In Search of One of Antarctica's “Holy Grails”

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, a CO2 increase of 2-4 times pre-industrial is predicted for the end of this century, conditions not experienced on our Planet since 24 Ma ago, when the Greenland and West Antarctic Ice Sheets probably did not exist, global temperatures were much higher and East Antarctic Ice Sheet was at times up to 50% smaller than today, resulting in sea level up 40 meters higher than today.

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”.

The figure on the left is ice volume estimates from Pekar and Christie-Blick (2008) between 16 and 34 Ma and Miller et al. (2005) between 34 and 45 Ma.

The figure on the right are pCO2 estimates from Pagani et al. (2005) that show decreasing values during the Oligocene, reaching pre-industrial levels by the latest Oligocene and continuing into the early Miocene. The range shown in pCO2 is due to the uncertainty involved in using carbon isotopic composition of sedimentary alkenones (13C 37:2). The green and red lines represent pre-industrial values (280 ppm) and present-day levels (385 ppm, respectively, while the shaded box represent values that are predicted for the present to occur this century (Watson et al., 2001).

Currently, the only cored strata deposited during the Greenhouse World obtained from Antarctica is the lower part of the CIRS-1 core, which extended into the upper ~3 million years of the Greenhouse World. The Offshore New Harbor Project is expected to first image sediments deposited in the greenhouse World in Antarctica in the fall of 2008. Using these data, the optimal location for drilling will be determined, which would be used for submitting a drilling proposal in the near future.

This figure shows the ages of the recovered sediments, shown by the colored bars. On the right are sea level and ice volume estimates from Pekar and Christie-Blick (2008) between 16 and 34 Ma and Miller et al. (2005) between 16- Recent and 34 to 65 Ma.

 

 

 

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