ARCTIC SEA-ICE –Over the Top–

Of the many variables affecting the creation, movement and dispersal of sea-ice, the super-storms of the northern Pacific and Atlantic have recently grabbed my attention, perhaps because the storm that made headlines off the coast of California was unusually far south, and made me wonder if unusual things were occurring elsewhere.

Not that there is much that is usual about “ordinary” super-storms. They do not get much press, because they largely live and die far from where most people live, but they are well worth watching, for they are more powerful than hurricanes and typhoons in their totality, though they lack the ferocious winds of a tropical storm’s central eye-wall.

They are strongest when the contrast between arctic air and the warm waters brought north by the Gulf Stream in the Atlantic and the Kuroshio System in the Pacific is at its greatest. They can grow with shocking speed, called “bombogenesis” by some, and sometimes fill and vanish nearly as rapidly, while other times they and their closely associated secondary and tertiary developments wobble about as features for weeks.

Because the Pacific is larger than the Atlantic, and the Siberian tundra creates crueler cold than Canada, you might think the Pacific super-storms would be larger, but in fact the Atlantic storms hold the records for lowest pressures. In some ways this makes sense, because the clash between cold and warm is crowded into a smaller area. In any case, such massive storms influence the currents and winds entering and departing the Arctic Ocean, and in this regard the Atlantic has greater power than the Pacific, at greater depths. In fact Bering Strait is so shallow that it dries up every ice age, and most water that is chilled and sinks in the Arctic departs via a deeper channel through Fram Strait. But it is the shallow currents bringing warmer water into the arctic which are most affected by the churning of super-storms, and are what originally drew my attention away from the sea-ice, southward to the storms.

One fascinating current is the WSC, which brings warm and saltier water into the Arctic equation through the east side of Fram Strait. It is complex because its warmth makes it more buoyant than colder water at the same time as its salinity makes it less buoyant than fresher water. Therefore, as it cools, it arrives at a point where it becomes less buoyant than the sea it is entering, and at that point it stops riding atop the sea, and takes a shallow dive, sliding beneath the arctic waters like a playing card sliding in to a deck. It can be followed as a submerged current a considerable distance, all the way around the Pole, even to where it exits on the west side of Fram Strait, though it is subjected to a number of variables which can change its course and even threaten its existence. It is a difficult task for scientists to measure its whereabouts because in some ways it is like attempting to follow something that wanders like an upper air jet stream, but you can’t measure it with a weather balloon, and instead have to drill through thick ice while looking over your shoulder for 1500 pound bears. Data is scarcer than most would like, and “funding is needed”. But one variable which effects the WSC is every, single superstorm that blows up in the Atlantic.

The WSC is fed by a northern tendril of the Gulf Stream which in effect bounces off Norway and proceeds north-northwest to Svalbard. If a super-storm is to the west southerly winds hurry this current on its way, but if the super-storm is to the east its northerly winds balk the current, and also chill it. This can make a considerable difference in the nature of the current as it reaches Fram Strait, and can cause the current to take its dive earlier or later than usual. Without measurements, one indication of where the current is taking its dive is where the sea-ice at the surface melts. When the WSC is at the surface the sea-ice melts away with a rapidity which astonishes me.

However all sorts of other variables need to be kept in mind. For example, melting the sea-ice adds cold water to the WSC which reduces its temperature, and also its salinity. Also the current is drawn north not merely by powers pushing from behind, but also it is sucked north by the fact polar water is sinking and water must come north to replace it. Varying such pushing and pulling will also alter the current, which affects the sea-ice. As is often the case with meteorology, if you focus on one thing you are likely missing another; (hopefully it is not a 1500 pound bear.)

When I last posted about sea-ice a powerful high pressure lay just south of the Laptev Sea, while the remnants of one super-storm dissipated in Barents Sea as a second super-storm exploded in Denmark Strait between Iceland and Greenland. Cold air was being recycled from west Siberia to east Siberia, creating a pool of air so cold records were set in places, as a second, smaller pool developed over the Canadian Archipelago.

In terms of the movement of sea-ice, the most noticeable feature (to me) was the divergence of isobars towards the Pole, with some heading south towards Fram Strait and some continuing across the Pole towards the Central Arctic, which created a split and some interesting leads of open water (which swiftly froze over). Also we noted the export of coastal sea-ice was largely from the Kara Sea, with the Laptev Sea (usually the largest exporter) relatively calm, and the high pressure actually rotating around and crushing ice up against the coast of the East Siberian Sea.

Four days later the situation had changed. The super-storm off the coast of Greenland retained its strength and wobbled east to become a Barents Sea Blaster.

This movement of a super-storm tends to drive south winds up into Barents Sea, compressing the sea-ice and crushing the edge northwards, while north winds howl down through Fram Strait bringing sea-ice south along the east coast of Greenland. But the divergance persists, and a cross-polar-flow developed from Siberia to Canada. Canada has quite enough cold air and doesn’t need imports.

The warm air shows up as a spike in the polar temperature graph, but the heat is swiftly lost to the endless night.

The crushing of sea-ice north in Barents Sea may at least partially explain the flattening of the sea-ice extent graph, when it usually continues to slowly rise in January.

The south winds eventually transported warmer than normal air into western Russia, as the rest of Russia remained below normal.

It is important to remember that, while the anomalies look red hot or even white hot, fifteen degrees above normal is still frigid when “normal ” is minus thirty. What passes for “warm” in Siberia is nothing I want to see crossing the Pole and heading my way. However the pattern persisted. Three days later saw the Barent Sea Blaster weakening in the Kara Sea, but a new superstorm brewing up in its wake down in Denmark Strait, and the cross polar flow continuing to transport Eurasian cold to North America. My only hope was that a powerful Aleutian super-storm might press north from the Pacific, create a counter cross-polar-flow, and blow all that sub-zero air back to Russia where it belongs.

The cross polar flow, and bit of a counter cross-polar-flow close to Bering Strait, were definitely effecting the sea-ice. For one thing, polynyas formed on the north coast of the Laptev Sea for the first time all winter, even as air below minus forty poured north, freezing the polynyas over in a matter of hours. (In the map below lilac to white indicates the thin ice on leads and polynyas, while the dark blue and very light blue indicates the pressure ridges, which were formerly jumbled up against the shore, being pushed out to sea. Some are over six feet thick, and are handy tracking devises that show how the sea-ice is moving, as winter progresses.)

The counter cross-polar flow has been interesting to watch, for it has robbed a surprising amount of sea-ice from the northwest coast of Alaska and crushed it against Wrangle island and the northeast coast of Siberia. (West of there, along 160 E, is a thick tendril of multi-year-ice reaching towards the Pole which will be interesting to watch.)

Lastly, all the sea-ice flushed south through Fram Strait and down the east coast of Greenland is doing something relatively rare. It is attempting to create an ice-bridge across Denmark Strait between Greenland and Iceland.

However I am not as interested in the movement of the sea-ice as I am in the transport of Siberian air over the top to Canada. I look to today’s map, hoping to see it stop…

Alas. No such luck. The storm which was in Denmark Strait has crossed to be a Barent Sea Blaster, and, while it (and its secondary) my not qualify as a super-storm, it does keep the flow going from Eurasia to Canada. Furthermore, that big blob of high pressure has high pressure because it is very cold, and cold air sinks, and presses down, making pressures higher. Let’s see how cold it is:

That is -30 degree air, (-22 degrees Fahrenheit). It is moving over a sea of water above freezing, so the water is warming it, or it is chilling the water, but in any case it is not getting colder…until…it gets on shore in Canada. Canada can home-grow its own cold, for even below the arctic circle the sun is very low at noon, the days are short, and during the long, starry nights the snow-covered ground loses heat you’d doubt could even exist in such a wintery landscape to outer space, and the air will drop to that magic number -40, which is the only time Celsius and Fahrenheit ever agree about anything. And then…

…And then, just south of Canada, is me. But it can’t possibly come this far. We’ve had the nicest January. I can walk outdoors after dark without a scarf. Even the tiny birds, which cold can kill in minutes if they don’t flit about with amazing care, avoiding wind and shadows, have been fearless. And last time I checked the long range forecast I saw no….but those computer models have a hard time seeing cold air, because it presses down so flat it sneaks beneath their radar. Let me check again.

Oh, bleep. There it is, next Saturday.

(The high temperature of 6 translates to -14.4 Celsius, and the low temperature of -14 translates to -25.6.)

The computer could be wrong, for it is still six days away. Or it could be worse; when cold air like that dives this far south it can generate a super-storm off our coast and bury us. It will be interesting to watch as it develops, but, as others look west for our next storm, it does demonstrate a reason I watch the Pole and look for things coming “over the top”.

Stay tuned.


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