It’s a pretty well established theory. If snow over the Northern Hemisphere land and sea ice masses substantially melts during May and June, it can tend to set up a general weather pattern that is conducive to large-scale reductions of the Arctic sea ice come July, August and September.
(Arctic sea ice in very ragged condition by July 19, 2015. A situation born of a continuous Greenland and Central Arctic high pressure ridge setting up warm air build-ups and a sea ice-flushing dipole weather pattern. Image source: LANCE-MODIS.)
Arctic High Pressure, Heat, Collapsing the Sea Ice
And, during June, we saw just this kind of trend emerge. Arctic heatwaves over both the Continental land masses and the Arctic sea ice resulted in a rapid melting of snow cover. Heatwaves fed by massive bulges in the Northern Hemisphere Jet Stream, particularly along the now-famous Ridiculously Resilient Ridge over what is today an amazing (horrific) hot zone of Northeastern Pacific surface waters. El Nino and Positive PDO played their role too, kicking up the hot zones and the ridge to ever greater intensity. An atmospheric and ocean synergy in a 1 C hotter than 1880s context that kept hurling more and more heat into the Arctic environs. Melting more snow and setting the stage for a potential sea ice massacre to come.
By early July there were indications that just such an event may be on the way. A ‘heat dome’ type high pressure system had become well established over the Greenland side of the High Arctic. And for the past three weeks now, this high has remained entrenched. A persistent weather pattern that has allowed more sunlight to hit the sea ice during periods of peak insolation, a pattern that compacts sea ice in the Central Arctic, a pattern that draws storms into the Siberian side of the Arctic to chew away at the ice edge, and a pattern, that overall, drives the ice inexorably toward its Atlantic Ocean flush valve in the Fram Strait.
(Hot to record hot conditions have remained in place over the Arctic Ocean throughout July. Image source: NSIDC)
All this extra heat, transport, compaction and storms chewing away at the sea ice edge has finally started to take a very serious toll. As of today, sea ice extent measures had dropped from 7th to 10th lowest on record to 6th to 7th lowest. Area has remained at 4th to 5th lowest on record for the date. Meanwhile volume in the DMI measure has dropped to 2nd lowest on record.
Most charts now are starting to show a steep ‘cliff’ type rate of decline indicative of rapid sea ice collapse. This is particularly true in NSIDC’s Charctic and Cryosphere Today’s sea ice graphs which now show both extent and area lines plunging at rates that will rapidly cross new thresholds if they continue over the coming days.
Sea Ice Concentration in a Rough State
But perhaps most disturbing of all are the indicators that are now showing up in nearly all of the visual concentration monitors. Uni Bremen sea ice concentration continues to look like a massacre on the Pacific side. NSIDC doesn’t appear to be much better. But Cryosphere Today takes the cake for an overall display of sea ice weakness that, on the 19th (updated as the CT measure used earlier ended up being a bit off), looked nearly as bad as on the same day during the record melt year of 2012:
(Comparison of July 19, 2015 and July 19, 2012 shows 2015 looking nearly as bad as 2012 in the concentration measure. Image source: Cryosphere Today.)
Comparing the left frame image with the MODIS satellite shot at the top of this post, we find confirmation of an overall, very weak sea ice state. Concentration throughout the Arctic appears low. This is especially true on the Beaufort, Chukchi and East Siberian Sea side (see MODIS shot at bottom of post). But extensive weakness and low concentration appears to pervade the entire ice mass. Zooming in on the sea ice surface, we find that some of this low concentration is possible to confirm. The entire Arctic is now full of broken floes, polynya and melt ponds.
Though it is also possible that this extensive melt ponding (also a feature that weakens sea ice) may have kicked the Crysosphere Today concentration sensor a bit into the extreme scale (corrected during the past 24 hours), the 2012-to-2015 comparison above is still apples to apples. And what’s a bit disturbing about this comparison is the fact that much of the concentration in red (55 to 70 percent) in the 2012 measure completely melted out at the ocean surface by mid September of that year. More notably, perhaps, is the fact that the Cryosphere Today concentration measure is, at least in part, confirmed by the US Navy ARCc Concentration model which has now begun to pick up some of the earlier predicted rapid melt in the observational ensemble:
(Sea ice massacre starting to show up in the US Navy ARCc model daily observations [top frame] and continues to be predicted in the 30 day history and 7 day forecast [bottom frame]. Image source: US Navy.)
Above, we see very low sea ice concentration practically anywhere outside the 80 degree North Latitude line. Most notably, concentration is very thin and rapidly weakening in the Beaufort, Chukchi, East Siberian, and Laptev Seas. And the seven day forecast shows very rapid melt throughout all these regions with the low concentration bulge beginning to invade north of the 80 degree line on the Laptev and ESS side in particularly troubling fashion.
Forecast — Continued Rapid Melt, Some Records May be Threatened
So the question, going forward, is — what next? And it appears that the sea ice is being prepped for continued rapid to accelerating melt over at least the next 7-10 days. Seven day forecasts show the ridge remaining on the Greenland side of the Arctic throughout the period. A position that will continue the current melt, transport and ice weakening regime. Longer range, ten day, ECMWF forecasts find the high shifting more toward a strong ‘heat dome’ located in the Central Arctic with a somewhat weaker high remaining over Greenland — a minor variation of the current ice-weakening state that may slow down ice export but leave compaction, melt ponding, heat build-up, and ice edge weakening due to storms in tact.
(Sea ice throughout the Beaufort, Chukchi, ESS and Laptev is very weak. Can it survive another 10 days of the Greenland/Central Arctic heat dome? Image source: LANCE-MODIS.)
Due to this weather forecast and due to some observations beginning to come in line with ARCc model runs, we cannot rule out a very rapid melt and recession of sea ice along a broad arc running all the way from the Canadian side to East-Central Siberia. The sea ice is visibly very weak there. Perhaps the weakest we’ve ever seen it for this time of year. Ice that will continue to be pulled poleward by the highs that are forecast to remain in place. Ice that will run into weakened, melt pond invaded ice — a paltry respite for its retreat. And ice that will continue to be harried by edge storms and an influx of much hotter than normal air and water from the Pacific Ocean side. It’s a rapid melt risk that calls into effect the potential that some old sea ice area, extent, and volume records may be challenged or broken — probably not 2012’s all time low marks, but more possibly 2011 or 2007.
It’s, overall, a very tenuous situation for sea ice, one that is continuing to be fed by a growing El Nino and still firmly entrenched RRR to the south. So the evolution of sea ice melt over the next few weeks will likely be a critical game-maker for the state of Arctic Sea ice melt and the overall story of Arctic Sea Ice decline in this sad age of human-forced climate change.
UPDATED JULY 21, 2015
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