I'm curious what mechanism bbr2314 proposes for mid-latitude snow on the land to affect arctic sea ice levels.
The Cryosphere is dependent on albedo not latitude. The situation today exists only because the Arctic sea ice exists.
An equable climate is dependent on a lack of an ongoing Ice Age. Crocodiles cannot exist at 80N if there is 2.9M KM^3 of accumulated ice across Greenland. And more in other remaining glaciers. By definition of enormous extant ice sheets across both Greenland and Antarctica we remain deep within an overall planetary Ice Age.
From this perspective our ongoing predicament is about to become a calamity. Because Ice Ages intensify when the +1.5C vs. 20th Century baseline is reached *within* an ongoing Ice Age (which is why we have never surpassed this mark on a planetary basis since several million years ago).
The cryosphere forms wherever there is snow and ice. There seems to be a disconnect in the mindset of apes that it is based on Latitude. It is not. Why it is cold on top of Everest? Why does it snow on Mauna Loa in June? Because the cryosphere is a fluid concept dependent on ALBEDO and ALTITUDE and not LATITUDE.
Surely latitude helps things along during deep winter, but during summer, the Arctic receives as much insolation as any spot on the planet. The existence of sea ice, which has a declining annual volume totaling less than 1% of the Greenland ice sheet, is a failing constant in a system that had maintained relative balance between heat and heat loss.
Since the early 2000s, the balance of accumulated SWE vs. sea ice outside Greenland as of 4/18 has shifted from about 7.5% to 13.5% (2018). This has resulted in a substantial increase in aerial coverage as well, however the volume uptick for SWE has been way more significant so far.
If this continues we will be at approximately 6,000 KM ^ 3 of accumulated seasonal SWE by this time of year in the 2030s (not every year, but one year, it is likely). Right now we are at about 3,600 KM ^3 vs. 2,200 KM ^3 in the early 2000s.
With substantial aerial snow extent increases evident at our current state, nearly doubling the volume will aggravate existing purples, but also expand coverage substantially. This will mean places like New York City will probably see May snows begin to become regular by the late 2020s. Toronto will be snowing into June. Boston, all year long (JK...................).
Sea ice volume anomalies continue worsening at all times of year, and with GHGs only getting worse and forcing oceanic heating, this shows no signs of stopping. In fact, we likely have another 30-50++++ years of overall oceanic warming baked in TODAY (IMO). But as sea ice volume worsens, the land compensates, which is why despite massive swings in sensible wx now affecting everyone, planetary OVERALL anomalies remain at +1C or so for the duration of the transition.
I do not think we will get above +1.5-2C. Ever. We saw what happened in 2015-2016. The reaction to so much heat in the ocean / water vapor in the atmosphere triggers an ongoing multi-year release in the form of massive snowfalls which affect anything near extant snowpack or sea ice. Of course new snowfalls are possible at distance from the main pack but usually they occur adjacent (which is why it doesn't always snow on Mauna Loa and Mauna Kea -- if they had any substantial assortment of similarly-sized friends, it would. see THE HIMALAYAS).
As heat rises in the oceans, it combines with the extant 2.9 million KM^3 mound of ice in GREENLAND to result in prolific snows beginning first across the Canadian shield, which is downwind of Greenland when oceanic heat forcing is sufficient (normally it is the opposite, but engorged Hadley Cells have a way of their own). When Hadley Cells expand into the mid-latitudes when major SWE is still extant, they act as enormous vacuums for heat, which is thrown north and then equalized and it falls back to the ground in the form of snow over regions to the west, equalizing our predicament due to CO2 and ETC.
This is why the tremendous snow and cold in the US has been accompanied by the tremendous warmth in Europe this spring (IMO). Think of Greenland as the planet's largest air conditioning unit.
As sea ice declines further, we will see the death of the "polar cell" as we used to know it, and the rise of increasing dominant cold-anchored Hadley Cells. These come with STUCK weather patterns as our formerly singular polar vortex multiplies into multiples across the various areas of extant major SWE as the hemisphere heads into spring each year.
As we move forward, this will begin happening more often earlier in the year (October, November, December). But the worst change is going to be in April May and June, as winter makes rapid calendar advances across many regions.
The insane accumulations of SWE will still melt out for the next few years, but the dislocation of the polar vortices into the mid-latitudes from the high Arctic is also going to force enormous cyclonic activity along their eastern peripheries. This is going to drive further and worsening import of oceanic and atmospheric heat into the High Arctic. If it ever goes annually ice-free, god forbid, its capacity as a heat sink will increase EXPONENTIALLY, and IMO we would see a rapid-onset glaciation event begin within the subsequent twelve months over certain regions of North America.
