Arctic and Antarctica
Daily Earth Science Hydrosphere Repost

The Arctic and Antarctica: Two different versions of polar ice

The earth’s polar regions conjure up images of vast ice-covered oceans, creating white caps at the top and bottom of the globe. But fundamental differences separate the Arctic and Antarctic. These differences affect annual cycles of sea ice formation, and they control the amount of water locked away in a deep freeze at each pole. How and when the ice melts in each of these regions as the planet warms also differs.

Vast geomorphic differences between the Arctic and Antarctica control how these areas respond to bitter cold at the polar extremes.  The North Pole region consists of an ocean surrounded by land. North America, Eurasia, and Greenland rim the Arctic ocean, leaving the actual location of the North Pole stranded in an icy sea.

Antarctica, however, is a continent surrounded by ocean. The south pole sits firmly on land in the middle of the continent. Ice accumulates across Antarctica in the form of thick glaciers and snow-covered plateaus. Continental rock at the south pole’s physical location is about 100 meters above sea level, but this rocky surface lies below 2,700 meters (9,000 feet) of ice. The north pole, in contrast, supports only 3 meters of ice.  

So, Antarctica holds 90 percent of the earth’s ice, and the remaining 10 percent, in the Arctic, is primarily found in the Greenland ice cap. Geography is everything when it comes to ice caps because thick ice requires continental landmasses, not open water. 

Sea Ice

Sea ice forms during winter seasons in both polar regions, and when summer’s heat returns, much of that ice melts. But the Arctic is better suited for retaining sea ice over the summers. An average of about 40 percent of the Arctic sea ice survives the summer, whereas the Antarctic seas only keep about 15% of the winter sea ice.

Even the ice that does form differs between the northern and southern extremes. Antarctic sea ice is thin (~ 1 meter) compared to Arctic ice that averages 3 to 4 meters thick. But in the winter, southern sea ice covers about a million more square miles of the ocean than in the Arctic. 

Geography is at play again in these sea ice differences. Arctic sea ice covers the North Pole at the coldest location in the region. But Antarctic sea ice starts thousands of kilometers away from the coldest area since the South Pole is in the middle of the continent. The southern waters where sea ice forms are warmer and saltier than in the Arctic, and thus the ice is thinner. 

The areal extent of Antarctic sea ice is greater than in the Arctic because the southern ice extends northward unimpeded by land. But the Arctic Ocean is surrounded by land, where coastlines stop the spread of sea ice.

The Southern Ocean and the Antarctic Circumpolar Current

The only place in the world where an ocean current can circumnavigate the globe and return upon itself like a mythical ouroboros is in the southern hemisphere. There, unconstrained by continents and driven by westerly winds, the Antarctic Circumpolar Current (ACC) endlessly circles the globe flowing from west to east, surrounding the continent of Antarctica.

 The ACC extends from the sea surface to depths of 4000 meters. A nickname for the ACC is the “giant mixmaster” because it connects the Atlantic, Pacific, and Indian Oceans. When water from one of these oceans entrains in the ACC, it flows into the other two oceans.

The Arctic has no equivalent to the ACC. However, the Circumpolar Current is partially responsible for keeping Antarctica in a deep freeze. This deep, cold mass of circulating water provides a barrier to heat transfer, keeping the warmer northern waters at bay. 

But climate change may be disturbing this balance. The Circumpolar Current creates an upwelling of frigid deep ocean waters along the edges of Antarctica. As deep ocean waters warm, the ACC may start propagating heat to Antarctica instead of blocking heat.

Recent research shows that western Antarctica is melting faster than the eastern side of the continent. Warming in the Bellinghausen and Amundsen seas off the west coast of Antarctica is a potential culprit. Warming ocean surface temperatures create atmospheric warming, and then the ice comes under attack from the ocean and the air, thus accelerating melting. More work is needed, however, to fully understand this asymmetrical warming between western and eastern Antarctica.

Warming polar regions create plenty of climate change issues. But because of geographical and geomorphological differences between the Arctic and Antarctica, climate change threats posed by each region are different.


ArcheanWeb:

Denman Canyon, threatening the heart of Antarctica (Source: ArcheanWeb) – https://archeanweb.com/2020/03/30/denman-canyon-threatening-the-heart-of-antarctica/   Also:

The collapse of Antarctic ice shelves (Source: ArcheanWeb) – https://archeanweb.com/2020/02/14/collapse-of-antarctic-ice-shelves/  Also:

The Antarctic Circumpolar Current: An Ouroboros (Source: ArcheanWeb) – https://archeanweb.com/2020/01/29/the-antarctic-circumpolar-current-an-ouroboros/  Also:


Source:

A possible explanation for why West Antarctica is warming faster than East Antarctica (By Bob Yirka; Phys.org) – https://phys.org/news/2020-06-explanation-west-antarctica-faster-east.html  Also:

South Pole (Source: National Geographic) – https://www.nationalgeographic.org/encyclopedia/south-pole/  Also:

Ice, Snow, and Glaciers and the Water Cycle (Source: USGS) – https://www.usgs.gov/special-topic/water-science-school/science/ice-snow-and-glaciers-and-water-cycle?qt-science_center_objects=0#qt-science_center_objects  Also:

Feature Image: Ice Maiden Team (Modified) – By British Army – British Army, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=90712691  

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.