Recent climate trends

In concert with the rest of the world, the climate of Antarctica is changing. This change is seen in key climate parameters, such as the atmospheric circulation, surface air temperature, precipitation, sea ice extent, and the temperature of the Southern Ocean. Surface air temperatures are increasing, and indeed for the second half of the 20th century, the temperature increase on the Antarctic Peninsula was among the largest experienced on Earth (Steig et al., 2009). Total sea ice extent is not decreasing, as is occurring in the Arctic, but the deeper levels of the Southern Ocean are warming, similar to most other oceans. The changes are not uniform in time or space and are due to remote and proximate influences. This chapter discusses the changes in climate at the surface and the deep ocean, including the role that the leading atmospheric circulation modes play in promoting the surface change. The contributions of natural variability and anthropogenic influences are noted as they combine with the complex nature of relationships between the sea ice, the atmosphere, and the ocean to present a challenge to our understanding of the factors underlying recent changes in Antarctic climate. Woven through the discussion is the realization that establishing and understanding the current changes in Antarctic climate as well as making projections of future changes are hampered by the sparsity of observations and the limitations of climate models.