Almost continuous warm, moist air invasions of the Arctic during fall and winter of 2016 and 2017 have resulted in the lowest sea ice refreeze rates on record. As a result, the amount of ice covering sections of the Northern Hemisphere ocean is now remarkably lower than during past comparable periods. In other words, we’ve never seen a winter in which Northern Hemisphere sea ice was so weak and reduced.
One key measure, sea ice volume, has shown particular losses when compared to past years. And even taking into account a long term trend of ice losses for the northern polar region that has been ongoing since the 20th Century, the 2016-2017 losses stand out like a flashing red indicator light. A trend directly related to the human-forced warming of our world through fossil fuel burning and related greenhouse gas emissions.
(Significant sea ice losses during the winter of 2016-2017 show up clearly in the above PIOMAS graph. PIOMAS is a model measure of sea ice volume. And as you can well see when looking at the red line at the left hand side of the graph, the departure from past years is currently quite large. Image source: PIOMAS.)
In the above PIOMAS graph we find that January sea ice volume averaged around 14,000 cubic kilometers. This reading is roughly comparable to the early July average for the period of 1979 through 2016 — a time when the Arctic saw continuous declines in sea ice. The present reading is also about 1,500 cubic kilometers below the previous record low for the month of January set in 2013. And anyone looking at the above graph can well see that the departure is significantly below the trend line (about 8,000 cubic kilometers below the falling 38 year average for this time of year).
It’s worth reiterating that these are the lowest sea ice volumes ever seen for this time of year in the Arctic. A new record that comes after consistent new record lows occurring throughout the past 38 year period.
Presently, approximate 5 C above average temperatures are dominating the region above the 66 North Latitude. Over the coming days, a pair of warm air invasions of the North Pole region near 90 N are expected to push temperatures to more than 30 degrees Celsius above average and to near the melting point on two separate occasions. This pair of, not at all normal, events will likely produce additional sea ice losses in a polar region that is already seeing very unusual low sea ice concentrations, volumes and extents.
(Warm storm invasions of the northern polar region that inject high heat content, ice-melting moisture and far above average temperatures into the High Arctic have been a frequent occurrence over recent months. By February 10, GFS models predict that another such storm will push temperatures to more than 30 degrees Celsius above average for the North Pole and surrounding regions. This will produce yet one more powerful blow to sea ice attempting to rebuild in the region. Image source: Earth Nullschool.)
After these events roar through, the Jet Stream is predicted to flatten somewhat — allowing cooler air to re-establish over the Central Arctic as warmer air invades the mid-latitudes. As a result, air temperature anomalies in the 66 N and above region are expected to fall back to a range of 1 to 2 C above average in the 7 to 14 day timeframe. Such a return to closer to normal conditions may allow for more short-term bounce-back toward previous record low ranges in the volume measure. But a much longer period of closer to average conditions would be required for a full recovery.
Overall, refreeze season tends to last until April. So some time does remain for a bit of recovery. And we have seen extent measures trend closer to past record lows over recent days. However, considering the massive losses experienced during fall-winter of 2016-2017, two months is unlikely enough time to produce a significant recovery even if cooling to more reasonable above average temperatures were to occur and remain in place for an extended period.