Coastal Sea Ice has a Major Influence on Deep Ocean Circulation

[wili]

http://universityofcalifornia.edu/news/formation-coastal-sea-ice-drives-ocean-circulation

An unprecedented analysis of North Pacific ocean circulation over the past 1.2 million years has found that sea ice formation in coastal regions is a key driver of deep ocean circulation, influencing climate on regional and global scales.

Coastal sea ice formation takes place on relatively small scales, however, and is not captured well in global climate models, according to scientists at the University of California, Santa Cruz, who conducted the study.

A paper on the new findings will be published in a future issue of the journal Paleoceanography and is currently available online.

“We have identified an important process that current global climate models don’t adequately capture. Coastal sea ice formation may be important to future climate change because the arctic and subarctic regions are warming at twice the rate of other parts of the world,” said first author Karla Knudson, a graduate student in Earth and planetary sciences at UC Santa Cruz.

This seemed like pretty big news, relevant to what we follow here, so worthy of its own thread.

[Neven]

How does that coastal sea ice (I presume they mean sea ice in the Bering and Okhotsk Seas, off the Alaskan and Chukotka) drive ocean circulation exactly?

Sorry, too busy to read the article. 

[ktonine]

It's thermohaline circulation.

When sea ice forms, it expels salt into the surrounding water, increasing the density of the water and causing it to sink, carrying oxygenated surface water into the depths. One result is a flow of cold deep water toward the equator and warm surface water toward the poles, and this "overturning circulation" plays a crucial role in moving heat around the globe.

What they seem to be saying that's new is that this process occurs in the North Pacific as well as the North Atlantic (most are familiar with the AMOC).

[Bruce Steele]

The article seemed straightforward to me. It compares deep water formation in the Bering Sea when glaciation has closed the Bering Strait to current times when it is open and intermediate water formation from the Sea of  Okhotsk takes over.
 North Pacific Intermediate Water is formed when coastal sea ice formation in the Sea of Okhotsk drives cold  saline water to the bottom where it flows out into the Pacific and mixes with the South flowing Oyashio Current. The Intermediate water formed then flows above the slower moving deep water and crosses the Pacific in about 30-50 years. These Intermediate waters upwell along the North American continent and are largely responsible for acidification events in the northern part of the California current during strong offshore wind events.
 The part of this article that shows Deep water formation during glacial ages ( when the Bering Strait closes) is the part that would drive a North Pacific MOC that doesn't occur in warm eras like the one we live in.
 I agree with Wili that this is important new information but how it would change climate models relevant to current conditions isn't so clear.     

[ChrisReynolds]

Thanks Wili, very useful.

[kingbum]

Just like if there is substantial coastal ice in Greenland driving down the temperatures in the North Atlantic and consequently pushing the Gulf Stream South near France and Spain instead of Scandinavia... I'm assuming there's a newly discovered process in the Pacific as well which makes sense why would this be unique to the Atlantic? Looks like the Bering Sea is more informative than once thought maybe