Stop what you are currently doing and take a moment to study the above image. You don’t need to look too closely to see the blue area with a orange outline around it. That is the Amundsen Sea. And it is ice free. That outline illustrates where the sea ice has always been at this time of year. Always, well at least for the first time in satellite record history.
A February 13, 2017 post by Andrea Thompson, of Climate Central reports on the deeply disturbing fact that Sea Ice has hit record lows at both poles and in the case of the Amundsen Sea ice free. The post notes that the Antarctica continent is surrounded by an ocean that has a lot of variability sea ice levels from year to year while the Arctic has a ice filled ocean surrounded by land.
For several of the past few years, the sea ice that fringed Antarctic reached record highs. That growth of sea ice could have potentially been caused by the influx of freshwater as glaciers on land melted, or from changes in the winds that whip around the continent (changes that could be linked to warming or the loss of ozone high in the atmosphere).
But this year, a big spring meltdown in October and November suddenly reversed that trend and has led to continued record low sea ice levels as the summer melt season progressed. On Monday, Antarctic sea ice dropped to an all-time record low, beating out 1997.
Sea ice has been particularly low in the Amundsen Sea region of Western Antarctica, thanks to unusually high temperatures there. But it’s not clear what is ultimately driving this dramatic reversal in Antarctic sea ice, or whether it will be temporary or marks a longer-term shift.
“No one knows for sure what will happen, as there might be a rebounding from the very large decreases last year, or there might be a continuation of those decreases,” Claire Parkinson, a NASA sea ice researcher said in an email. “Whichever way it turns out, the added information will probably help scientists to get a better handle on the likely causes.”
NASA’s Earth Observatory notes the critical role that sea ice performs in helping the ice shelves hold back the land based glaciers from spilling into the sea raising sea levels worldwide.
One concern related to Antarctic sea ice loss is how the relationship between land and sea ice will change. Ice shelves partly rest on land and partly float, and sea ice is thought to stabilize the edges of these shelves. Ice shelves frequently calve icebergs—a natural process that is not necessarily a sign of climate change. But the rapid disintegration and retreat of an ice shelf (such as the collapse of Larsen B in 2002) is a warming signal.
Although sea ice is too thin to physically buttress an ice shelf, intact sea ice may preserve the cool conditions that stabilize a shelf. Air masses passing over sea ice are cooler than air masses passing over open ocean. Sea ice may also suppress ocean waves that would otherwise flex the shelf and speed ice shelf breakup.
The interaction between sea ice loss and ice shelf retreat merits careful study because many ice shelves are fed by glaciers. When an ice shelf disintegrates, the glacier feeding it often accelerates. Because glacier acceleration introduces a new ice mass into the ocean, it can raise global sea levels. So while sea ice melt does not directly lead to sea level rise, it could contribute to other processes that do. Glacier acceleration has already been observed on the Antarctic Peninsula.