Blog: Changing Climate in Antarctica

Melting ice in Antarctica results in rising sea level that threatens millions of people living in coastal areas.

When the industrial revolution began in the early 18th century humans started to poor CO2 into the atmosphere. First from burning coal, later from oil and gas. Since then this anthropogenic climate change has led to a global warming of about 1°C. Unfortunately, warming in Antarctica turn out to be much faster than the global average. The West Antarctic Peninsula is one of the fastest warming areas on Earth, with only some areas in the Arctic experiencing faster rising temperatures. Antarctic Ice Sheet holds approximately 61 percent of all fresh water on the Earth. This is an amount equivalent to about 58 m of sea-level rise. In East Antarctica the ice sheet rests on a major land mass, but in West Antarctica the sea bed can extend to more than 2,500 m below sea level. The mean thickness of the Antarctic ice sheet is more than 2 km, and the maximum is almost 4800 m.

 Sea ice extent suddenly declining in November 2016

Antarctica’s sea ice has been expanding slightly in many recent years, and this has been a big theme for those who doubt global warming is man-made. The National Snow and Ice Data Centre (NSIDC) in Colorado provides daily updates of the ice condition in the polar regions. The center reports that once the Antarctic sea ice reached its annual maximum extent on August 31 – way earlier than expected – it’s been declining fast, and was in November 2016  more than 1 million square kilometers below the previous record low.

Fig 1: Credit: National Snow and Ice Data Centre

The map below show the Antarctic sea ice extent from November 1 – 30 in 2016, which is at its lowest in recorded history for the month. Scientists say it is difficult to pinpoint exactly what is happening. Winds that normally sweep around the Antarctic continent where the weakest for November in two decades and might have been a factor. Recovery of the ozone layer over Antarctica which led to cooler air might also have contributed

Fig 2 Credit: Nasa Earth Observatory

The Antarctic Ice Sheet in irreversible decline?

For half a century climate scientists have seen the West Antarctic ice sheet as a sword of Damocles hanging over human civilization. With warming temperature in both sea and atmosphere the ice sheet could begin to disintegrate, causing the sea to rise 2 meters or even more by 2100 and much worse in the century to come. The fact that the ice sheet in west Antarctica is resting on a sea bed under water makes it particularly vulnerable from warming water.

 

The Pain Island Glacier

Pine Island terminating in the Amundsen Sea (see map above) glacier has retreated roughly 50 kilometers in the last 70 years.  In November 2015 and iceberg the size of Singapore separated from the glacier, signaling its depreciating state.

Credit: Nasa Earth Observatory

The figure below show how this might happen as warming water are melting the ice from below.

 Credit: Smith et al., 2016/Nature

Prior to the break-up of the Pine Island glacier in 2015 scientists had observed a rift formed at the very base of the ice shelf 30 km inland indicating the shelf is breaking up from the inside out. A new rift was detected in November 2016 (see photo below), indicating new movements that might result in new break-ups to come. The Pine Island glacier sit at the outer edge of one of the most active ice streams on the continent. Like a cork in a bottle it blocks the ice flow into the sea. If the West Antarctic ice sheet collapses, which might happen within the next 100 years, this might lead to a sea level rise of nearly 3 meters.

 

 Credit: NASA/Nathan Kurtz.

 

The Antarctic Peninsula

The Antarctic Peninsula, the home to almost 700 hundred glaciers, has experienced a warming by more than 3°C or the last 50 years. 90 % of the glaciers are retreating. Recent research suggests that the rapid retreat stems from both the warming atmosphere and increasing ocean temperatures. You can see this on the map below. Red dots where the ocean is warming up show retreating glaciers. Blue dots are glaciers not retreating where the water is cooler water at the tip of the peninsula.

Source: Cook et al (2016)

Consequences of Climate Change in Antarctica

The most dramatic impact from the warming water and atmosphere in Antarctica is global sea level rise.  A collapse of the West Antarctic ice sheet that might happen in the lifetime of our children,  would drown cities like New York and Miami and displace 150 million people living in coastal areas world wide.

Krill often feed on algae underneath sea ice and will decline when the ice decrease. Adélie penguin populations have been declining in recent years from reductions in krill populations and changing weather conditions in their traditional nesting areas. Emperor penguins are highly vulnerable as well. Another specie identified to be highly vulnerable to climate change is the Antarctic tooth fish. Climate change in Antarctica will thus have dramatic effects both globally and locally.

 

 


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