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uk.sci.weather (UK Weather) (uk.sci.weather) For the discussion of daily weather events, chiefly affecting the UK and adjacent parts of Europe, both past and predicted. The discussion is open to all, but contributions on a practical scientific level are encouraged. |
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#21
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On Saturday, 28 January 2017 21:56:04 UTC, John Hall wrote:
In message , Alastair writes This chart is a little ahead of the NSIDC one and you can see from it that the Arctic sea ice has begun to melt again. https://ads.nipr.ac.jp/vishop/#/extent If the amount of Arctic sea ice is reducing in JANUARY, even if it turns out to be only for a day or two, that seems remarkable and really brings it home just how far global warming has gone. It happened in 2012. http://nsidc.org/arcticseaicenews/ch...sea-ice-graph/ The sea ice etc. is chaotic, which makes it very difficult to predict. It is very difficult to work out what it is going to do until it has done it :-) -- John Hall "One can certainly imagine the myriad of uses for a hand-held iguana maker" Hobbes (the tiger, not the philosopher!) |
#22
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"John Hall" wrote in message ...
If the amount of Arctic sea ice is reducing in JANUARY, even if it turns out to be only for a day or two, that seems remarkable and really brings it home just how far global warming has gone. ====================== This is for extent, which AIUI is more liable to error, as a parameter rather than area but interesting nonetheless. But if you look at the NSIDC extent chart at: http://nsidc.org/arcticseaicenews/ you'll see that there was a also a brief net melt in November 2016 and certainly a stall if not a technical dip in December and again in mid-January. What seems to be concerning the experts more than the relatively low current area/extent values is that a substantial proportion of the arctic ice is thin; while this will certainly still contribute to the area/extent values as if it were traditional thicker ice, it will also be easier to melt out once the spring/summer thaw starts in earnest. So arctic ice _volume_ is potentially a more interesting parameter, though one tricky to estimate and not updated publicly on a daily basis AFAIK. So it will be interesting to see the PIOMAS end-January volume estimate when it hopefully gets released in around a week's time. |
#23
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On 29/01/2017 08:54, JohnD wrote:
"John Hall" wrote in message ... If the amount of Arctic sea ice is reducing in JANUARY, even if it turns out to be only for a day or two, that seems remarkable and really brings it home just how far global warming has gone. ====================== This is for extent, which AIUI is more liable to error, as a parameter rather than area but interesting nonetheless. But if you look at the NSIDC extent chart at: http://nsidc.org/arcticseaicenews/ you'll see that there was a also a brief net melt in November 2016 and certainly a stall if not a technical dip in December and again in mid-January. What seems to be concerning the experts more than the relatively low current area/extent values is that a substantial proportion of the arctic ice is thin; while this will certainly still contribute to the area/extent values as if it were traditional thicker ice, it will also be easier to melt out once the spring/summer thaw starts in earnest. So arctic ice _volume_ is potentially a more interesting parameter, though one tricky to estimate and not updated publicly on a daily basis AFAIK. So it will be interesting to see the PIOMAS end-January volume estimate when it hopefully gets released in around a week's time. The local retired polar oceanographer, living near me, seems to be most concerned about the lack of multiyear ice in the Arctic, ie lack of structural integrity. The lack of Antarctic sea-ice area is before Larsen C breaks off |
#24
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"N_Cook" wrote in message news
![]() The lack of Antarctic sea-ice area is before Larsen C breaks off Are you sure that the ice-shelf areas contribute to the overall sea ice figures? My impression was that they didn't - I guess on the basis that are (largely?) grounded ice fed by glaciers rather than floating sea ice. I thought that the 'land' area boundaries of Antarctica on the extent maps actually included the ice shelves. But ICBW and I'm sure someone here must know for sure. |
#25
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On 29/01/2017 09:24, JohnD wrote:
"N_Cook" wrote in message news ![]() The lack of Antarctic sea-ice area is before Larsen C breaks off Are you sure that the ice-shelf areas contribute to the overall sea ice figures? My impression was that they didn't - I guess on the basis that are (largely?) grounded ice fed by glaciers rather than floating sea ice. I thought that the 'land' area boundaries of Antarctica on the extent maps actually included the ice shelves. But ICBW and I'm sure someone here must know for sure. I've no knowledge on that, this is just my halfpennyworth. If the ice is over seawater and when it breaks off it forms an ice-berg, then classed as sea-ice I would have thought. Penetrating radar has long since defined the boundary of the land. |
#26
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"N_Cook" wrote in message news
![]() I've no knowledge on that, this is just my halfpennyworth. If the ice is over seawater and when it breaks off it forms an ice-berg, then classed as sea-ice I would have thought. Penetrating radar has long since defined the boundary of the land. ================ Yes, certainly, the true land boundary of the Antarctica is well known. But that's not to say that the ice-shelves are not added to the land boundary for the purpose of the sea ice maps. Take a look for example at the extent of the Ross ice shelf, as per: https://en.wikipedia.org/wiki/Ross_Ice_Shelf Then compare that to the current NSIDC map. The Ross sea ice looks to have very largely gone, yet there's no suggestion AFAIK that the Ross ice shelf is actively melting. So it's presumably still all there, yet not showing up on the NSIDC map. And the introductory notes to sea ice at eg: https://nsidc.org/cryosphere/seaice/index.html make a major distinction between sea ice and land-derived ice, eg: 'Sea ice is simply frozen ocean water. It forms, grows, and melts in the ocean. In contrast, icebergs, glaciers, ice sheets, and ice shelves all originate on land. ' 'The most basic difference is that sea ice forms from salty ocean water, whereas icebergs, glaciers, and lake ice form from fresh water or snow. Sea ice grows, forms, and melts strictly in the ocean. Glaciers are considered land ice, and icebergs are chunks of ice that break off of glaciers and fall into the ocean.' (Though this para doesn't specifically mention ice shelves, AIUI the shelves are made from glacier ice and so aren't sea-ice by definition.) |
#27
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In message ,
Alastair writes On Saturday, 28 January 2017 21:56:04 UTC, John Hall wrote: In message , Alastair writes This chart is a little ahead of the NSIDC one and you can see from it that the Arctic sea ice has begun to melt again. https://ads.nipr.ac.jp/vishop/#/extent If the amount of Arctic sea ice is reducing in JANUARY, even if it turns out to be only for a day or two, that seems remarkable and really brings it home just how far global warming has gone. It happened in 2012. http://nsidc.org/arcticseaicenews/ch...sea-ice-graph/ The sea ice etc. is chaotic, which makes it very difficult to predict. It is very difficult to work out what it is going to do until it has done it :-) I can see that its chaotic nature would make it likely that in any particular region it would reduce from time to time even in midwinter. But it still seems remarkable to me that, taken over the Arctic as a whole, the areas where the extent was reducing should be sufficient to outweigh the areas where it was increasing, even for a brief period. -- John Hall "One can certainly imagine the myriad of uses for a hand-held iguana maker" Hobbes (the tiger, not the philosopher!) |
#28
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On 28/01/2017 21:55, John Hall wrote:
In message , Alastair writes This chart is a little ahead of the NSIDC one and you can see from it that the Arctic sea ice has begun to melt again. https://ads.nipr.ac.jp/vishop/#/extent If the amount of Arctic sea ice is reducing in JANUARY, even if it turns out to be only for a day or two, that seems remarkable and really brings it home just how far global warming has gone. If it is reducing in January, surely that isn't directly related to the temperature, it should be well below freezing up there now. It is not something to do with the synoptics, maybe storminess leading to breakup and advection of sea ice (I haven't checked this out so am just speculating)? |
#29
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Change of title required as global sea-ice extent down to a new record
of 16.414 million sq km on 28 Jan 2017 using Chrctic NSIDC data |
#30
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"Adam Lea" wrote in message
... If it is reducing in January, surely that isn't directly related to the temperature, it should be well below freezing up there now. It is not something to do with the synoptics, maybe storminess leading to breakup and advection of sea ice (I haven't checked this out so am just speculating)? ========================== I think it's all of those things. There's a fairly detailed day by day commentary if you're interested on arctic sea ice forum at eg: https://forum.arctic-sea-ice.net/ind...1611.2250.html |
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