As of late October 2016, large areas of open water remain in the Beaufort, Chukchi, Bering Straits, and East Siberian Sea. The peripheral surface waters are far too warm for ice to stably form — in places some 4º C above the freezing point (-1.9º at surface salinity) — except in the eastern Beaufort and Laptev seas.
The Beaufort, Chukchi and Barents seas are seasonally ice-free now, with all that that implies. We need not wait until 2050, it’s here now. The Beaufort had significant areas of open water by the 1st of May this year and still has not frozen over six months later.
This development in the Chukchi is primarily attributable to to long fetches of open water allowing strong winds to turbulently mix surface with lower warmer water, to large and increasing inputs of warm Pacific Water crossing the 50m x 85km sill at the Bering Strait, teleconnections of an El Nino year and Pacific blob, persistent Arctic Ocean cloud cover reflecting back radiated heat, for which the stage has been set by long term trends in sea ice loss due to global warming and its Arctic amplification.
The 55-day time series below shows sea surface temperature anomalies (SSTA) and sea surface temperature (SST) at 70º N, 170º W (green circle) and the sea ice edge response to conditions (AMSR2 zero ice concentration envelope, yellow line). Solar input has ceased; colder air temperatures are ineffectual at cooling large volumes of mixed water — the meagre heat capacity and low conductivity of air are no match for wind-mixed waters or the recent and continuing surge through the Bering Strait suggested by surface salinity data. However air temperatures themselves have been most anomalously warm, see
https://twitter.com/ZLabe/status/790579202181390336The mean October anomaly at the indicated site is 2.3º C above the average sea surface temperature of 4.3º. It’s feasible to obtain these statistics regionally (over each daily expanse of open water) using the AMSR2 mask to restrict a contoured version of the nullschool display, but probably better to retrieve the raw data product RTG-SST/NCEP/NWS or its daily contour map.
Sea ice-dependent marine mammals such as walruses reach feeding grounds by resting on floes carried by wind and current; an embedded sub-animation shows a walrus shaking its head as it fades to near-oblivion on the final frame. On October 24th, the nearest ice to Barrow AK was 448 km to the north. The first few kilometers of that gray/pancake/underwater frazil ice would not support the weight of a gerbil.
Indeed the Arctic Ocean has not frozen north of Svalbard either, which is 730 km farther north than Barrow and just 1050 km from the north pole. The issues here are different for the Barents though, involving the Atlantic Water currents and a close-in continental shelf.
The Arctic Ocean does not need a ‘black swan’ event any more to fall catastrophically below its trend line, a gray swan event will do. That’s weather conditions well within normal variation but ill-timed: sunny weather during early melt season, strong cyclones in August, persistent warm and humid air brought in by lower latitude hurricanes, steady pressure dipoles whose winds expors ice out the Fram, and so on. Here the black swan of September morphs to white by the end of October to represent the Chukchi and Bering Straits are not freezing up as in the past (3rd and 4th animations).
Some very recent scientific articles describe the currents and heat inputs across the Bering Strait and analyse the satellite record in this area. Note though that an article published in October 2016 will have a data cutoff of 2014, but the 37 abstracts at this December’s AGU2016 mentioning the Chukchi or Beaufort bring these up to date..
Emerging trends in the sea state of the Beaufort and Chukchi seas
J Thomson et al
http://dx.doi.org/10.1016/j.ocemod.2016.02.009http://archimer.ifremer.fr/doc/00345/45590/45202.pdf free full text
The sea state of the Beaufort and Chukchi seas is controlled by the wind forcing and the amount of ice-free water available to generate surface waves. Clear trends in the annual duration of the open water season and in the extent of the seasonal sea ice minimum suggest that the sea state [ie waves] should be increasing, independent of changes in the wind forcing…. The increase in wave energy may affect both the coastal zones and the remaining summer ice pack, as well as delay the autumn ice-edge advance [to the extent waves hit the edge].
A Synthesis of Year-Round Interdisciplinary Mooring Measurements in the Bering Strait (1990–2014)
RA Woodgate et al
Oceanography | September 2015
http://tos.org/oceanography/assets/docs/28-3_woodgate.pdf free full text
Although the volume transport of the Alaskan Coastal Current (ACC) of ~0.1 Sv is small compared to the full Bering Strait throughflow of ~0.8 Sv [which in turn is a quarter of Atlantic Waters entering at the Barents at 3.2 Sv], the ACC is 5ºC warmer and 7 psu fresher than the main waters of the strait, it carries a third of the heat and onequarter of the freshwater flux of the Bering Strait.
Perhaps most dramatic interannual variability is the increase in Bering Strait volume flux from 2001 to 2013 from ~0.7 Sv to ~1.1 Sv, almost a 50% increase in the flow. Since to first order whatever enters the Bering Strait must exit the Chukchi Sea into the Arctic Ocean, this increases ventilation of the Arctic halocline, decreases residence time in the Chukchi by several months, and increases oceanic heat flux.
Since Pacific waters exit the Arctic via the Fram Strait and the CAA at near-freezing temperatures, this allows us to quantify the heat lost from the Pacific waters somewhere in the Chukchi/Arctic system. Including corrections for the ACC and stratification, calendar-mean Bering Strait heat fluxes are 3 6 x 1020 J/ yr 1 (or 10 -20 TW, comparable to shortwave solar input to the Chukchi Sea.
This quantity of heat is sufficient to melt 1-2 million square km of 1 m thick ice. Bering Strait heat flux may act as a trigger to create open water upon which the ice albedo feedback can act, and also provides a year-round subsurface source of heat potentially thinning Arctic sea ice, since Pacific summer waters are found in half the Arctic Ocean.
Variability, trends, and predictability of seasonal sea ice retreat and advance in the Chukchi Sea
MC Serreze, AD Crawford, JC Stroeve, AP Barrett, RA Woodgate
J. Geophys. Res. Oceans,121, doi:10.1002/2016JC011977 (2016) blocked access, figures available
As assessed over the period 1979–2014, the date that sea ice retreats to the shelf break (150 m contour) of the Chukchi Sea has a linear trend of 20.7 days per year. The date of seasonal ice advance back tothe shelf break has a steeper trend of about 11.5 days per year, together yielding an increase in the open water period of 80 days.
Based on detrended time series, we ask how inter-annual variability in advance and retreat dates relate to various forcing parameters including radiation fluxes, temperature and wind, and the oceanic heat inflow through the Bering Strait (from in situ moorings). Of all variables considered, the retreat date is most strongly correlated with the April through June Bering Strait heat inflow. Predictability will likely always be limited by the chaotic nature of atmospheric circulation patterns.
Enhanced heat fluxes from the ocean back to the atmosphere in autumn and winter is a major driver of Arctic amplification — the outsized rise in Arctic surface air temperatures relative to the rest of the planet. Whether the effect of ice loss on Arctic amplification extends through a deep enough layer of the troposphere to alter jet stream patterns with impacts on middle-latitude weather is a vibrant area of debate.
GC24A-01: Sea State and Boundary Layer Physics in the Emerging Arctic Ocean
Tuesday, 13 December 2016 Moscone West - 3005
The sea state of the Arctic Ocean is changing. With an increasing retreat of sea ice in the summer months, storms are now more likely to occur over open water, and the result is an increasing trend in both the heights and periods of surface waves in the Chukchi and Beaufort Seas. The elevated sea state affects, in turn, the refreezing process in the autumn. In 2015, a field campaign collected a comprehensive suite of air-ice-ocean measurements during the autumn freeze-up in the Beaufort Sea, and these measurements are used to investigate the surface wave effects and coupled dynamics.
The most prominent process is the formation of pancake ice, which occurs when surface wave motions disturb newly forming frazil ice. Analysis of a wave event from open water through different stages of a gradually maturing pancake ice cover shows high sensitivity of the surface waves to the types of ice cover. Other cases suggest that waves impact the near-surface heat flux convergence, impacting the ice formation. Hence, there is a two-way interaction between ice and waves. Wave attenuation is captured with adjustment of a viscoelastic parameterization in a wave hindcast model. The results suggest that a fully coupled air-ice-wave model will be necessary to describe the evolution of sea state and ice cover during the Arctic freeze-up.
C31D-02: Regional Upper Ocean Variability and Ocean Heat Losses during the 2015 Autumn Ice-Edge Advance in the Chukchi and Beaufort Seas as Observed during the Sea State Field Campaign
Wednesday, 14 December 2016 Moscone West
Some of the fastest Arctic sea ice changes are happening in the Chukchi and Beaufort Seas as indicated by a much earlier (by ~49 days over the last 36 years) ice-edge retreat in spring, followed by a much later (by ~43 days) ice-edge advance in autumn (based on 1979-2014 satellite observations). The lengthening of the summer open water season and increasing fetch also mean greater upper ocean heat content and a longer, possibly stronger period of wind/wave forcing on the upper ocean and advancing sea ice cover.
To understand how surface waves and winds affect air-sea-ice interactions and consequently the timing of the autumn ice-edge advance in the emerging Arctic, a Sea State field campaign was conducted aboard NSF’s R/V Sikuliaq from 4 Oct to 5 Nov 2015. During the campaign we obtained contemporaneous in situ observations of the atmospheric boundary layer, ice cover, wave state and upper ocean along a cruise track in and out of the advancing ice cover in the Chukchi and Beaufort Seas. Vessel-underway (uCTD) profiler was used to collect over 4200 upper ocean profiles during both quiescent and stormy conditions in and outside the ice cover.
Using the uCTD data we describe the spatial variability in upper ocean structure and heat content within the context of its recent past regarding summer open water duration and wind/wave forcing, as well as regional variability in water mass characteristics. We then describe the contemporaneous air-sea-ice observations, including air-ocean energy fluxes and changes in upper ocean heat content during brief periods of ice-edge advance, loitering and retreat to explain the overall space/time evolution of the ice-edge advance in the Chukchi and Beaufort Seas during autumn 2015.