Arctic sea ice is disappearing at a record pace this summer. Please open this interactive website for a clear picture that is easy to follow with day-by-day comparisons to other years: https://ads.nipr.ac.jp/vishop/#/extent/&time=2019-04-01%2000:00:00 Until a week ago this year’s melting progress was keeping pace with the decline rate of the three previous record years, but not doing any worse. In the past week, as you can see, this has all changed, in the form of a sharp plunge. The normal period of greatest declines has only begun and will last another six weeks or so. I would have to bet on 2020 remaining well in the lead at that point. In the following and final month of declines 2012 proceeded to set a record that has held ever since, aided by effects due to extreme winds, and will again be hard to overtake. This year’s finish for the top spot in September should be a tight one.
The “advantage” that 2020 will have in the near future starts with the fact that the entire ocean is now being overrun by an unusual influx of high-altitude water vapor. This is happening and will continue to happen as long as there are practically no jetstream winds standing in the way. They have been disappearing as a result of changes imposed on the configuration of high-altitude air pressure readings, where the normal pressure gradients that house these winds have been substantially weakened in recent weeks. This image is illustrative:
Streams of air bearing relatively high volumes of water vapor can now easily gain access to the polar atmosphere from both the west and the east without serious interruption. They have no doubt already begun to add substantial amounts of energy to the surface below by means of their potent greenhouse effect. This extra energy is being employed to both hasten the melting of ice and add to the warming of newly exposed ocean water, with a pronounced effect on surface air temperature soon to follow. On this map you don’t see much of an air temperature anomaly at the present time since all temperatures—ice, meltwater and air—are stuck together in a heat exchange at right around the melting point, with ice in control. It will all change as the ice disappears.
Once the air over the ocean starts warming the stage would be set for regular development of a temperature feedback loop, making it difficult for jetstreams to regain full strength after the summer season has ended. The key effect of the loop is such that a little extra water vapor is always allowed to slip through when jetstreams have been softened up, and as the vapor slips through, regardless of the time of year, whatever heating it can add will contribute to even further seasonal debasement of the jetstream winds. Such water vapor intrusions next winter will of course be a far cry from the level of those now in effect, but even a little bit more than normal must have considerable leverage at that time of year, as noted in recent letters describing current events in Anarctica.
Carl