Friday, 2 September 2016

Robertscribbler on Endless Hot Summer of 2016

Endless Hot Summer of 2016 — Heavy Arctic Sea Ice Losses, Record Temps for Alaska and Hermine’s Rains Barreling In


1 September, 2016


From the Arctic leveling yet another challenge to all-time record lows for sea ice, to a ridiculously long spate of hotter-than-normal temperatures for Alaska, to Hermine — which appears to be readying to drop 20 inches of rain over parts of the Southeast — there’s a ton of concerning climate news today. Let’s get to it.
Storms, Mega-Dipoles, and Shattered Sea Ice

A few weeks ago, big storms of near-record intensity started ripping through the Arctic. These storms saw numerous pressure dips into the 960-millibar range. These severe systems raked the ice with gale-force winds, heavy seas, and rainfall. A vulnerable ‘arm’ of ice extending out from the central Arctic toward Wrangel Island began to disintegrate under these multiple insults.

Melt Lobes
(The two frames above provide a good visual of the most vulnerable Arctic Ocean melt regions for early to mid-September. These primarily compose the Siberian side of the Arctic and run on toward the Pole. A mostly detached and storm-battered region of sea ice north of Wrangel Island [left frame] is likely to see continued losses through mid-September. At the same time, another vulnerable lobe of ice extending from the Pole to the Laptev Sea [right frame] is seeing substantial thinning. As southerly winds pick up later this week over the Barents and Greenland Seas, the Atlantic side of the Arctic [lower right portion of right-hand image] may also take a final blow or two before refreeze starts to kick in. Images provided by: LANCE-MODIS. Date for images: September 1, 2016.)

Meanwhile, another melting wedge running out from the Pole toward the Laptev Sea was increasingly wracked, showing severe losses along the ice edge even as large openings expanded, stretching in toward the Pole. As a result, major late-season drops in Arctic sea ice area and extent measures began to show. Unfortunately, the damage had only just begun.
Last week, this stormy pattern saw the added wrinkle of a strong high-pressure system in the range of 1040 mb intensity forming over the Chukchi and Beaufort Seas. This new system created an extreme pressure gradient between itself and the storms raging near the Pole and on the Atlantic side. Expert Arctic sea ice observer Neven aptly coined this condition the 2016 Mega-Dipole.

Neven's Mega-Dipole
(Neven’s Mega-Dipole featured a burly high-pressure system over the Pacific side of the Arctic as strong storms continued to rage across the Atlantic side on August 29th. The combined force of these systems helped further damage the already weakened sea ice as warm winds blowing between them pulled heat up from Siberia, generating a late-season temperature spike over the Arctic Ocean. Image source: Earth Nullschool.)

Strong winds blew between the juxtaposed low- and high-pressure systems. This convergence sucked an intense pulse of warm air up from the south, not only providing a severe blow to the ice from gales and waves, but also injecting a surge of late-season heat into the High Arctic. In addition to the damage being done to the two melt arms, the whole of the remaining contiguous ice was driven in one big push toward the Canadian Arctic Archipelago — a shove that has now likely resulted in the complete separation of the thinned near-Wrangel ice from the pack even as large polynya (or holes) opened up within 10 kilometers of the Pole.

Late Season Arctic Heat Spike
(A late-season temperature spike in the region above 80° North Latitude is helping to generate a surge in ice losses during early September. Image source: DMI.)

All this pushing and shoving and storming and low and high pressuring in the context of never-before-seen Arctic warmth has brought most of the major measures within range of beating out 2007 as second-lowest extent on record by mid-September. Meanwhile, a few of the measures are now making serious challenges to the 2012 record-low marks.
Over the coming days, the various high-pressure systems are predicted to shift more toward the Siberian side of the Arctic. Meanwhile, storms are expected to gather around Greenland, with some hitting the 970 to 980 mb range as they circulate up from the North Atlantic. Warm air is expected to funnel in from the Barents and Greenland Seas even as the region north of Greenland starts a cooling trend.
Sea Ice Extent Measures
SSMI
(Japan’s JAXA monitor shows [top left] sea ice extent beating out 2007 in the daily extent measure. Meanwhile, DMI’s EUMETSAT-based monitor shows [top right] extent falling to near the 2012 line. Sea ice area in NERSC’s SSMI monitor [bottom] over recent days comes uncomfortably close to the 2012 line.)

This hot-cold juxtaposition combined with ongoing pressure from storms, winds, and waves should continue to damage and expel the most vulnerable sections of ice in the near-Pole region and on toward the Laptev as well as the detached ice floes near Wrangel Island. Additional losses in the range of 150,000 to 300,000 square kilometers or more over the coming seven days are entirely possible. If this happens, it would be a rather severe rate of loss for early September all on top of a year that, on average so far, has seen lowest-recorded sea ice extents for the January-to-August timeframe and remains on track to hold that low mark through year-end.
An Amazingly Hot Year for Alaska

We should be very clear that despite all the storms and other weather drama going on over the Arctic Ocean, the primary cause for severe sea-ice losses is a record-hot world in which a lion’s share of the temperature rise is occurring over the far northern latitudes. And not too far from the melting Arctic sea ice, another Arctic region is also getting a big dose of this record heat.
This year, Alaska appears set to exceed all previous marks for warmest temperatures ever recorded during an annual period for the state:
Alaska with more days in the above normal tercile in 2016 that either 2014 or 2015 – the 2 warmest years on record.
(Through August 27, Alaska had experienced zero cooler-than-typical days, 22 days of relatively normal temperatures, and 218 days in which temperatures were in the top third of all daily averages. It’s a record that makes previous all-time hot years 2014 and 2015 look somewhat cool by comparison. Image source: Climatologist Brian Brettschneider.)

As climatologist Brian Brettschneider recently found, above, the number of days featuring temperatures in the top third of measurements included nearly nine out of ten of all days so far during 2016 and through August 27th. This extreme Alaskan heat has already exceeded the number of warmer-than-normal days during record-hot years 2014 and 2015. With four months in 2016 still remaining, and with the Arctic Ocean opening up to its north, it appears that Alaska is about to blow these previous record years out of the water.
Alaska in hot water
(Sea-surface temperatures surrounding Alaska are between 3 and 5 degrees Celsius above average. Such extreme ocean heat should help keep temperatures abnormally warm over the state for at least the next couple of months and continue to add to a period of record heat during 2016. Note that the graphic above shows temperature departures from normal ranges, not absolute temperature values. Image source: Earth Nullschool.)

La Niรฑa is settling in, though. This would normally provide some hope that temperatures in Alaska might start to fall off a bit, but right now, the local ocean waters surrounding Alaska are extraordinarily warm. It’s as if the Pacific ‘hot blob’ that plagued the U.S. west coast in 2014 and 2015 has shifted north toward Alaska in 2016. This climate change-related warm-water feature is likely to continue to create a warm surface temperature bias for the state over the next couple of months.
20 Inches of Rain Possible for Parts of the Southeast

Moving south and away from the various heating and melting in the Arctic, we find yet another big rainstorm brewing in the moisture-stacked atmosphere of the Gulf of Mexico. In this case, unlike the big deluge that roared through Louisiana during early August, this collection of towering thunderheads has a name — Hermine.
Hermine 4
(Hermine, which may produce severe flooding over the U.S. southeast in the coming days, barrels toward Florida in this National Hurricane Center satellite animation.)

Punching up to minimal hurricane status early in the afternoon (EST) on Thursday, Hermine is predicted to make landfall along the big bend of Florida (pushing in 3-8 foot storm surges), track north into Georgia and then run up along coastal South Carolina, North Carolina and Virginia. Along this path, 4-10 inches of rainfall are expected with local amounts hitting as high as 20 inches.
To this point, The National Hurricane Center notes:
Hermine is expected to produce storm total rainfall accumulations of 5 to 10 inches over portions of northwest Florida and southern Georgia through Friday, with possible isolated maximum amounts of 20 inches. On Friday and Saturday, Hermine is expected to produce totals of 4 to 8 inches with isolated maximum amounts of 10 inches possible across portions of eastern Georgia, South Carolina, and eastern North Carolina through Saturday. These rains may cause life-threatening flash flooding.
As with past rain-bomb events this year, Hermine is churning through a record-hot atmosphere and feeding on overall record-high moisture levels. Sea-surface temperatures over the Gulf of Mexico and particularly over the Gulf Stream region of the Atlantic near the eastern seaboard are extraordinarily hot. Ocean surfaces off coastal Virginia, for example, now rival those along the eastern Gulf at near 30 degrees Celsius (86 F). The result is that a ton of storm energy in the form of heat and moisture is blanketing a big swath from Florida to the U.S. northeast. In this heat- and moisture-rich environment, even the high forecast rainfall amounts have a potential to be exceeded.
Hot Water Gulf Stream
(Ocean temperature and currents map for 8/30/16. Water temperatures in the Gulf Stream off the U.S. east coast are near 30 C [86 F] or about 4 C hotter than normal. This means there’s almost as much potential storm fuel for a hurricane off the eastern seaboard as there is in the northeastern Gulf of Mexico — fuel that can both provide energy for extreme rainfall events related to Hermine and for a possible rapid reintensification. Image source: Earth Nullschool.)

Moreover, Hermine is predicted retain a degree of strength over land due to this fuel even as it is expected re-emerge over water along the North Carolina sounds and then track toward the hot Gulf Stream. Along this track, the storm is expected to restrengthen and lash coastal North Carolina, Virginia, Delaware and New Jersey before it skirts Long Island and Massachusetts. Given the hot ocean waters, some models even show Hermine bombing into a significant storm with ECMWF model runs earlier today highlighting a potential for a 969 mb storm center off Delaware on late Saturday.

Fortunately, the storm center is currently predicted to remain offshore after re-emerging over open waters on Saturday. However, the large circulation of the system means that any reintensification will likely see some of the storm’s related rain bands swirling out over the mid-Atlantic and northeast coasts.
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So from big sea ice losses to record heat in Alaska, to what’s shaping up to be another extreme rain event for the U.S. southeast, the climate hits just keep on coming. It’s all a part of the context of climate change that’s been steadily settling in over the past few decades, which paints a rather obvious picture of ongoing climate shifts and alterations to expected weather patterns — to include the loss of sea ice, the intensity of heat over Alaska and the severity of rains falling out during storms like Hermine.
Links:

Hat tip to Colorado Bob
Hat tip to DT Lange
Hat tip to DavidlWindt
Hat tip to Jay M
Hat tip to the Arctic Sea Ice Forum
Hat tip to Greg



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