Summary of current polar ice status
- Antarctic land ice melt is 6X faster than 1980’s rate:
- A massive cavity has been found inside the Thwaites Glacier, indicating a rapid collapse in progress
- East Antarctica, once thought stable, is in the early stages of collapse. This includes the Totten Glacier, which drains the East Antarctic Ice Sheet.
- Antarctic sea ice is at historic lows
- “Old” Ice is disappearing in the Arctic. This is the sea ice that previously did not melt during the summer. Young ice melts much faster each year.
- Overall, ice is thinning as well as losing total area.
- The Greenland Ice Sheet is crossing a tipping point.
- GLOBAL WEATHER EFFECT: When polar sea ice melts, the jet stream goes haywire. The extreme weather we are now experiencing is partially attributable to loss of Arctic sea ice.
Types of Ice / Their Roles at The Poles
Polar ice plays a large part in regulating and stabilizing global weather. When massive areas of ice disappear, everything changes. That is what is happening now.
There are three types of ice that play a role in global warming. It is important to distinguish among them when discussing the affects of melting ice and the resulting feedback loops have on climate change patterns.
The key characteristic of land ice is that it has not previously been in the ocean. When it melts, it contributes to the total volume of water in the oceans. There are hundreds of feet of sea level rise locked into the ice sheets of Greenland and Antarctica.
Slowdown of global currents (including the critical Gulf Stream) is driven by freshwater pouring into the ocean from melting glaciers on Greenland and Antarctica. Differences in salinity between depth layers drive the global overturning current.
This hybrid ice class is critical to the rate of melt for onshore ice sheets. To a large degree, ice shelves are what is holding back the flow of glaciers into the ocean, especially in Greenland and Antarctica. As the ice shelves of Antarctica break up in dramatic fashion, the land ice behind them begins to flow faster. That is what is happening now.
Ice that floats in the water and its affect on climate is tricky to measure, but the general trends are crystal clear. The extent of ice pack decline has been verifiable for decades, with the total area covered reduced by about 70% since 1978. Equally important, but harder to measure, is ice thickness, which can now be measured by satellite. Compared to the lowest extent year of 2012, this year’s extent is slightly greater, but the all important class of “multi-year” ice is far less. The thickness of the remaining ice is also starkly less.
“The Arctic is going through the most unprecedented transition in human history,” Jeremy Mathis, director of NOAA’s Arctic research program, said at a press conference. “This year’s observations confirm that the Arctic shows no signs of returning to the reliably frozen state it was in just a decade ago.”
The rapid melting of sea ice is one of two major polar feedback loops that are accelerating global warming beyond the point of no return. Read more about feedback loops.