All posts tagged Melt Pond formation

Arctic Heatwave Forecast to Crush Northern Hemisphere Snow Cover This Week

The Russian side of the Arctic is heating up.

A high amplitude ridge in the Jet Stream is forecast to develop atop the Yamal region of Russia, expand northward over the Kara and Laptev seas, inject a plume of anomalously warm air over the polar region, and then proceed on along the Arctic Ocean shores of Siberia. Beneath this ridge, temperatures over the Arctic Ocean will spike to +1 to +4 C above average while temperatures over land will hit extreme +20 C and higher anomalies.

(Arctic heatwave invades Siberia in the GFS forecast for later this week as depicted by Climate Reanalyzer.)

Arctic Ocean zones are forecast to see temperatures climb above freezing for much of the 80 degree North Latitude zone. Over Siberia, land-based temperatures are predicted to range from the 40s and 50s along the Arctic Ocean boundary and climb to the 60s to 80s in regions just inland.

As temperatures tend to flatten out over Arctic Ocean waters and as permafrost zones in Siberia are used to far cooler readings during Northern Hemisphere Summer, the predicted heatwave is likely to have some rather strong impacts should it emerge. Most notably, snow cover over remaining land and sea ice is expected to see a rather extreme reduction over the next seven days. In other words, GFS forecast models show Northern Hemisphere snow cover basically getting crushed:

(Massive reduction in Northern Hemisphere [NH] snow cover predicted coincident with Siberian Heatwave later this week. Left frame shows current NH snow cover. Right frame shows predicted NH snow cover for Tuesday, June 9. Image source: Climate Reanalyzer.)

Sparse remaining snow cover in Northeast Siberia along the East Siberian Arctic Shelf coastal zone is expected to be pretty much wiped out. One foot average snow cover along the shores of the Laptev and Kara seas is also expected to melt. And a broad section of remaining snow upon the sea ice is predicted to retreat away from the North Polar region — receding back toward the final haven near Greenland.

Snow is important for spring and summer-time Arctic temperature moderation due to the fact that it provides insulation to sea ice and permafrost as well as serving as a reflective, high-albedo surface that bounces back some of the incoming heat from the 24-hour seasonal Arctic sun. Snow melt, on the other hand, serves to form albedo-reducing melt ponds over the Arctic Ocean sea ice during summer. A critical factor in late season melt forecasting in which more June melt ponds tend to mean lower sea ice totals by end season. In addition, snow melt fills permafrost zone rivers with above-freezing waters that then flow into the Arctic Ocean — providing yet another heat forcing to the sea ice.

Conditions in Context

This weekly trend and forecast is consistent with an ongoing tendency during 2015 for strong ridge formation and warm air slot development over both Alaska and the Yamal region of Russia. The high amplitude ridges also likely have teleconnections with larger weather patterns such as El Nino in the Pacific, the warm water pool (hot blob) in the Northeast Pacific, and record low sea ice extents continuing for most of Northern Hemisphere Spring. Observations that are also consistent with the predictions made by Dr. Jennifer Francis that are a direct upshot of polar amplification set off by human-caused warming of the global climate system.

(GFS model forecast as depicted by Earth Nullschool showing ridge Northwest Territory, trough Greenland and North Atlantic, ridge Kara and Laptev region of Siberia. A dynamic that may be the result of teleconnections set off by factors related to human-caused climate change. Image source: Earth Nullschool.)

It’s worth noting that many of these factors are self reinforcing. For example, more sea ice melt results in higher amplitude wave formation in the Jet Stream. Higher amplitude wave formation in the Jet Stream transports more warmth to the Arctic environment, resulting in more sea ice and snow melt which in turn weakens the Jet Stream further. A longer-term amplifying feedback of Arctic carbon release may also be in play (hinted at by an overburden of both CO2 and methane in the local Arctic atmosphere), which would also contribute to the conditions we now observe.

A final feedback, this one somewhat negative, occurs as a result of Greenland Ice Sheet (GIS) melt. Large cold, freshwater outflows from GIS into the North Atlantic result in localized cooling in that region. This feedback (also related to AMO weakening) enhances trough formation throughout the North Atlantic region adjacent to Greenland and the Canadian Archipelago. A final potential teleconnection to the ridges we see forming over both Yamal and the Alaska/Northwest Territory zone.

Links:

Climate Reanalyzer

Earth Nullschool

Heat Wave Forecast for Russia

Rapid Arctic Sea Ice Loss Linked to Extreme Weather

Tracking for Early Season Melt Pond Formation at The Arctic Ice Blog

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by robertscribbler on June 2, 2015 • Permalink

Posted in Climate Change

Posted by robertscribbler on June 2, 2015

https://robertscribbler.wordpress.com/2015/06/02/arctic-heatwave-forecast-to-crush-northern-hemisphere-snow-cover-this-week/

2012 Record Challenged as 40% of Greenland Ice Sheet Surface Melts on June 17th

Yesterday, 40% of the surface of Greenland melted.

It was still mid-June, yet a month before melt values typically peak. But a persistent high pressure system over Greenland, a rapidly melting Baffin Bay and warm winds riding up the west coast were enough to spur a surface melting event that shoved melt coverage firmly above the two standard deviation threshold and into record range.

(Greenland Melt Extent as of June 17, 2014. Image source: NSIDC.)

Temperatures along the west coast of Greenland and on through the southern ice-covered tip ranged between 30 and 55 degrees Fahrenheit, while 30-43 degree readings surrounded much of the periphery. Warm winds and rain to mixed precipitation accompanied a moisture-laden storm emerging from Baffin Bay and passing over the western ice sheet to add further and extreme early season melt pressure.

The warm storm and rains compounded already rapid melt pond formation along Greenland’s southwestern coasts. Large blue ponds varying between .5 to 3 kilometers in width had already formed over southern and western sections of the ice sheet by June 16, before they were covered in clouds and squally wet weather on June 17th. By today, the clouds cleared as the passing storm moved on to reveal melt ponds further swelled by a combination of warmth and wet weather:

(Large expanse of melt ponds near the outlet to the Jacobshavn Glacier on June 18, 2014. The smallest blue dots represent glacial melt ponds of about 300 meters in width. The largest exceed 3 kilometers at the widest point. Image source: LANCE-MODIS.)

Melt ponds add heat amplification to the glacier surface by reducing albedo even as they provide melt drainage to the glacial base. Floods of water from melt ponds add to glacier speed and buoyancy by reducing friction at a moving glacier’s base and by flooding geographic low points beneath the glacier. Melt ponds also reduce overall ice sheet integrity by permeating the ice with holes and fractures.

The Jacobshavn Glacier in the satellite shot above is Greenland’s fastest. It is now involved in a very rapid rush toward the ocean at a rate of 46 meters per day. A rush that has been facilitated in recent years by a major proliferation of melt ponds during summer time.

During extreme events, melt ponds can combine and over-top or break ice dams in dangerous glacial outburst floods. It is worth noting that Greenland melt pond proliferation has not yet reached a threshold for high risk of such events. But the now decade-long proliferation of melt ponds over the ice sheet surface during summer time remains a troubling occurrence.

40% melt coverage in mid June is an extraordinarily high number. Last year, melt coverage peaked at 47% in late July with June values approaching the high 20s in late June. July of 2012 saw a 97% melt coverage — an event last seen about 120 years ago and one that is, unfortunately, likely to be repeated soon under current human heat forcing. It is worth noting, however, that the record year of 2012 saw Greenland melt coverages periodically exceeding 40% from mid-to-late June.

(Greenland melt coverage on June 17 of 2014. Image source: NSIDC.)

Early melt and proliferation of melt ponds along with persistent high pressure systems over Greenland tend to have a compounding effect that amplifies over-all melt coverage. Low mists and clouds tend to form during such conditions, trapping heat near the ice surface even as albedo over the ice sheet falls due to wide-scale melt pond formation.

Though yesterday’s melt coverage is an early challenge to melt levels seen during 2012, current conditions would have to both persist and intensify for the broad extent of melt seen during late June and through July of 2012 to show a rough repeat. That said, a 40% melt coverage on this date is a record-challenging level that bears watching.

Links:

NSIDC

LANCE-MODIS

Greenland Undergoing Record 120 Year Melt

The Glacial Megaflood: Growing Glacial Outburst Flood Risk

Hat tip to Andy from San Diego