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Author Topic: What's new in the Arctic ?  (Read 183075 times)

Glen Koehler

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Re: What's new in the Arctic ?
« Reply #600 on: January 07, 2021, 04:10:53 PM »
The end-game begins through the Nares Strait?

"Ice arches holding Arctic's 'last ice area' in place are at risk, researcher says"
https://phys.org/news/2021-01-ice-arches-arctic-area.html

Excerpts  -------
But recent research at the University of Toronto Mississauga suggests the last ice area may be in more peril than previously thought. In a recent paper published in the journal Nature Communications, Professor Kent Moore and his co-authors describe how this multi-year ice is at risk not just of melting in place, but of floating southward into warmer regions. This, in turn, would create an "ice deficit" and hasten the disappearance of the last ice area.

"The last ice area is losing ice mass at twice the rate of the entire Arctic," Moore says. "We realized this area may not be as stable as people think."

His most recent analysis of satellite data says the problem may be getting even worse. The arches along Nares Strait that historically have held the Last ice Area in place have become less stable, according to the study.

"The ice arches that usually develop at the northern and southern ends of Nares Strait play an important role in modulating the export of Arctic Ocean multi-year sea ice," he and his authors write.

Ice arches only form for part of the year. When they break up in the spring, ice moves more freely down the Nares Strait. And that breakup is happening sooner than in the past.

"Every year, the reduction in duration is about one week," (emphasis added by GK) Moore says. "They used to persist for about 200 days and now they're persisting for about 150 days. There's quite a remarkable reduction.

"We think that it's related to the fact the ice is just thinner and thinner ice is less stable."

More information: G. W. K. Moore et al. Anomalous collapses of Nares Strait ice arches leads to enhanced export of Arctic sea ice, Nature Communications (2021). DOI: 10.1038/s41467-020-20314-w

Glen Koehler

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Re: What's new in the Arctic ?
« Reply #601 on: January 26, 2021, 03:27:35 AM »
From:
Slater, T., Lawrence, I. R., Otosaka, I. N., Shepherd, A., Gourmelen, N., Jakob, L., Tepes, P., Gilbert, L., and Nienow, P.: Review article: Earth's ice imbalance, The Cryosphere, 15, 233–246, https://doi.org/10.5194/tc-15-233-2021, 2021.
https://tc.copernicus.org/articles/15/233/2021/tc-15-233-2021.pdf 

     "While the progressive retreat of Arctic sea ice has been driven by radiative forcing, this has been mediated in part by the increasing presence of open water (Perovich and Richter-Menge, 2009), and broader changes in oceanic conditions are expected to play an increasingly important role (Carmack et al., 2016)"

     But the at the end of the article they say this:  "Attributing Arctic sea ice decline and ice shelf calving to increased radiative forcing,..."
      I understand that they do this as a shortcut in a calculation of what portion of global glacier/ice sheet/sea ice loss is due to atmospheric vs. ocean warming.  But that seems like a pretty crude shortcut.  My understanding is that ocean warming is already a contributing factor to ASI loss, as they alluded to in the statement about open water "mediating" progressive ASI loss.

     RE: the table shown below comparing Gt/year ice loss between periods.  I find it odd that the amount of ASI loss in 2000s is higher than for the 2010s.  Even multiplying the 2010s number by 1.1 since it only accounts for 2010-2018 (missing 2019) gives a much smaller value of ca. 103 vs. the 384 for the 2000s.

    Wipneus' PIOMAS volume graph for Sept. mininum volume shows change from 2000 to 2009 of ca. 11 to 7 M km3, and ca. 7 to 4 for 2010 to 2019.   That is not directly relevant since the study used the winter (October -April) average ASI volume trend not the summer minimum trend for their ice loss measure.  But I don't see how the losses in 2000-2009 could so much exceed the 2010-2018 value.  And even the 1980s and 1990s rates of winter ASI loss are almost 1.5 and almost 3X higher than the extrapolated Gt/year for 2010s. 

    Even though it is measuring a different month of the year, I do not see why the Wipneus Sept minimum chart would show a consistent trend in losses while this study apparently finds a much lower rate of ASI loss in the 2010s. 

    Finally, they note that the energy used to melt ice only accounts for 3.2% of the net Earth energy imbalance.  While some has gone into the atmosphere and plants, 93% (other source) goes into ocean warming.  That hides the "damage" from us in the sense that heat buried in the ocean is not immediately apparent.  But the bad news is that the ocean has huge thermal inertia.
Once energy is stored there, it stays there for a very long time, essentially forever from a human perspective, and will continue to exert changes on ocean currents, atmosphere (and the weather), marine life, and the remaining ice.
« Last Edit: January 27, 2021, 02:46:03 PM by Glen Koehler »

kassy

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Re: What's new in the Arctic ?
« Reply #602 on: January 26, 2021, 04:34:22 PM »
Well the winter ice was thicker over all so there was more to melt out then.
Þetta minnismerki er til vitnis um að við vitum hvað er að gerast og hvað þarf að gera. Aðeins þú veist hvort við gerðum eitthvað.

Glen Koehler

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Re: What's new in the Arctic ?
« Reply #603 on: January 27, 2021, 02:47:42 PM »
   Yes, but there was also a lot more summer ice in the earlier decades, yet the PIOMAS volume (e.g. Wipneus chart) shows a steady rate of decline.  So why would winter (Oct-Apr) losses show a 2/3 reduction in loss rate for the most recent decade compared to prior decades, while September minimum losses continued to follow a consistent trend?
« Last Edit: January 27, 2021, 07:40:55 PM by Glen Koehler »

kassy

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Re: What's new in the Arctic ?
« Reply #604 on: January 27, 2021, 08:06:07 PM »
They are not so much winter losses as snapshots of the overall loss only taken in winter.

For more details we should take it to the When thread.
Þetta minnismerki er til vitnis um að við vitum hvað er að gerast og hvað þarf að gera. Aðeins þú veist hvort við gerðum eitthvað.