Tom Neumann: Is East Antarctica warming or cooling?

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Recent studies suggest cooling in parts of East Antarctica. Other studies suggest the possibility of warming. Why don’t scientists know for sure?

Scientists do know that Antarctica as a whole is the only one of Earth’s major continents that hasn’t shown a consistent and clear picture of warming temperatures in recent years.  They know that coastal regions in Antarctica – such as the Antarctic Peninsula, which extends up toward South America – are clearly warming.  West Antarctica is also clearly warming. But East Antarctica appears to be behaving differently from other parts of the continent. NASA polar scientist Tom Neumann told EarthSky:

Antarctica is a large reservoir of water that’s locked up on land. If the ice sheet gets larger, sea level falls. If the ice sheet gets smaller, sea level rises.

In fact, contrary to most of the rest of the globe, East Antarctica – a region comprising about three-quarters of Antarctica, as big as the United States and several times bigger than West Antarctica – might well be cooling in parts.

Definitive answers are difficult. Scientists point to multiple time scales for climate change. Seasonal changes also complicate the picture. But the biggest difficulty is that Antarctica is extremely cold and remote, which is why scientists have only about 20 to 30 years of climate data for the entire continent.

The most direct way to measure how temperatures are changing in Antarctica is to set up weather stations, and there are now about 20 to 30 automatic weather stations in East Antarctica.  They are transmitting data about temperatures and wind speeds back to data centers in the United States and throughout the world.

However, those weather stations are relatively recent innovations in Antarctica. Long-term direct measurements of temperatures in Antarctica do not exist.

In that sense, if you imagine a place as big as the United States with, for example, a weather station in Utah, one in Vermont, and another one in Missouri, you can see that it would be hard to know how the temperature has been changing in California, or other places that you have not been measuring.

Why warming in some parts, while cooling in others?

With only limited data to rely on for answers, Antarctica appears to be warming in some places, and perhaps cooling, or staying the same, in others. Why would that be?

Antarctica is completely surrounded by the Southern Ocean. Data suggest that this ocean is warming.

In West Antarctica and the Antarctic Peninsula, some data suggest a warming of the surrounding ocean by several degrees. The ocean is a large reservoir of heat, and if the ocean is warming it would make sense that West Antarctica and the Antarctic Peninsula would then warm up as well, or have changes in precipitation such as snowfall.

For places farther from the coast, such as the interior of East Antarctica, atmospheric circulation above the ice sheet might be a factor. How wind patterns change through time, and whether the winds bring more or less warm air in from the coast, might determine temperatures in the interior of the continent.

In some ways, it might be possible to compare warming and cooling in Antarctica to a frozen turkey in an oven. The outer parts of the turkey might be heating up, even as the inner part stays frozen.

This comparison might hold true for the continent of Antarctica.

Satellite data may soon reveal temperature trends

The advent of satellite data should ultimately reveal long-term trends.

Antarctic Skin Temperature Trends between 1981 and 2007, based on thermal infrared observations made by a series of NOAA satellite sensors. Skin temperature trends do not necessarily reflect air temperature trends.

In particular, microwave data has been used since the late 1970s to look at the uppermost surface of the Antarctic ice sheet.  Eventually, perhaps soon, the data will begin to show how this Antarctic “skin temperature” has changed over a period of several decades.

Another interesting study has involved thermometers inserted directly into boreholes in the ice sheet, in order to measure temperature change. Antennas and other equipment left on the ice sheet help transmit the temperature measurements back to the United States, to show how the ice temperature is changing through time at the measurement sites.

At most of the sites, the thermometers are showing a small degree of warming, about a half a degree, or in some cases less.

So the question of warming or cooling in East Antarctica hasn’t been settled yet, despite the fact that melting ice sheets in Antarctica could be major contributors to sea level rise in the 21st century. The answers are important, but, at present, scientists do not have a final or complete answer about warming or cooling in East Antarctica.

Sophie Nowicki on weak underbelly of Antarctic ice sheet

November 19, 2011

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