ARCTIC SEA-ICE –May Gale Blasts MOSAiC Expedition–

The past winter saw a surprising number of powerful lows cross Barents Sea into Kara Sea, with the north winds behind these gales pulling sea-ice south around Svalbard. The most recent gale took a more traditional route, hooking back west in a retrograde manner and passing right over Svalbard.

The MOSAiC Expedition, in the sea-ice about a third of the way to the Pole from Svalbard, experienced winds of 83 km/hr north of the gale, as the sea-ice accelerated from a nearly stationary drift to a drift  of over a kilometer an hour for a while. The bow-radar on the Polarstern showed a lead open and close, but not a great break-up of sea-ice. The sea-ice, which had been showing a slow drift southeast, was jerked west-southwest.

The MOSAiC Expedition, north of all the Barent Sea storms, has seen sea-ice in the Transpolar Drift move about twice as fast as usual. The hook to the southeast  was unusual, and perpendicular to the drift the Fram saw, New Years to Mayday, in 1896.

The recent jerk to the west-southwest is more in line with the Fram’s Track. It will be interesting to study the condition of the sea-ice, once the weather clears and the satellite view improves. Currently it looks like the gale tore the sea-ice from the north coast of Svalbard.

What I wonder about is how much the sea-ice was compressed between Svalbard and the MOSAiC expedition. The Polarstern is suppose to head south towards Svalbard to be resupplied, and what they desire for such a journey is leads, and not pressure ridges.

There is an excellent video of part of the Russian icebreaker Kapitan Dranitsyn”s trip south from the MOSAiC site to port, showing how it has to back up and then ram to get through even ordinary sea-ice, yet has a far easier time once it finds leads skimmed with baby-ice.

In all, the journey of the Kapitan Dranitsyn from the MOSAiC site to port took three and a half weeks. The ship made it about halfway back to port in the thick sea-ice, and then was met by the Russian icebreaker Admiral Makarov, that refueled it. I think it took four days to complete the refueling. They then proceeded to the edge of the sea-ice in Barents Sea, but had to wait before venturing out into the open water because a gale was raging and the seas were too high. (I guess icebreakers are not designed for ocean storms.) They had to wait a week for the waves to subside under fifteen feet, but the MOSAiC scientists aboard got to observe how sea-ice fractures under the duress of huge swells. When the gale subsided they rushed across Barents Sea and two days later safely arrived in Tromso. (Likely some of the scientists had further adventures getting back to their home countries through the travel-bans of the Pandemic.)

It will be interesting to see what the Polarstern experiences, heading south.

The storm brought milder air over the arctic sea, including the year’s first patch of above-freezing air north of the Laptev Sea.

The sea-ice “extent graph” shows the typical decline for this time of recent years:

Interestingly, the “volume” graph hasn’t fallen much, suggesting much of the sea-ice lost on the “extent” graph is baby-ice at the periphery, without much bulk to it.

Stay tuned.

 

 

ARCTIC SEA ICE –Icebreaker Rescued–

The Kapitan Dranitsyn left the MOSAiC ice floe with the team of leg 2 on 4 March and met Admiral Makarov at 84°48′ North and 42°35′ East on Saturday, 14 March. (Photo Credit Steffen Graupner)

This episode is interesting because it demonstrates the sea-ice is thicker than exspected up towards the Pole. The Kapitan Dranitsyn, in successfully resupplying the MOSAiC expedition, was forced to plow through thick sea-ice at times, seeking the thinner refrozen leads, and consumed far more fuel than expected. It did not have enough fuel to plow its way back to Russia. (One does not want the gas gauge too close to empty, up on the Arctic Sea, for the fuel must be used for heating as well as powering the engines. At some point one must chose between powering forward and avoiding freezing to death.)

When it became apparent Kapitan Dranitsyn did not have enough fuel to make it back the Admiral Makarov was sent north to refuel it. After the ships met refueling took three days. I am curious how they handle diesel at temperatures when it tends to jell, (and it becomes obvious why the Russians turned to nuclear powered icebreakers.)

Rather than poking fun at the Russian’s struggles with the especially thick ice and especially cold temperatures, I tend to marvel that they can travel through the Arctic Sea in the dead of winter. The United States has no such ships nor such experience. I’m not sure of the state of the “Space Race”, but Russia is winning the Ice Race.

The MOSAiC site was hit by strong winds from another big storm in Barents Sea, and a lead formed that intersected the ship.

This crack should be handy, for they have been trying to study the gases released from the water in such leads, which involved dangerous hikes far from the ship. Now they hardly have to leave the Polarstern at all. However I wonder what stresses this puts on the ship’s hull.

Likely some Alarmists will suggest such a crack proves the sea-ice is thinner, but such leads open and then clap shut (forming pressure ridges) all over the Arctic Sea every winter, and by spring it is hard to find flat areas of sea-ice large enough for blue-ice airstrips.

The storm that stressed the sea-ice by the Polarstern did bring some slightly warmer air north, but temperatures remain cold up there. The coldest temperatures have swung around to the Atlantic side, and though a bit above the 1958-2002 mean overall, they remain colder than they’ve been in recent years as a zonal flow keeps the cold locked in the north.

The “extent” remains the highest in five years.

Stay Tuned.

ARCTIC SEA ICE –Icebreaker Trapped Resupplying MOASiC–

In my last post I mentioned that the Russian icebreaker  Kapitan Dranitsyn had to battle thick sea-ice to resupply the Polarstern at the MOSAiC site. Contact was successful, and cranes began to  unload and load supplies that were hauled by tractor between the two ships.

A fresh crew of scientists relieved the crew that has been working there.

With temperatures down around -30ºC, the open water in the wake of the Kapitan Dranitsyn froze over swiftly. Men could walk on the new ice within 24 hours.

By the time the transfer of men and supplies was complete the ship was frozen so fast it could not extract itself. The news is now that the Russians are sending a second icebreaker, the Admiral Makarov, to help the first icebreaker free itself. (Note the twilight in the above picture. The are located close enough to the Pole to see a very swift transition from noontime night to midnight day. Currently it is dark at midnight, but the twilight is bright enough at noon to read by. In around a week the sun will peek over the horizon, and a few weeks more will see the daylight become constant. But the chilly sun remains so low that no thawing occurs until the end of April.)

Despite the ice trapping the icebreaker, it is important to remember we are talking about sea-ice, a mass of ice in constant motion with enough “leads” (cracks) to allow seals to breathe and be seen hunting arctic cod, by the MOSAiC underwater cameras. Sea-ice is by no means stable. The Polarstern radar recently saw a lead open roughly a mile from the ship.

And the infrared view of the Pole shows plenty of cracks in the sea-ice,

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In other words, sea-ice is not the same thing as the gigantic icebergs that make life interesting for fishermen in Newfoundland, icebergs that are so vast that they can run aground in water 300 feet deep.

These giant, awesome bergs calve off glaciers, (largely Greenland’s), and, while they have been seen in the Arctic Ocean, they usually head south down either side of Greenland, and are rare up north. For the most part the sea-ice affecting the icebreakers is thin in comparison, roughly six feet thick.

The problem is that, besides cracking apart, which is helpful to icebreakers, the ice claps back together again. In such cases the baby-ice which swiftly forms in the open water, (as we saw in the wake of the Kapitan Dranitsyn), has little hope of resisting the compression it undergoes; even if it is two feet thick it is clamped in the jaws of ice at least three times as thick, which has the power of wind pressing across miles and miles of fetch. Consequently the new ice in leads crumples up like eggshells between elephants, and what was open water on Monday may become a pressure ridge of crumbled slabs of ice by Friday. And, because this process goes on all winter long, the surface of the Arctic Sea is far from smooth. There are smooth areas, basically big slabs, but finding a smooth area large enough for the yearly Barneo blue-ice airstrip often involves a considerable search.

Considering the sea-ice is constantly tortured and contorted, the “thickness” maps portray an average, for in fact the ice can vary between open water and a towering pressure ridge in a hundred yards. (This was made visual back in the days we had cameras on buoys bobbing about the Pole.) Because both pressure ridges and leads are often too narrow to be seen by satellite, and also because how numerous they are varies a lot between stormy years and calm years, a certain amount of guess-work (also called “modelling”) goes into the creation of “thickness” maps…..which in turn leads to disagreements. For example the NRL map can show ice six feet thick

Whereas the DMI map shows sea-ice twelve feet thick:

These disagreements suggest the captains of icebreakers face uncertainty, as they face the sea-ice.  Not only are the captain’s initial maps to some degree “modeled”, but the circumstances they are sailing into are in constant flux. Though their radar may show an open lead ahead, a shift in the winds may turn that lead into a pressure ridge in a mere hour.

One then is led to wonder why these icebreakers are not ever crushed like a nut in a nutcracker. The compression involved when wind-shear creates two masses of sea-ice converging is hard to imagine. We are talking about fifty miles of ice colliding headlong with fifty miles of ice; even sea-ice nine feet thick can buckle, creating the arctic’s biggest pressure ridges, thirty feet high and (because nine tenths of an iceberg is under water) with “keels” extending downwards 270 feet. A 1880’s ship like the Jeanette, with a greatly reinforced hull, might survive 21 months clamped in sea-ice, but it stood little chance when the sea-ice concentrated its squeeze. (Descriptions of the moaning noise the Jeanette made as it went down are amazing.) Therefore men learned to structure hulls in a manner that caused squeezing from the side to lift the ships upward, rather than crushing inward. Icebreakers utilize such uplift, as the entire ship rides up and over the ice, which is then crushed down and broken by the sheer weight of the ship.

The Russian icebreakers are huge. The Kapitan Dranitsyn has seven stories of windows above the main deck. Let’s look at the picture again:

Besides riding up over the ice moving forward, such ships are designed to ride over ice when moving astern. When the ice is especially thick they can back up and plow forward repetitively, crunching the ice downwards and making their way to where radar indicates a lead may provide an easier path.

The fact Kapitan Dranitsyn requires help indicates, to me at least, that the sea-ice is especially thick in the Central Arctic this year.

Stay tuned.