Wintertime Arctic sea ice growth slows long-term decline: NASA

Posted: December 7, 2018 by oldbrew in Natural Variation, research, sea ice
Tags: ,

Arctic sea ice [image credit: cbc.ca]


Yes, it does say ‘slows’. There’s some rather convoluted logic about the present and future of Arctic sea ice going on here. Good luck to readers who think they can unravel it. But NASA does have to concede there’s a winter negative feedback going on, while doing its best to downplay possible consequences so as to keep the usual warming obsessions afloat.

New NASA research has found that increases in the rate at which Arctic sea ice grows in the winter may have partially slowed down the decline of the Arctic sea ice cover.

As temperatures in the Arctic have warmed at double the pace of the rest of the planet, the expanse of frozen seawater that blankets the Arctic Ocean and neighboring seas has shrunk and thinned over the past three decades.

The end-of-summer Arctic sea ice extent has almost halved since the early 1980s. A recent NASA study found that since 1958, the Arctic sea ice cover has lost on average around two-thirds of its thickness and now 70 percent of the sea ice cap is made of seasonal ice, or ice that forms and melts within a single year.

But at the same time that sea ice is vanishing quicker than it has ever been observed in the satellite record, it is also thickening at a faster rate during winter. This increase in growth rate might last for decades, according to a new study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.

This does not mean that the ice cover is recovering, though. Just delaying its demise.

“This increase in the amount of sea ice growing in winter doesn’t overcome the large increase in melting we’ve observed in recent decades,” said Alek Petty, a sea ice scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland and lead author of the study. “Overall, thickness is decreasing. Arctic sea ice is still very much in decline across all seasons and is projected to continue its decline over the coming decades. ”

Petty and his team used climate models and observations of sea ice thickness from the European Space Agency’s CryoSat-2 satellite to explore sea ice growth variability across the Arctic. The climate model results compared well both with CryoSat-2’s measurements and the results of another commonly used Arctic sea ice model, giving the authors confidence in the climate model’s ability to capture Arctic sea ice variability.

“The global climate model seems to do a good job of capturing the Arctic sea ice state and shows that most of the thickness change in the central Arctic is from thermodynamics, that is, ice formation and ice melt, although around the Arctic sea ice edge dynamics, which is ice transport, can play a bigger role,” Petty said.

These model simulations showed that in the 1980s, when Arctic sea ice was on average 6.6 feet (2 meters) thick in October, about 3.3 extra feet (1 meter) of ice would form over the winter.

That rate of growth has increased and may continue to do so for several more decades in some regions of the Arctic; in the coming decades, we could have an ice pack that would on average be only around 3.3 feet thick in October but could experience up to 5 feet (1.52 meters) of ice growth over the winter.

It seems counterintuitive: how does a weakening ice cover manage to grow at a faster rate during the winter than it did when the Arctic was colder, and the ice was thicker and stronger?

The answer has to do with the fact that sea ice thickens primarily from below, as the seawater under the ice freezes. If the sea ice layer floating over the ocean thins, the upper ocean is less insulated from the very cold Arctic winter atmosphere. That lowers ocean temperatures and builds more ice from below.

Continued here.

Comments
  1. oldbrew says:

    The answer has to do with the fact that sea ice thickens primarily from below, as the seawater under the ice freezes. If the sea ice layer floating over the ocean thins, the upper ocean is less insulated from the very cold Arctic winter atmosphere. That lowers ocean temperatures and builds more ice from below.

    Are they trying to claim the atmosphere makes the sea colder, when it already contains 3-6 feet or so of ice? Bearing in mind we keep being told the Arctic atmosphere is warming at some ridiculous rate compared to anywhere else, does any of that make sense? :/

  2. JB says:

    The temperature slope at the onset of the Emian was negative, and dropped quite rapidly after ~10Kyrs. With the onset of the Holocene its been a little flatter, but the trend has still been negative. Maybe in my grandchildren’s lifetime we’ll know if the sudden negative slope repeats. I’ll just be happy to get through the coming winters being able to start my diesels. The Arctic can take care of itself.

  3. Ice free oceans lose heat to the atmosphere during winter (and indeed most of the year) in the Arctic. In other words, the world is losing heat to space.

    Some of us have been arguing this for years!

    As for the claim that “sea ice is vanishing quicker than it has ever been observed in the satellite record, ” (in summer) we can file that in the “Arctic myths ” file.

    In reality, summer sea ice extent has been essentially unchanged in the last decade:

    http://ocean.dmi.dk/arctic/icecover_30y.uk.php

    And thickness has grown:

    https://notalotofpeopleknowthat.wordpress.com/2018/12/05/arctic-sea-ices-rapid-growth-in-november/

  4. ivan says:

    It would appear they are the victims of their own models. I very much doubt that any of the models have been audited and as the special exemptions have been piled on special conditions It wouldn’t be at all surprising if a square root of minus 1 has got in there somewhere.

    Why they rely on unvalidated models to come our with such obvious incorrect statements and expect anyone to believe them I don’t know. It would help if they applied the KISS principle to all their work – but then it wouldn’t follow the dogma of the UN church of climatology.

  5. oldbrew says:

    Rapid melting fail…

    GREENLAND ICE SHEET SIXTH HIGHEST ON RECORD
    Date: 07/12/18 Polar Portal Season Report 2018

    In 2018, Greenland’s total surface mass budget (SMB) is almost 150bn tonnes above the average for 1981-2010, ranking as sixth highest on record.
    . . .
    Although the total SMB for the 2016-2017 and 2017-2018 seasons are similar, development during the two seasons has been very different. Last year, the season began by gaining a lot of mass during the winter, whilst the development in SMB from the summer onwards reflected the long-term average. During the 2017-2018 season, SMB remained in line with the average from 1981-2010 until the summer, after which the development in SMB was higher than average.

    https://www.thegwpf.com/greenland-ice-sheet-sixth-highest-on-record/

  6. Phoenix44 says:

    To state the obvious, the more that melts, the more that can refreeze. The Arctic has a “peak ice” amount. If none of that melts, then the following winter there will be no new ice. If lots melts, then lots can refreeze.

    Thus there are “increases in the rate of sea ice growth in winter” whenever there are increases in the loss of sea-ice in the summer. Why the obvious needed new research and models is beyond me.

  7. Bloke down the pub says:

    ‘ NASA does have to concede there’s a winter negative feedback going on,’
    Almost from its beginnings, cagw theory has relied on the so called tipping points to create the fear necessary to sustain it. These depend on positive feedbacks and the melting of Arctic sea ice was one of the big ones, based on the idea that sunlight penetrates water more easily than it does ice. Unfortunately for them, they’d ignored two major flaws in their argument. Firstly, at the angles of incidence that the sunlight hits the surface at high latitudes, the amount of energy absorbed by water can be as low as that absorbed by ice. Secondly, for most of the year, the sun doesn’t shine at all. This combined with the fact, as the article acknowledges, that open water releases more energy than when covered in ice, means that the feedbacks are net negative.

  8. craigm350 says:

    Reblogged this on WeatherAction News and commented:

  9. oldbrew says:

    NASA – Chilly November in North America
    https://earthobservatory.nasa.gov/images/144342/chilly-november-in-north-america

    Except west of the Rockies and southern parts of Florida…

  10. Andrew Gray says:

    I seem to remember that all of the ice was supposed to have melted by around 2015 according to the experts.

  11. jim hogg says:

    The explanation supplied seems pretty clear: ” If the sea ice layer floating over the ocean thins, the upper ocean is less insulated from the very cold Arctic winter atmosphere. That lowers ocean temperatures and builds more ice from below.”