A recent study by NASA found that sea ice is growing faster during the winter months today than it did decades ago. This increased growth of sea ice has helped to slow down the overall reduction in Arctic sea ice and delayed an ice-free Arctic.
NASA makes sure to clearly note that this doesn’t mean climate change isn’t taking place, that our planet is not warming and that the overall amount of sea ice isn’t declining in the Arctic.
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Temperatures in the Arctic have warmed much faster than temperatures in tropical locations. The doubled rate of warming has led to increasingly smaller sea ice extents during Arctic summer months and an overall reduction in sea ice.
The graph above by NASA shows an average 12.8 percent decline in average September sea ice extent, with the rate of decline increasing since the 1990s.
So how can it be that sea ice is declining in the Arctic but wintertime growth is increasing? The story lies in the magnitudes of both changes. While the Arctic sea ice is growing faster and higher during the winter months, it is more than offset by the melting in the summer months. So what we’ve seen is that the increased rate of sea ice growth in the winter helps to mitigate the melting during the summer. However, ultimately the warming summer temperatures continue to overall reduce the extent of sea ice.
Over the past few decades, sea ice across the Arctic Ocean has gotten smaller and thinner. Compared to the 1980s, today’s end-of-summer Arctic sea ice extent is about half. Since 1958, Arctic sea ice lost about two-thirds of its thickness, with nearly three-quarters of Arctic sea ice forming and melting each year.
The NASA research team found that in the 1980s, sea ice on average in the Arctic was 6.6 feet thick in October. From there, on average 3.3 more feet of sea ice would form through the winter. Comparing that to today, where average sea ice in the Arctic is 3.3 feet thick in October but will grow on average 5 feet more of sea ice through the winter. Hence, the combined sea ice thickness in the 1980s was 9.9 feet thick, compared to 8.3 feet thick today.
The negative feedback of increasing rate of wintertime sea ice growth will help slow down the overall decline in Arctic sea ice. However, the seemingly inevitable ice-free Arctic will win out in the end, adds NASA.
Another positive factor of the increased growth in wintertime Arctic sea ice is the impact it has on global circulation. While global ocean circulation continues to slow down, increased Arctic sea ice growth could help to mitigate the slowing.
As a quick overview, global ocean circulation is slowing down because overall Arctic ice levels are continuing to decline, causing a freshwater influx into the Northern Atlantic Ocean and a “cap” on the mechanism that drives global ocean circulation. By increasing the rate at which wintertime sea ice forms, the freshwater cap could be limited for a time.
This is another example of how Earth’s systems work to counterbalance and mitigate changes in some systems, much like the three branches of the US government.
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