Ice Pie

I was prompted earlier to complete my previous post by an article in today’s Guardian which reported on “[n]ew research [that] does not question climate change is also melting ice in the Arctic, but finds wind patterns explain steep decline”.  The word “also” is confusing – you can hardly consider “climate change” to be entirely separate phenomenon from (changing) “wind patterns”.  I’m also a little confused as the paper by “Masayo Ogi, a scientist with the Japan Agency for Marine-Earth Science and Technology in Yokohama, and… colleagues… to be published in the journal Geophysical Research Letters” (presumably around now, 22/3/10) sounds strikingly similar to the one “led by Son Nghiem at NASA’s Jet Propulsion Laboratory” mentioned in January on a NYT blog, also “appearing this week [i.e. that of 13/1/10 when the blog entry was published] in Geophysical Research Letters”.

Anyway, the findings provide even more food for thought. The point is that:

“…winds have blown large amounts of Arctic ice south through the Fram Strait, which passes between Greenland and the Norwegian islands of Svalbard, and leads to the warmer waters of the north Atlantic. These winds have increased recently, which could help explain the apparent acceleration in ice loss.

‘Wind-induced, year-to-year differences in the rate of flow of ice toward and through Fram Strait play an important role in modulating September sea ice extent on a year-to-year basis,’ the scientists say. ‘A trend toward an increased wind-induced rate of flow has contributed to the decline in the areal coverage of Arctic summer sea ice.’

Ogi said this was the first time the Arctic winds have been analysed in such a way.

‘Both winter and summer winds could blow ice out of the Arctic [through] the Fram Strait during 1979-2009,’ she said.”

First, the idea is compatible with a natural Arctic sea-ice cycle.  In cold Northern Hemisphere (NH) winters – which, to recap, I suggest are more likely to occur when the Arctic sea-ice extent is less than usual at the end of summer – air pressure over Greenland (and other northern land areas) is relatively higher than usual.  The resulting anticyclonic winds would tend to drive ice down the east Greenland coast.  Once the trend reverses, not only would more ice form in the Arctic, the weather-patterns would also change and less ice would be blown out of the Arctic through the Fram Strait (east of N Greenland).  So the Atlantic Multi-decadal Oscillation (AMO) would be expected to include a see-saw in sea-ice to the west (Labrador Sea) and east of Greenland.  Maybe someone should check the history books.

Second, all this ice flowing (or should that be “floeing”?!) into the North Atlantic (NA) is a negative feedback.  It will contribute towards NA cooling, cutting off the flow of warm water into the Arctic, reducing ice melt.

Third, it might be worth noting that the mechanism involves the removal from the Arctic of fresh water (in the form of ice).   It’s conceivable that this could be important, as the saltier the surface waters in the Arctic, the colder the water will get before it freezes.  That is, the sea can lose more heat to the atmosphere, or by radiating it away, before freezing over and insulating the waters below from the atmosphere. Likely, more cold deep saline water will form too, driving the thermo-haline circulation (THC).  Maybe someone should do some maths to see how significant this effect is.