living on the sea ice and sleep in unheated tents. It is planned that they will be on the sea ice for about 35 to 40 days. The location is among the most beautiful in Antarctica, with towering mountains and active and extinct volcanoes surrounding the camp on three sides. The team will include Dr. Pekar (lead PI, Queens College, CUNY), Marvin Speece (Co-PI from Montana Tech), Ms. Brown, a teacher at the Promise Academy, which is part of the Harlem Children’s Zone, as well as three students from Queens College.
Seismic Data Study
The seismic study consists of two seismic dip profiles, one of which will be slightly oblique to dip. The primary aim of each seismic line is to identify site locations to sample Greenhouse World sedimentary archives older than what was recovered at CIROS-1. Because of the complex structural nature of this area, ages of the oldest strata may differ among the sub basins, therefore our strategy is to image different parts of this area to maximize our efforts in finding the optimal location to drill Greenhouse World sediments. These seismic lines will tie the CIROS-1 and MSSTS-1 boreholes to the TS05-01 MCS line taken in 2005, providing the first opportunity to correlate the deeper reflectors to the older strata sampled in these boreholes (see figure above).
Seismic line ONH-1 will be up to 30 km long, crossing over the CIROS-1 and near the MSSTS-1 boreholes and cross the MCS TS-05-01 line. By extending the line up to 10 km beyond CIROS-1, potential drilling targets will be evaluated in the direction of Taylor Valley. Additionally, this line will permit correlation of Oligocene and Eocene strata into over sea ice MCS data collected in 2005. Although this is a relatively long line, the first 20 km will be over relatively smooth, thin (~2 m) sea ice, based on sea ice that broke out in this area in late austral summer of 2007. Based on previous experience, we expect to collect 2.5 km or more per day.
Seismic line ONH-2 is a dip line that will begin one km eastward of ONH1 and continues 15 km updip in the direction of Ferrar Valley to evaluate potential drilling targets in this area.
These seismic lines will image a number of important objectives for the first time.
- ONH-1 seismic lines will permit the imaging of Oligocene and uppermost Eocene strata recovered at CIROS-1 and MSSTS-1.
- Line ONH-1 will provide continuous seismic coverage from MSSTS-1 drillhole to marine seismic data that extends into the Ross Sea as well into the MCS seismic data collected in 2005, tying for the first time these borehole data to MCS data. This will provide a greater understanding of the stratigraphic and tectonic evolution for this region. It will also enable correlating seismic reflections of older strata imaged in ONH-3 around to the CIROS-1 borehole.
- ONH-2 will image strata offshore of Ferrar Valley to evaluate the stratigraphy and tectonic structures of this area for the first time.
- Both seismic lines are expected to cross the TAM fault, providing constraints on its location and geometry.
- Both lines will also image the basement reflectors for determining the structural geometry of the ONH and Blue Glacier areas.
Introducing Under Represented Minority Students to Climate and Earth Science -There will be a strong educational and outreach component to this expedition, through collaboration with Queens College (CUNY) and the Promise Academy and the Harlem Children’s Zone. This is a unique opportunity to develop an integrated learning and mentoring program for middle school students from public schools located in east Harlem. The Promise Academy (PA) has been cited and described by educators and the media (e.g., CBS’s “60 Minutes”, Time Magazine, etc.) alike as a bold attempt at presenting quality education to the students of Harlem, New York City.
A number of activities are planned leading up to the start of the expedition, and include interactions with scientists, college students and middle schools students both in the classroom as well as on trips to: the core repository at Columbia University to examine sedimentary cores; to the research labs at Queens College for the students to learn about science by using microscopes to examine fossils and sediments; and the American Museum of Natural History. While on the ice, we will have internet and telephone access, which will permit teleconferencing with schools from around the country as well as sending out blogs and video and audio clips that will be posted on our website and disseminated to collaborating educational and media organizations.
Results of the Expedition: Developing a Strategy to Drill One of Antarctic’s “Holy Grails”
After the expedition, the seismic and gravity data will be processed, analyzed, and then interpreted to reconstruct the geometry of these greenhouse world sediments. This will provide clues about the depositional history of the area, resolving a number of first-order questions about the geologic and climate history of this area. It will also permit us to locate the optimal site to drill these sediments in the near future. Such a drilling project would represent a first time that cores from this time interval and region would be recovered. These sedimentary archives have the potential to allow us to unlock many of the secrets of Antarctica’s climatic and cryospheric evolution during times when the Earth was a Greenhouse World.
If you are interested in finding out more information about education or science research contact:
Dr. Stephen Pekar (Principal Investigator)
School of Earth and Environmental Sciences
65-30 Kissena Blvd.
Flushing, NY 11367
Tel. # 718 997 3305