Wintertime Arctic sea ice growth slows long-term decline
- New NASA research has found that increases in the rate at which Arctic sea ice grows in the winter may have partially slowed down the decline of the Arctic sea ice cover
- As temperatures in the Arctic have warmed at double the pace of the rest of the plant, the expanse of frozen seawater that blankets the Arctic Ocean and neighboring seas has shrunk and thinned over the past three decades.
- The end-of-summer Arctic sea ice extent has almost halved since the early 1980's.
- A recent NASA study found that since 1958, the Arctic sea ice cover has lost on average around two-third of its thickness and now 70 percent of the sea ice cap is made of seasonal ice, or ice that forms and melts within a single year.
- This increase in the amount of sea ice growing in winter doesn't overcome the large increase in melting we've observed in recent decades.
- "Overall, thickness is decreasing. Arctic sea ice is still very much in decline across all season and is projected to continue its decline over the coming decades."
- In the 1980's, when Arctic sea ice was on average 6.6 feet thick in October, about 3.3 extra feet of ice would form over the winter.
- That rate of growth has increased and may continue to do so for several more decade in some regions of the Arctic; in the coming decades, we around have an ice pack that would on average be only around 3.3 feet thick in October, but could experience up to 5 feet of ice growth over the winter.
- The increased rate of sea ice thickening in winter has other implications. As ice forms at the ocean surface, it releases a lot of the salty and dense water from which it originated, which sinks and increases the mixing of water in the upper ocean.
- This is altering the seasonal balance and the salinity distribution of the upper ocean in the Arctic; it's changing when we have fresh water, when we have salty water and how deep and seasonal.
- "And that's all going to mean that local micro-organisms and ecosystem have to adapt to these rapidly evolving conditions."
- By the middle of the century, the strong increase in atmospheric and oceanic temperatures will outweigh the mechanism that allows ice to regrow fastest, and the Arctic sea ice cover will decline further.
- The study predicted that the switch will happen once the sea is less than 1.6 feet thick at the beginning of winter.
