I just read about yet another feedback mechanism I was not previously aware of:
' Freshly melted ice ... creates a layer of cold water that protects sea ice above from more melting. "It isolates the ice from the hot devil water sitting at the bottom waiting to come up" Wagner explains. Less sea ice means there will be less of that protective cold layer, leading to even more melting. '
https://www.cnn.com/2019/06/08/world/arctic-beneath-ice-intl/index.html Which got me thinking it would be useful to have an inventory of all the significant reinforcing ("positive") and suppressive ("negative") feedbacks that affect Arctic sea ice.
I did not find any forum title where this would fit, but this section seems to be the most closely related topic. It could require its own thread, similar to the Glossary.
Here is the kind of list I have in mind:
Reinforcing feedbacks:1. Melted ice creates cold layer that insulates remaining ice from warmer subsurface water. Less ice to melt reduces this insulating layer. Which leads to even less insulating cold layer water.
2. Less ice leaves darker ocean water with lower albedo, thus energy from solar radiation is absorbed into water instead of reflected. Warmer water leads to less ice.
3. Overall, fractured ice is more mobile and thus more susceptible to being exported via Fram Strait or Nares Strait. There is chance of an ice bridge to block export via Nares Strait with fractured, reduced ice cover. Increased export results in less multi-year thick ice, and more mobile young ice the next year.
4. Fractured or thin sea ice floes have more surface area per unit volume and therefore melt at lower temperatures than thicker ice, or larger ice floes. This leads to less surviving ice the summer to become thicker multi-year ice.
5. Fractured vs. contiguous ice allows more wave action that interferes with freezing of ice and allows wave action to break ice into smaller pieces less resistant to melt. Resulting in more fracturing of the remaining ice and even more wave action.
6. Albedo reduction by replacing ice with dark water leads to warmer water and more energy in the Arctic Ocean system. That in turn increases frequency, intensity, or both, of cyclones causing wave action that break up ice. Which reduces albedo even further.
7. Weakening of the Polar Cell results in more frequent occurrence of Arctic Dipole, that increases export of ice out of the Arctic, which lowers Arctic sea ice, which leads to warm Arctic Ocean water, which leads to further weakening of the Polar Cell. (whew, that's a long chain)
8. Loss of ice cover weakens the polar cell which in turn allows more incursion of of warm moist air masses from the south into the Arctic, which leads to more weakening of the polar cell.
9. Weakening of the polar cell allows more cyclonic systems to move into the Arctic. Those cyclones disrupt the Arctic sea ice, and in doing so further weaken the polar cell.
10. Younger, thinner ice has higher salt content and thus lower melt temperature. Therefore it has less chance of surviving the summer melt to become more resistant, thicker multi-year ice.
11. Reduced snow cover allows earlier spring warm up of Arctic land mass, which results in warmer air flowing onto the Arctic Ocean. This warms the system as a whole, leading to reduced snow cover and earlier snow loss the following year.
12. More open ocean leads to higher humidity and more extensive or thicker cloud cover over the Arctic Ocean in the fall and winter. More extensive or thicker cloud cover in fall and winter reduces heat loss thus reduces winter refreezing.
13. Earlier spring warm up of Arctic land mass, results in increased permafrost and land ice thaw, resulting in earlier and more melt water flowing from land into the Arctic Ocean. The meltwater warms the Arctic Ocean and reduces Arctic sea ice. Which leads to more open water with lower albedo to absorb solar radiation in the summer, increasing summer heat content of the system More open water allows this heat to escape to moderate winter air temperatures and earlier spring warm up.
14. Reduction of Arctic sea ice allows increased flow of warmer Pacific or Atlantic water into the Arctic, leading to further decline of Arctic sea ice, leading to more Pacification and Atlantification of the Arctic Ocean.
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Compensatory or Suppressive feedbacks:1. Ice cover insulates the Arctic Ocean in winter. With less sea ice cover there is faster energy loss and winter cooling, and thus faster winter ice increase after a lower September minimum extent.
2. Thin ice grows much faster than thick ice. Thus faster winter ice increase compensates for thinner ice after a strong melt season.
3. More open ocean leads to higher humidity and more extensive or thicker cloud cover over the Arctic Ocean in the summer. More extensive or thicker cloud cover in summer reflects more solar radiation and thus reduces summer ice melt.
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My wording is no doubt less than perfect for many of these. Some may be just plain wrong. Some I just made up! Maybe I should just find a good book or review article with such a list. Any suggestions?
If you think a proposed feedback is incorrect or wrongly stated, it would helpful to have that noted. But I'm not looking to start multiple debates about which feedbacks are most important.
I don't get a commission for each new proposed feedback, so there's no need to get heated. The planet is hot enough as it is. These are just suggested entries. There must be suppressive feedbacks missing from the list.
I just thought a list would be interesting because I keep finding out about feedbacks I had not previously been aware of.
