This chapter explores important questions related to environmental change that will drive research in Antarctica and the Southern Ocean over the next 20 years. The questions here are not an exhaustive list, but rather highlight important research areas:

•    How will Antarctica contribute to changes in global sea level?

•    What is the role of Antarctica and the Southern Ocean in the global climate system?

•    What is the response of Antarctic biota and ecosystems to change?

•    What role has Antarctica played in changing Earth in the past?

The following sections generally include the following subsections for each of the issues discussed:

•    Description of the global context for the issue;

•    Current trends or understanding of the issue;

•    Questions to better understand the issue in the future; and

•    Required tools and actions to better understand the issue.

2.1 HOW WILL ANTARCTICA CONTRIBUTE TO CHANGES IN GLOBAL SEA LEVEL?

Global Context

Antarctica’s ice sheets are maintained through a dynamic balance: snow and ice accumulate over the continent, flow to the margins, and are lost to the sea. Temperatures are rarely above freezing, even during summer (except in the Peninsula), and ice is primarily lost by calving or melting when it comes into contact with relatively warm ocean waters. Antarctica holds enough ice to raise global sea levels by more than 60 m (Huybrechts et al., 2000) (see Box 2.1). A big question persists: As the world warms, how much will ice loss accelerate, ice sheets shrink, and sea levels rise?

What Is Currently Known About Antarctica’s Contribution to Sea level Rise?

Earth’s geologic history provides some insight into Antarctica’s relationship with global sea levels. During the Last Glacial Maximum, roughly 20,000 years ago, atmospheric carbon dioxide concentrations were 180 parts per million by volume, one-third lower than preindustrial values (Sigman and Boyle, 2000); Earth was colder on average by about 5°C; and larger ice sheets caused global sea level to be more than 130 m lower than today (Fairbanks, 1989). Through a combination of rising atmospheric carbon dioxide levels, changes in Earth’s orientation and orbit around the Sun, and instabilities inherent in large ice sheets, a massive deglaciation occurred that caused



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