Arctic ice is disappearing: How clouds interact with sea ice change 

What is the news? 

The Earth is warming — some parts more rapidly than others. Temperatures in the Arctic, for example, have been rising much faster than the rest of the planet. Experts, for the longest time, have attributed the crisis to how clouds interact with sea ice, essentially frozen seawater.

Decades of research have pointed that losses in Arctic Sea ice cover allow for the formation of more clouds near the ocean’s surface.

A new research by the NASA has now shown that more heat and moisture is released through a large hole in sea ice called a polynya, which fuels the formation of more clouds. This traps heat in the atmosphere and hinders the refreezing of new sea ice.

The study was conducted over a section of northern Baffin Bay between Greenland and Canada known as the North Water Polynya.

What is polynya? 

A polynya is an area of open water surrounded by sea ice. It is a patch of unfrozen seawater within the contiguous pack ice or fast ice.  

What are the findings of the research? 

First, low clouds over the polynya emitted more energy or heat than clouds in adjacent areas covered by sea ice. The polynya did refreeze, but only after the increased cloud cover and heat under the clouds persisted for about a week. It did not mean that conditions went back to normal easily. The extra clouds and increased cloud radiative effect to the surface remained for some time after the polynya froze. 

Second, the sea ice acts like a cap or a barrier between the relatively warm ocean surface and the cold and dry atmosphere above. It leads to more heat and moisture from the ocean into the atmosphere. This warming slows down the growth of the sea ice. 

Third, Arctic sea ice has declined at a rate of almost 13 per cent per decade in the last 30 years.  

Fourth, Arctic’s warming is also due to the reduction of the surface albedo effect.  

Fifth, rapid Arctic Sea ice retreat in the early 21st century was driven by several dynamic and thermodynamic feedbacks, such as ice-albedo feedback and water vapour feedback

Sixth, the response of the clouds to the polynya lengthened the time the hole remained open. They can create a thicker blanket and increase the amount of heat emitted down to the surface. The emitted heat helps keep the surface of the North Water Polynya a little warmer. 

Seventh, opening of a polynya is a very strong, distinct forcing. If there’s not a cloud response to a polynya event, we cannot expect cloud response anywhere else. 

Source: This post is based on the article ” Arctic ice is disappearing: How clouds interact with sea ice change ” published in Down to Earth on 24th September 2021.