The Earth's climate is changing most rapidly in the polar regions. These high-latitude changes have local and global implications for the Nation. Sea-level rise poses risks to coastal energy infrastructure. Reductions in Arctic sea ice are leading to increased exploration for fossil fuel resources and to increased commercial transport through the Arctic. Warming at high latitudes appears to impact mid- and low-latitude weather extremes through changes in atmosphere and ocean circulation.  The HiLAT project was created to answer high-latitude climate change questions important to the U.S. Department of Energy (DOE) and the nation, through targeted application of global modeling and analysis capabilities for representing evolving polar processes and their impacts.

We are using climate model simulations to quantify feedbacks between the cryosphere and the Earth's heat and water budgets to improve our projections of high-latitude climate change and the resulting regional and global impacts. Examples of questions we will address are:

• Are changes in Arctic sea-ice cover, combined with tropical Pacific changes, influencing mid-latitude weather extremes?
• How do recent changes in Arctic and Antarctic sea ice impact marine and ice ecosystems and polar clouds?
• How do freshwater and nutrient inputs from ice sheet melting (Greenland and Antarctica) and Arctic river inputs affect marine ecosystems, aerosol production and carbon sequestration?
• Does enhanced freshwater input from the Antarctic ice sheet contribute to Southern Hemisphere sea-ice expansion through changes in Southern Ocean stratification?
• Will changes in Arctic Ocean circulation and connections with the Atlantic Meridional Overturning Circulation (AMOC) change decadal variability in the climate system?
• How will the Southern Ocean overturning and Antarctic Bottom Water formation respond as a result of competing changes in atmospheric wind forcing, upwelling, sea-ice changes and fresh water inputs from ice sheet melt?
• Is polar amplification weaker in the Antarctic due to water vapor transport and lapse rate feedbacks resulting from changes in land mass and sea-ice distribution?