Today, the center of 2013’s Persistent Arctic Cyclone of May and June transitioned to Baffin Bay and the Canadian Archipelago. Forecast models show the storm lingering there over the next 24 hours, then briefly redeveloping in the Central Arctic on Thursday and Friday before finally transitioning on out of Baffin Bay by Sunday. If this forecast holds true, a storm that developed in late May and persisted to fracture and melt a broad swath of sea ice from Svalbard to the East Siberian Sea, will finally be done.
(PAC 2013 over the Canadian Archipelago and North Baffin Bay on June 18. Image source: DMI)
The storm’s legacy, should it transition away from the Central Arctic as forecast, will likely leave impacts throughout this summer and beyond. The large area of fragmented and thinned ice left in the wake of PAC 2013 is more vulnerable to melt as June, July, and August progress. And a controversy among scientists, researchers, and Arctic and climate enthusiasts over if and how much PAC impacted the 2013 melt season is also likely to ensue, perhaps lasting for years after this melt season.
Already, a number of excellent blog posts on the subject of PAC 2013 have been published. Two that are certainly worth reading appear over at the Arctic Ice Blog and on FishOutofWater’s Daily Kos page. At the center of this controversy will likely be the issue of whether or not PAC 2013 enhanced or impeded melt. An issue arising from the new possibility that human warming enables summer storms to melt and thin Arctic sea ice.
This new possibility emerged in the wake of the Great Arctic Cyclone of 2012, which is shown to have melted about 250,000 square kilometers of sea ice, contributing to, but not causing, the record melt seen in that year. 2013’s PAC is likely to prove even more controversial due to the fact that its primary action was to thin and fragment thicker ice during June, rather than blow large holes in already weakened ice during August.
Regardless, the discussion will probably be far-flung. Just one more aspect of our evolving understanding of a rapidly changing Arctic.
Not Quite Done Yet
PAC 2013 is not done quite yet, though. So here’s a basic assessment of its, likely, last days.
As noted above, PAC 2013 is expected to transition to Baffin Bay, then re-develop over the Central Arctic, before retracing its steps through the Canadian Archipelago and, finally, out of the Arctic. It will be very interesting to see what happens to the remaining Baffin Bay sea ice, which has been substantially thinned during the June melt and may now see impacts from this storm.
Here is the ECMWF model run for June 20th showing a 985 mb PAC about the eject itself from the Arctic:
(Image source: ECMWF)
It is also worth noting a very strong ‘warm side’ to this PAC persisting over Alaska and the Beaufort Sea. This particular region of warm weather has spawned some very hot temperatures over Alaska and resulted in a broad swath of melt lakes forming over the Beaufort, Chukchi, and East Siberian Seas. This particular warm air pulse has lasted for at least a week and may have consequences for mid-to-late June melt (I’ll be exploring this Alaskan Heatwave more in another blog).
PAC’s transitions over the thickest ice appear to be having impacts, which you can see in the US Navy’s CICE model runs below:
(Image source: US Navy)
Note the substantial reductions and fragmentation in the large pack of thick ice just north of Greenland and the Canadian Archipelago even as the already fractured ice from Svalbard to the East Siberian Sea continues to thin and break.
It is also worth noting that the CICE/HYCOM model shows substantial impacts you would expect from a PAC continuing on until June 25. Whether this is indicative of a disagreement between US Navy and ECMWF models on the length of PAC duration or just a projection of after-effect is unclear.
To this final point, one caution. Though models now show the absence of PAC 2013 from June 22 on, this particular storm has shown a dogged resilience. Further, even after the ECMWF model shows PAC 2013’s exit, a number of smaller storms are shown to enter and leave the Central Arctic. So it’s not, as yet, a decisive end to stormy conditions there.