Happy New Year 2024 (and sorry for the forum being offline some hours) /DM
Right now it's uncertain if 2019's lead in extent will be enough to stay ahead of 2012 because of huge August melt caused by the 2012 GAC. Average melt won't suffice for the record, but then again there hasn't been much average melt this season.To look this from another perspective, if an event comparable to GAC occurred also this year, 2019 would take the record easily. The consensus here seems to be that ice is badly enough preconditioned to make this possible.
Does anybody know how common this wave action is coming out of the North end of the Nares?Windy screenshot for Wednesday two days out.
unihamburg amsr2-uhh, jul28 overlaid onto more detailed bathymetry
Quote from: uniquorn on July 29, 2019, 01:59:41 PMunihamburg amsr2-uhh, jul28 overlaid onto more detailed bathymetryOutstanding. Nothing like a picture to demonstrate the correlation between ocean depth and ice retention.
Very interesting observation regarding the correlation between SST and ocean depth.Looking at SST progression from various points on the Pacific side, there is one region where the >0C SST's are extending as far north as 76C. Elsewhere it is not extending beyond 74C. Cross checking vs. a bathymetry map (at geology.com) reveals that the region in question sits above the Chuchki Plateau, a narrow strip of much shallower (min depth ~ 250m) ocean floor ridge that extends from N. Alaska out to ~ 79N before dropping off a cliff. It will be interesting to see how the Pacific SST's correlate to the contours of the ocean floor going forward. This has implications for future projections of sea ice decline.
unihamburg amsr2-uhh, jul28 overlaid onto more detailed bathymetry. amsr2 0% concentration, usually dark blue, has been set to fully transparent to allow bathymetric features to show through. This does reduce the impact of some open water areas (eg CAA/CAB crack) but we are mostly familiar with these by now.click to run. edit: changed animation orderno scale yet for bathy
The momentum flux from the atmosphere into the ocean (also known as ocean surface stress) depends on various factors such as wind speed, surface layer stability, surface roughness, and sea ice conditions. Roughness changes in response to changing ocean surface waves and variations in the geometry of ice floes and ridges. Three regimes characterize how sea ice moderates momentum transfer into the Arctic Ocean: 1. At very high ice concentrations, near 100%, the pack ice is so compact that it barely responds to the wind forcing and hence also shields the ocean from the wind. 2. Slightly lower ice concentrations, about 80-90%, allow the ice to drift freely with the wind as pressure within the ice pack is reduced to a minimum, while floe edges and ridges provide high drag (See Figure 1). We refer to this as an "optimal ice concentration", because ocean surface stress is maximal in this case -- as illustrated in the graph of ocean surface stress as a function of sea ice concentration derived from Pan-Arctic Ice Ocean Modeling and Assimilation System1 (PIOMAS) output (See Figure 2). 3. For still lower ice concentrations, stresses decline because open water—even with surface waves—is generally smoother than pack ice.
a shrinking summer sea ice extent means less momentum flux into the ocean in this season. How is that? In the 1980s and 1990s most of the Arctic Ocean featured high ice concentrations, even in summer, with an average close to the 80-90% optimum. In recent years however, vast areas of open water have reduced the mean ice concentration below this optimum, which results in an overall ocean stress decrease at a small but significant rate in summer.What does the future hold? The area of high momentum flux (See green in Figure 3a) is shrinking toward Greenland as sea ice continues to retreat. Further, an expanding summer season with increasingly less ice coverage might steepen the negative ocean stress trend and eventually even reverse the positive trends in spring and fall. But this assumes that wind forcing and ocean surface waves do not grow, an assumption that might prove incorrect in a changing climate. This illustrates the fascinating interplay between opposing forces that will determine the magnitude of Arctic Ocean currents in the future.
Our analysis indicates that sea ice in free-drift amplifies the momentum transfer from the atmosphere into the ocean, which contradicts the general perception that sea ice damps the atmosphere-ocean exchange.On annual average, most momentum is transferred at an ice concentration of 85%.On the seasonal scale, sea ice conditions are optimal for maximal momentum flux into the ocean twice a year, in spring and fall. However, wind speeds are much higher in fall
Quote from: Rich on July 29, 2019, 04:05:09 PMQuote from: uniquorn on July 29, 2019, 01:59:41 PMunihamburg amsr2-uhh, jul28 overlaid onto more detailed bathymetryOutstanding. Nothing like a picture to demonstrate the correlation between ocean depth and ice retention. Thanks for the compliment (if it is one) but I don't agree with your interpretation. Both beaufort and laptev/cab (laptev bite) have had large areas of open water over deep ocean in recent years. It's highly likely the laptev bite will open up significantly over the next month.Last year some of the ess arm never melted out over shallow water.Please do more research, less posting.
This post started from the ice-drift map (latest attached)
All that ice being exported to the Beaufort will be facing some heavy wave action. Windy screen shot from 5 days out on Friday.
IMHO the one thing 2019 was missing to get real low
Quote from: gerontocrat on July 29, 2019, 04:43:04 PMThis post started from the ice-drift map (latest attached)In other news, Wip's NSIDC 25 km area continues to bottom, unlike virtually every other metric. A sign of things to come, or just an outlier? Conversely, UH CAB area (Wip's definition) is in freefall and leads every other year including 2012. Will it slow in the next week or so like it did every other year? Very interesting times...
That overlaid bathymetry map shows the impacts of the subduction of heat in the Beaufort sea and the Nansen basin. The "Atlantification" of the Nansen basin is one of the major changes that has been taking place in the Arctic over the past 15 years. The new and very disturbing thing we're seeing this summer is the collapse of thick ice north of Ellesmere Island and in the Lincoln sea. I've looked on Worldview back as far as I could go and this summer is far worse around Ellesmere than any other year. It's hard to predict what this area will look like in September because this situation is like nothing we've seen before.
I believe the chart you identify as 'Wipneus area' is actually extent
There's an undeniable relationship between 2010's September ice pack shapes and the underlying bathymetry, what you are mentioning are especial regional cases and second-order effects.
I think following the melt and freeze seasons in the context of the bathymetry would be very revealing and may help us understand how the future will look. I would love to see the melt season matched with a detailed bathymetry map like the one attached.
People look at peripheral seas and the ´high arctic seas´developments and that is as good as it gets. How would you add the data? Divide area per depth?Distance to landmass is probably a result of currents over time?
Quote from: Glen Koehler on July 29, 2019, 03:06:47 PM IMHO the one thing 2019 was missing to get real low I have some issues with that wording because:Why WAS missing, the melting season and it's outcome are not yet overWhy "to get real low" after all we ARE in fact LOWEST on record for quite some time nowand in total this year.I suggest to wait another 30-40 days for such kind of verdict. Once 2019 should be behind 2012 so much that only a miracle could do a turnaround, your reasoning could become valid IMHO
July 24-28.
Quote from: Sterks on July 29, 2019, 05:25:38 PMThere's an undeniable relationship between 2010's September ice pack shapes and the underlying bathymetry, what you are mentioning are especial regional cases and second-order effects. apologies
Shocking. Huge areas on the Pacific and Asian sides look increasingly vulnerable.
Am I the only one shocked by seeing less than 90% concentration in the heart of what used to be the MYI overwintering zone just north of Greenland and Ellesmere Island? Is that as weird as I think it is?
I don't think 2019 will beat 2012 in extent and area. But it will be close.The CAA is still going pretty solid and the Atlantic side is definitely not going to be crushed like 2012.
Another region that bears watching over the next few days is the area north of Greenland, just east of to where the last remaining expanses of thick multiyear sea ice are clinging to the islands clustered at the north end of the Canadian Arctic. As noted in the Arctic Sea Ice Forum, very mild air, warming even more as it descends, will be flowing off the north coast of Greenland in the next several days. Satellite imagery over the last few days shows a crack developing where a large zone of Arctic sea ice is attached to the north coast of Greenland.
There's a relationship with bathymetry during the process to minimum, but it's not necessarily that closely related to deep water.edit: my argument is very weak. I just didn't like Rich using my stuff to push himself forward. I'll have to work on that.
