Click on image to enlarge.

Coinciding with the Siberian air freezing Niagara Falls and extending frigid temperatures as far south as Carolina, Arctic ice extent got quite variable in the North Pacific, especially in Okhotsk on the left.  The image above shows how ice in that basin shuffled forward, backward and forward again.

Mid-December Okhotsk Sea on the left began growing ice steadily to reach half of 2017 March max, then inexplicably lost over 300k km2 of ice in just four days. In the last nine days it more than gained back the loss.  Meanwhile, Chukchi (upper right) was frozen completely, then retreated, and now closed again.  Bering Sea on the right has been advancing steadily but more slowly than average.

Ice extents for January appear in the graph below; 2018 is shown to date, other years for the full month.  11 year average is 2007 to 2017 inclusive.

Note that 2007 catches and exceeds the 11 year average ending the month tied.  2017 and 2018 are adding ice at nearly average rate but started with deficits to average. SII 2018 has fallen further behind.

Below is the analysis of regions on day 008.  Average is for 2007 to 2017 inclusive.

Note that 2018 deficit to average comes mostly from Bering and Barents Seas. The recovering ice in Okhotsk is now above average but still below last year, when Okhotsk accounts for the difference.

Background:  Updated Winter Forecast by Dr. Judah Cohen, January 8, 2018

Dr. Judah Cohen of AER published his current Arctic Oscillation and Polar Vortex Analysis and Forecast on January 8, 2018. His comments are always enlightening, and particularly so this time. Excerpts in italics with my bolds.

A minor but regionally very impactful stratospheric PV disruption promoted persistent cross polar flow that emptied Siberia of its cold air and carried it on a direct route to Southeastern Canada and the Northeastern US over the past two weeks. The historic cold of the past two weeks has placed the Eastern US in a position to finish with a cold winter but in no way, has guaranteed the outcome. I am of the opinion that for the winter in the Eastern US to finish with an overall cold solution then at least one other stratospheric PV is necessary but still may not be sufficient. Given the magnitude of the most recent cold air outbreak either a minor or major PV disruption could be enough to ensure a cold winter in aggregate over the three months from December through February.

I would argue that whether the winter will finish in the warm or cold column is science vs. art (at least my own artistic rendition). The science says that the second half of winter will be warm across the Eastern US including the remainder of January and all of February. All dynamical forecasts including most climate forecast system (CFS) forecasts, the national multi-model ensemble (NMME) and the European models all forecast warm see Figure i).

My own instinct tells me the winter will end in the cold column. Of course, the AER winter forecast predicts a cold winter based on Siberian snow cover, Arctic sea ice and tropospheric precursors. But my instinct or gut feeling is based on different metrics – the period of cold, northeastern snowfall and temperature records.

There have been some famously cold Decembers followed by a relatively mild remainder of winter. The two that most readily come to my mind are winters 1983/84 and 1989/90. One more recent but not as dramatic was winter 2005/06. And if my recollection is correct, those cold Decembers transitioned from cold to mild around the holiday season. I cannot recall a mild winter when the cold from December extended into January.

The second is significant snowfall in the I95 corridor. Again, I can’t recall a snowstorm this early in the season of the magnitude of this week’s blizzard occurring during mild winters. I certainly can’t recall any in 1983/84, 1989/90 or 2005/06, though in that last winter there was significant snowfall in February.

Finally, are record temperatures mostly in January. It seems to me that record cold or warm temperatures are an early indication of the overall winter anomaly. Record warm temperatures occur in an overall warm winters and record cold temperatures in an overall cold winter and less so vice versa. I do believe fairly strongly that Nature likes to foreshadow and those are some of the foreshadowing markers that I follow.

Interestingly below normal or convergence of vertical Wave Activity Flux (WAFz) is predicted in the troposphere for next week. This actually favors increased high latitude blocking and may explain the return of strong Alaska ridging with downstream eastern North America troughing and cold weather. But rather than a committed turn to the cold path this appears to be more of a head fake and more mild weather is predicted for the third week of January. Therefore, the return to mild weather in the Eastern US makes me believe we still remain situated at the fork in the road without a full commitment to either the mild or warm path. Though if the GFS forecast of cold reloading in Canada is correct, I think that it is almost inevitable for that cold to slide down into the lower 48 with time.

Put in other words the fork can be represented by the divergence in the polar cap geopotential heights (PCHs) between the troposphere and the stratosphere. PCHs are overall warm/positive in the troposphere while PCHs are overall cold/negative in the stratosphere. In probably overly simplistic terms I am waiting for convergence of either warm or cold PCHs throughout the troposphere and the stratosphere before claiming winter has fully committed to a cold (universal warm PCHs) or mild (universal cold PCHs) winter.

Whichever fork the ice takes, the Polar Bears had a very happy New Years Day.

Click on image to enlarge.

With 2017 ice extent estimates complete we can look at the year in perspective.  Above is a graph showing the annual average extents since 2007, comparing MASIE and SII (v3.0).  Obviously, the trend in MASIE could not be flatter, while SII shows a decline.  The first five years the two indices were nearly the same, and since then SII shows less ice, about 260k km2 each year.  Note also how small is the variance year over year: Standard deviation is +/- 260k km2, or about 2.5% of the average annual extent.  This holds for both indices.  Note also a pattern of three higher years followed by two lower years.

A previous post Sea Ice Index Updates to v.3.0 reported on the newest SII version, and we can see how it compares with MASIE over this last year.

Click on image to enlarge.

The first four months show more diversity, both in the 10 year averages and in 2017 results. From May on MASIE 2017 tracks closely to its average, while SII shows 2017 below its average every month. For those who want to see the numbers a table is provided below.

Some are proclaiming dire warnings about melting ice and imagining various dangerous impacts. Some fluctuations do appear but not very large and somewhat cyclical. Since 2007 it resembles a plateau more than anything else.

Background on MASIE Data Sources

MASIE reports are generated by National Ice Center from the Interactive Multisensor Snow and Ice Mapping System (IMS). From the documentation, the multiple sources feeding IMS are:

Platform(s) AQUA, DMSP, DMSP 5D-3/F17, GOES-10, GOES-11, GOES-13, GOES-9, METEOSAT, MSG, MTSAT-1R, MTSAT-2, NOAA-14, NOAA-15, NOAA-16, NOAA-17, NOAA-18, NOAA-N, RADARSAT-2, SUOMI-NPP, TERRA

Sensor(s): AMSU-A, ATMS, AVHRR, GOES I-M IMAGER, MODIS, MTSAT 1R Imager, MTSAT 2 Imager, MVIRI, SAR, SEVIRI, SSM/I, SSMIS, VIIRS

Summary: IMS Daily Northern Hemisphere Snow and Ice Analysis

The National Oceanic and Atmospheric Administration / National Environmental Satellite, Data, and Information Service (NOAA/NESDIS) has an extensive history of monitoring snow and ice coverage.Accurate monitoring of global snow/ice cover is a key component in the study of climate and global change as well as daily weather forecasting.

The Polar and Geostationary Operational Environmental Satellite programs (POES/GOES) operated by NESDIS provide invaluable visible and infrared spectral data in support of these efforts. Clear-sky imagery from both the POES and the GOES sensors show snow/ice boundaries very well; however, the visible and infrared techniques may suffer from persistent cloud cover near the snowline, making observations difficult (Ramsay, 1995). The microwave products (DMSP and AMSR-E) are unobstructed by clouds and thus can be used as another observational platform in most regions. Synthetic Aperture Radar (SAR) imagery also provides all-weather, near daily capacities to discriminate sea and lake ice. With several other derived snow/ice products of varying accuracy, such as those from NCEP and the NWS NOHRSC, it is highly desirable for analysts to be able to interactively compare and contrast the products so that a more accurate composite map can be produced.

The Satellite Analysis Branch (SAB) of NESDIS first began generating Northern Hemisphere Weekly Snow and Ice Cover analysis charts derived from the visible satellite imagery in November, 1966. The spatial and temporal resolutions of the analysis (190 km and 7 days, respectively) remained unchanged for the product’s 33-year lifespan.

As a result of increasing customer needs and expectations, it was decided that an efficient, interactive workstation application should be constructed which would enable SAB to produce snow/ice analyses at a higher resolution and on a daily basis (~25 km / 1024 x 1024 grid and once per day) using a consolidated array of new as well as existing satellite and surface imagery products. The Daily Northern Hemisphere Snow and Ice Cover chart has been produced since February, 1997 by SAB meteorologists on the IMS.

Another large resolution improvement began in early 2004, when improved technology allowed the SAB to begin creation of a daily ~4 km (6144×6144) grid. At this time, both the ~4 km and ~24 km products are available from NSIDC with a slight delay. Near real-time gridded data is available in ASCII format by request.

In March 2008, the product was migrated from SAB to the National Ice Center (NIC) of NESDIS. The production system and methodology was preserved during the migration. Improved access to DMSP, SAR, and modeled data sources is expected as a short-term from the migration, with longer term plans of twice daily production, GRIB2 output format, a Southern Hemisphere analysis, and an expanded suite of integrated snow and ice variable on horizon.

http://www.natice.noaa.gov/ims/ims_1.html

Footnote

Some people unhappy with the higher amounts of ice extent shown by MASIE continue to claim that Sea Ice Index is the only dataset that can be used. This is false in fact and in logic. Why should anyone accept that the highest quality picture of ice day to day has no shelf life, that one year’s charts can not be compared with another year? Researchers do this, including Walt Meier in charge of Sea Ice Index. That said, I understand his interest in directing people to use his product rather than one he does not control. As I have said before:

MASIE is rigorous, reliable, serves as calibration for satellite products, and continues the long and honorable tradition of naval ice charting using modern technologies. More on this at my post Support MASIE Arctic Ice Dataset

Arctic ice extent grows slowly this time of year since many regions are already covered completely.  In recent days 2017 reached 84% of the maximum last March, but dropped below the 10 year average.  As we can see, most of the action was a dramatic seesaw in Okhotsk Sea, a Siberian basin in the North Pacific.

Mid-December Okhotsk Sea on the left began growing ice steadily to reach half of 2017 March max, then inexplicably lost over 300k km2 of ice in just four days.  Meanwhile, Chukchi (upper right) froze completely, then retreated somewhat.  Bering Sea on the right has been advancing steadily but more slowly than average.

The overall effect in December is shown in the graph below:
Note that 2007 matches the 10 year average, while 2012 is well above.  Lagging behind are 2016, 2017 and SII 2017.  This year’s deficit to average appears in the last 11 days, mostly due to Bering and the Okhotsk year end surprise.
Most of the month combined Bering and Okhotsk (B&O) extents were average, until the inexplicable drop starting day 361. Except for those two seas, the month was unremarkable.
At year end, 2017 NH ice, excluding B&O, is down about 200k km2, or 2% of average.  Below is the analysis of regions on day 365.

Most of 2017 deficit is in Bering and Barents, less so in Okhotsk with yesterday’s recovery.  Perhaps the Polar Vortex sent frigid air into the US and Canada and replaced it with warmer southern air, and ice receded as a result.  I have reported on Arctic incursions in a post Arctic Inversions and Intrusions but the speed of the effect on ice (if that is the phenomenon) is still surprising.  We shall see if it persists or not.

Background:  Winter Forecast by Dr. Judah Cohen, Dec. 25

On Christmas Day Dr. Judah Cohen published his updated Arctic Oscillation and Polar Vortex Analysis and Forecast  Excerpts below

As I have been discussing the past two blog posts I continue to believe that this is the most critical period of the winter and will ultimately determine the character of the winter. In my opinion, we have approached a fork in the road and the atmosphere can take two possible paths one is a path where the rest of the winter is relatively mild across the mid-latitudes of the NH and the second is a colder path or solution. The tropospheric polar vortex has been relatively weak for much of the month of December as illustrated by the relatively warm polar cap geopotential heights (PCHs) for the first half of December that then boomeranged off the mid-stratosphere and after a short respite with colder tropospheric PCHs, warmer PCHs in the troposphere are predicted through the end of the month and into early January.

Based on the easterly phase of the Quasi-Biennial Oscillation (QBO) I have been favoring a significant PV disruption most likely in January for much of the fall.  A significant stratospheric PV disruption would then be followed by an extended period of severe winter weather across the mid-latitudes of the NH.  However, I have to admit as of yet there are no signs of this scenario.  There is still time but not much.  However, there is another scenario that could still yield a relatively cold winter and that is one analogous to what happened in the winter of 2013/14 where no significant disruptions of the stratospheric occurred but rather repeated minor disruptions that yielded a cold winter for central and eastern North America. Though at first, I acknowledged this possibility I was hesitant to favor this scenario.  However, the longer the delay in a major disruption of the stratospheric PV the more I favor this scenario.

The Arctic Oscillation (AO) is currently slightly positive and is predicted to trend slowly negative through the end of the week towards neutral. The forecast is for the AO to remain close to neutral next week, likely a sign of uncertainty.

Figure 7. Forecasted snowfall anomalies (mm/day; shading) from 31 December 2017 – 4 January 2018. The forecasts are from the 00Z 18 December 2017 GFS ensemble. Note the new projection to provide finer resolution.

The current positive AO is reflective of mixed pressure/geopotential height anomalies across the Arctic and mostly positive pressure/geopotential height anomalies across the mid-latitudes. The North Atlantic Oscillation (NAO) is also currently slightly positive with weak pressure/geopotential height anomalies across Greenland and Iceland and positive pressure/geopotential height anomalies across the mid-latitudes of the North Atlantic.

A return to Ural ridging/blocking at the turn of the calendar year favors active energy transfer from the troposphere to the stratosphere. Another pulse is predicted to commence this week and peak the first few days of January. The pulse itself is likely related to relaxation of the pattern and mild temperatures across North America. However, the predicted resultant perturbation to the stratospheric polar vortex (PV) especially the building of heights over northwestern North America in my opinion could once again favor the return of cold temperatures across eastern North America later in January.

Figure 9. Forecasted snowfall anomalies (mm/day; shading) from 5 – 9 January 2018. The forecasts are from the 00Z 25 December 2017 GFS ensemble. Troughing and/or cold temperatures will support the potential of additional snowfall across Eastern Europe, Siberia, West and East Asia, Alaska, Canada and the Northwestern US. Despite below normal temperatures, temperatures warm sufficiently to support snowmelt across the Eastern US (Figure 9).

Ice did not grow this past week on the North Pacific side of the Arctic basin, still I expect the negative ice anomalies in the region to shrink.  Sea ice is below normal in the Barents-Kara Seas as well and with time the greatest negative sea ice anomalies will likely reside in this region.  As I have been writing for much of the fall I do believe that the record low sea ice anomalies in the Chukchi and Bering Seas has focused ridging/blocking in this region.  Though model forecasts do not predict a return of the blocking in the foreseeable future.

Recent research has shown that regional anomalies are important and the sea ice region most highly correlated with the winter AO is the Barents-Kara Seas region where low Arctic sea ice favors a negative winter AO and a cold Eurasia.  Below normal sea ice in this region may be contributing to more active Wave Activity Flux/poleward heat transport predicted in the models that eventually could result in a negative AO.

As we have seen, the Polar Vortex did indeed return to North America, freezing Niagara Falls in the process.

Whichever fork the ice takes, the Polar Bears had a Merry Christmas