|
Post by dontgetoutmuch on Jul 21, 2014 15:06:23 GMT
Track the boatsLooks like they have set sail... Did you guys get a load of the crew? This will end badly.
|
|
|
Post by sigurdur on Jul 21, 2014 16:18:14 GMT
Some of us didn't realize that sigurdur! Your superior knowledge is of advantage to you in the "competition" Are you still confident of your low sea ice area by September? I still think my 3.3 might be about right Even using sea ice area we are still above 2013 as yet. The export of ice has been marginal this year, and the forecast looks like it won't increase. My 2.2 now looks to be pretty low. A change of pattern, which can still happen, could result in a blast of ice exported. With that said, time is running out to get to a 2.2 low so your 3.3 potentially is a lot closer.
|
|
|
Post by neilhamp on Jul 21, 2014 19:29:08 GMT
I am something of a sceptic regarding AGW. I would therefore be delighted if 2014 showed further recovery on 2013 This did occur in the previous low of 2007 to 2008 then 2009
|
|
|
Post by Ratty on Jul 21, 2014 21:35:12 GMT
That is why I chose area rather than extent. It is actually a bit more accurate in regards to Arctic Sea Ice. Unless sea ice is actually expanding, which would be one heck of a strange event at this time of year, the area should continue declining, but it may slow the decline. Is this what you mean, Sig .... I guess DMI's "icecover_current" means "area"?
|
|
|
Post by sigurdur on Jul 21, 2014 23:40:17 GMT
I will have to look at DMI. Cryosphere is the results of the new satellite.
You can have an actual increase in sea ice extent, 15 and 30% during the Arctic summer. The extent depends on the distribution of the ice. Example would be a washtub with ice stacked tightly in a corner. Shake the tub and places that had no ice will now have ice. The extent has increased but the actual area of the ice will still be the same.
|
|
|
Post by sigurdur on Jul 22, 2014 0:08:42 GMT
That is why I chose area rather than extent. It is actually a bit more accurate in regards to Arctic Sea Ice. Unless sea ice is actually expanding, which would be one heck of a strange event at this time of year, the area should continue declining, but it may slow the decline. Is this what you mean, Sig .... I guess DMI's "icecover_current" means "area"? Ratty: I looked and this is sea ice extent, not ice area.
|
|
|
Post by Ufasuperstorm on Jul 22, 2014 1:20:31 GMT
That is why I chose area rather than extent. It is actually a bit more accurate in regards to Arctic Sea Ice. Unless sea ice is actually expanding, which would be one heck of a strange event at this time of year, the area should continue declining, but it may slow the decline. Is this what you mean, Sig .... I guess DMI's "icecover_current" means "area"? Ratty, Please do not confuse 15 percent concentration with 30 percent concentration. The difference is due to each of the sea ice extent graphs having different thresholds for sea ice. The one that you posted is for ice concentrations higher then 30 percent are classified as sea ice. The other graph was ice concentrations higher then 15 percent are classified as sea ice. Neither has anything to do with area. Area, extent, and volume are different measures and give scientists slightly different information. It is also important everyone here understands the difference between extent, area, and volume. For example pretend you have a sponge. The extent is from the edge to all the other edges and all the space inside of it. The area would be where there is sponge only, not including any of the holes. This is why area is always a lower value then extent. Volume is a value calculated using ice density, snow cover thickness, air pressure, water salinity to eventually calculate the volume.
|
|
|
Post by sigurdur on Jul 22, 2014 2:53:34 GMT
Thanks ufasuperstorm. The sponge analogy was an excellent description.
|
|
|
Post by Ratty on Jul 22, 2014 6:06:45 GMT
Is this what you mean, Sig .... I guess DMI's "icecover_current" means "area"? Ratty, Please do not confuse 15 percent concentration with 30 percent concentration. The difference is due to each of the sea ice extent graphs having different thresholds for sea ice. The one that you posted is for ice concentrations higher then 30 percent are classified as sea ice. The other graph was ice concentrations higher then 15 percent are classified as sea ice. Neither has anything to do with area. Area, extent, and volume are different measures and give scientists slightly different information. It is also important everyone here understands the difference between extent, area, and volume. For example pretend you have a sponge. The extent is from the edge to all the other edges and all the space inside of it. The area would be where there is sponge only, not including any of the holes. This is why area is always a lower value then extent. Volume is a value calculated using ice density, snow cover thickness, air pressure, water salinity to eventually calculate the volume. Apologies in advance ufasuperstorm ..... now you will need to explain "concentrations" cf. area, extent and volume. Or, point me to a website with some simple explanations. I do (and did) understand the distinction between area and extent but "concentration" is new to me. DMI's use of "icecover" doesn't help at all but their chart is obviously a smaller area than NSIDC's 15% ice extent chart ( Area of ocean with at least 15% sea ice). Is the "concentration" in the DMI chart an indication that it is a measure of the Arctic with no visible water? Conversely, is NSIDC's chart showing scattered ice? Is volume a measure of ALL the ice, out to the extent?
|
|
|
Post by flearider on Jul 22, 2014 8:32:16 GMT
"concentration" I've always took is how dense the ice is ..how compact 1yr ice 2nd and so on .. ?
|
|
|
Post by Ratty on Jul 22, 2014 11:47:48 GMT
"concentration" I've always took is how dense the ice is ..how compact 1yr ice 2nd and so on .. ? Glad I'm raising this because there is so much jargon in the climate area, not much clarity and few remaining investigative journalists to delve into the subject (climate generally). Most of the MSM in this country takes the line of least resistance and reports the (alleged) consensus view, without comment or question.
|
|
|
Post by sigurdur on Jul 22, 2014 14:31:29 GMT
Ok. 1. Sea ice extent comes in two variations. 15% and 30%.
The 15% is based that within a sq kilometer there is at least 15% ice The 30% is based that within a sq kilometer there is at least 30% ice
Sea ice area measures the ice within each kilometer, adds it up and produces area. This is how much area would be total ice.
Until Cryostat sea ice area was a very dubious measurement. Melt ponds on top of ice would look like open water, when in fact there was ice below. The transponders on Cryostat are able to determine whether it is open water or ice covered water.
A storm during Arctic summer can produce an increase in sea ice extent because it will scatter the more dense ice. It would not produce more ice area, in fact, the result would prob be a somewhat rapid decrease in area as that would expose the ice flow edges to more open/warmer water.
That is why I used area. 10 years ago, I would not have chosen that metric, but with the advances in satellite readings it is now possible, and is a better metric of ice content in the Arctic.
|
|
|
Post by sigurdur on Jul 22, 2014 14:39:40 GMT
arctic.atmos.uiuc.edu/cryosphere/arctic.sea.ice.interactive.htmlOne can note that there is less short term variation in sea ice area because as the Arctic summer progresses, the ice melts. Kinda like having ice in a glass. The ice floating on top of the glass is slowly dissolving, and as it gets smaller you can see water between the cubes. You know the ice is melting, but looking at the top of the glass you also can see that 30% of the area has ice distributed in it. I hope this helps.
|
|
|
Post by sigurdur on Jul 22, 2014 14:42:09 GMT
Actual volume of ice has also become more certain because of Cryostat. Before this, it was modeled, and the error bars of the models were huge.
Volume doesn't equate to area, nor extent as the thickness of the ice can vary substantially when viewed only on the surface.
|
|
|
Post by sigurdur on Jul 22, 2014 14:46:51 GMT
|
|