Terry asks: can low pressure systems in the Bering sea cause barotrophic flows of Pacific waters over the 50 m sill barrier into the Chukchi enough to affect winter freeze-up?
Bering Strait inflow can be quite significant at almost a cubic km per second (0.8 sverdrups, about 2/3 all the world’s rivers, according to three Bering Strait moorings over 20 years) but variability of volume and location of currents is quite high, even over the course of a single day. There is no simple scheme at present that explains or predicts inflows according to 2015-16 reviews of R Woodgate, the principal oceanographer for the Straits. One component, the warm Alaskan Coastal Current, follows the coast well into the Beaufort.
Moorings are retrieved once a year, so our best daily option for detecting another surge in heat transport this winter is probably Hycom sea surface salinity and temperature animations. Right now, strong winds blowing south out the Straits will reduce inflows, which in any event are only one contributing factor to freeze-up despite the huge difference in heat content and conductivity of water relative to atmosphere.
Note a substantial fraction of the Arctic Ocean lies within the 50 m bathymetry contour — nearly all the Chukchi and ESS but not so much the Beaufort. Thus a cubic km per second for a day fills 50 m x 20 sq km x 86.400 ksec, or a surface patch 1730 sq km in area if extending to the sea floor, so about a year’s worth at actual mean inflow to amount to the Chukchi’s 528,000 sq km (as defined in Serreze 2016). Depending on mixing and buoyancy, the heat could be localized in near-surface water affecting the ice front with increased salinity slightly lowering freezing temperatures.
NeilT asks: doesn’t natural variation about a baseline continue even in times of rapid change?
Yes and no. The weather will continue to be chaotic, indeed more so than ever (because of increased energy and water vapor in the system aka sampling from a larger phase space). However variation on a 1950-1980 baseline or a 1978-2008 satellite record has ever-decreasing relevance. There would be a nice new baseline in the works eg 2016-2048 if only climate change would slow down. However 2017, 2018, 2019 … may be so different from 2016 etc (after discounting natural variability applicable to that year) such that each will require its own baseline yet items such as mean and std deviation are observationally unobtainable over such short time frames.
So a decomposition into baseline plus weather is no longer a viable option. The underlying reason is Arctic feedbacks are overwhelmingly of the runaway kind as the system approaches the seasonally ice-free summer/fall and styrofoam-covered winter ice of the Arctic heat budget end-game.
It's unfortunate that so many stopped following this unprecedented fall refreezing season after some silly map integral record was set; one number on one day cannot capture much of anything other than a buried headline. Late February will bring a superficially similar ice cover to earlier years, covering up significant consequences of this fall. Here R Scribbler is on to something better with the ‘end of winter as we know it’.
Right now, the Arctic Ocean is experiencing a very strong cyclonic event bring warm wet air up from mid-latitude. Nasa just put up a very nice animation of a similar event in late Dec 2015 which seems to have fallen below the forum radar screens back then,
The current 15 Nov 2016 event is shown unfolding below. Watch the color overlays of wind for colors from the south that have penetrated to the north. As noted in the Nasa voice-over, warm moist air from mid-latitude is deleterious to ice formation and net radiation from open water to space. Three ‘moisture’ channels are included in the slide show though quantitative effects are murky. The Arctic Ocean was described as arid in years gone by.
Since the main ice pack is fairly solid by now, that which doesn't fracture and rotate about Kap Morris Jesup will pivot with the applied wind as a block, away from the Svalbard-FJI axis on the Atlantic side, including withdrawal from the St Anna Trough; Fram export of the very oldest, thickest ice will be high; and on the Pacific side, marginal brash ice will get pushed into the Chukchi, still warm from the Bering Sea anomaly. Thus the melt season is continuing somewhat in dodgy ice of the Barents and East Siberian Sea in mid-November even as refreezing proceeds.
At this time of year, AMRS2 open water provides an accurate one-click counterpart to algorithmic extent. We'll need to check back in a week to see how the ice surface responded to this cyclonic event. The 50 m bathymetry below scale is set to co-register with UHH AMSR2.
As a technical note, nullschool time series are best made by setting up the view, moving the date by (shift) J or K, capturing whole-window screenshots for co-registered layers that can be cropped. If the url contains ‘current’, it is unstable; if the lat,lon are chosen sensibly, the image won’t need a rotation to register with products such as ice cover; even the scale parameter can be adjusted to improve fit.
https://earth.nullschool.net/#2016/11/15/1200Z/wind/surface/level/overlay=total_precipitable_water/stereographic=-45.00,89.17,1808ftp://ftp-projects.zmaw.de/seaice/AMSR2/3.125km/Arc_20161115_res3.125.png