Po­lar Ice Melt­ing Far Faster Than Of­fi­cially Pre­dicted

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Like ev­ery­thing else re­lated to global warm­ing and cli­mate change, at both ends of the globe, po­lar ice is melt­ing far faster than of­fi­cially pre­dicted.

In the Arc­tic

In the Arc­tic, warm­ing pro­jec­tions are now so dire that cur­rent of­fi­cial cal­cu­la­tions sug­gest the Arc­tic could be com­pletely ice-free by 2040 (un­of­fi­cially it will likely be ice-free much sooner – per­haps even this year).

Though that is only 22 years away, the melt­ing rate on a daily or even monthly ba­sis is still slow enough that in most places in the Arc­tic it is usu­ally hard for ca­sual ob­servers to see how bad the warm­ing trends are. This year, how­ever, with the months of De­cem­ber through March af­fected by a se­ri­ous heat wave never seen be­fore, the melt­ing is be­com­ing a lot eas­ier to spot.

One of the best ex­am­ples of this is seen in Alaska’s De­nali Na­tional Park. There, the glaciers are melt­ing faster than dur­ing the past four cen­turies.

Be­cause of global warm­ing, snow on the park’s Mt. Hunter is melt­ing at a rate over 60 times greater than dur­ing the sum­mer be­fore the in­dus­trial pe­riod started – about 150 years ago. The rate is so rapid that ac­cord­ing to a new study pub­lished by lead au­thor Do­minic Win­ski in the Jour­nal of Geo­phys­i­cal Re­search: At­mos­pheres (a jour­nal of the Amer­i­can Geo­phys­i­cal Union), more snow now melts on Mt. Hunter than at any time dur­ing the past 400 years.

Win­ski is a glaciol­o­gist at Dart­mouth Col­lege in Hanover, New Hamp­shire.

Based on new ice-core sam­ples taken from Mt. Hunter’s sum­mit, sum­mers there are now run­ning a min­i­mum of 1.2-2°C (2.2-3.6°F) warmer than at the same time of year in the 18th, 19th and early 20th cen­turies. The warm­ing at the sum­mit is about twice that which oc­curred at sea level in Alaska dur­ing the same time pe­riod.

Those cores were drilled at the sum­mit plateau of Mt. Hunter, at a level of 13,000 feet above sea level. The sam­ples pro­vide a graph­i­cal means of un­der­stand­ing past weather pat­terns, as the darker ice bands with­out bub­bles sug­gest times when gla­cial snow melted in the sum­mers and then re-froze. When a given year pro­duced more melt events (and more dark ice bands), that means the sum­mer was warmer.

Based on the data ob­served this way, the re­search team de­ter­mined that melt events are hap­pen­ing 57 times more of­ten than 150 years ago. There were in fact only four melt event years be­fore 1850. What that sug­gests is that the to­tal melt­wa­ter pro­duced in the cores in re­cent times is 60 times what it was dur­ing the pre­vi­ous 150 years.

This also ties in with the hot­ter tem­per­a­tures cur­rently be­ing recorded in the trop­i­cal Pa­cific Ocean. That area, like else­where in the world, has seen sig­nif­i­cant tem­per­a­ture in­creases since the mid-1950s as a re­sult of in­creased green­house gas emis­sions. The re­searchers be­lieve the warm­ing trop­i­cal Pa­cific is cre­at­ing warm air cur­rents that are mov­ing to the earth’s po­lar re­gions. With few high moun­tain ranges in the way near the trop­ics, the air can mi­grate faster and far­ther than had pre­vi­ously been be­lieved. That is part of why the poles seem to be see­ing far more ex­treme heat – and re­sul­tant glacier melt­ing – than re­gions closer to the equa­tor.

Ac­cord­ing to Luke Trusel, a glaciol­o­gist at Rowan Univer­sity in Glass­boro, New Jersey, who saw the Mt. Hunter study’s re­search but was not part of the work, “this adds to the grow­ing body of re­search show­ing that changes in the trop­i­cal Pa­cific can man­i­fest in changes across the globe. It’s adding to the grow­ing pic­ture that what we’re see­ing to­day is un­usual.”

In the Antarc­tic

While the Arc­tic has been well-known to be in trou­ble from global warm­ing, sci­en­tists were see­ing a far more sta­ble scenario in the Antarc­tic. There, the ice seemed to be melt­ing slower and more er­rat­i­cally. There were still prob­lems there but nowhere near the mag­ni­tude of those in the Arc­tic.

A new study re­vealed at the end of March 2018 has un­for­tu­nately changed all past think­ing on that. Based on the data, it looks like Antarc­tica will likely soon be­come the big­gest source of sea level rise in the world. That puts the cur­rent front-run­ner from that list, Green­land, into the num­ber two slot.

The rea­son for this sur­prise is that up un­til now the rate of melt­ing of Antarc­tic ice sheets was es­ti­mated solely by look­ing from above. It was as­sumed that the sun and warmer air from above, along with warmer wa­ter ocean cur­rents lap­ping the edges of the sheets, were the main con­trib­u­tors to their melt­ing.

That as­sump­tion is wrong, ac­cord­ing to re­searchers from the Univer­sity of Leeds, who con­ducted the new study. It turns out that the an­chor ice for the sheet, which runs un­der the ice sheet, is melt­ing at a much higher rate than the part above wa­ter. The melt­ing rate for the un­der­wa­ter part of the ice is, of course, ul­ti­mately what de­ter­mines sea level rise, and that’s a big prob­lem.

Some of the ice in the Antarc­tic runs as deep as two kilo­me­ters (1.2 miles) un­der­wa­ter. That is a lot of ice to be melt­ing so fast.

The trick that al­lowed the re­searchers to dis­cover the er­ror in cal­cu­lat­ing melt­ing rates was map­ping the “ground­ing lines” that sep­a­rate the top part of the ice sheet with the un­der­belly be­low. The re­searchers found a new way to map those ground­ing lines and an­a­lyze just how fast they were re­treat­ing across the Antarc­tic sheets.

Ac­cord­ing to the study’s lead au­thor, Hannes Kon­rad, they learned that warm­ing ocean wa­ters have in five years eaten away an area of un­der­wa­ter ice ap­prox­i­mately the size of Greater Lon­don. The ice has ei­ther com­pletely melted or is drift­ing to­ward the warmer ocean wa­ters north­ward of the Antarc­tic re­gion, where it will even­tu­ally break into smaller pieces and then melt com­pletely.

The re­searchers also found that ap­prox­i­mately 25% of the West Antarc­tic glaciers are melt­ing at a faster rate than the ice stream did at the end of the last ice age. That raises se­ri­ous con­cerns, since at that time – 20,000 years ago – sea lev­els were about 120 me­ters (394 feet) lower than they are to­day.

The team is try­ing to come up with ex­act pre­dic­tions of the av­er­age rate of melt­ing of the Antarc­tic sheets. Also of in­ter­est are the com­pound­ing ef­fect and cor­re­spond­ing melt­ing ac­cel­er­a­tion that hap­pen as the ocean wa­ters warm in gen­eral. That will get more se­ri­ous as global warm­ing it­self in­creases.the grow­ing warm­ing of the globe will only make all this worse as time goes on, warm­ing the trop­ics, melt­ing the Arc­tic, un­der­min­ing the lower part of the Antarc­tic ice sheets and caus­ing ris­ing seas across the planet. It is fur­ther ev­i­dence of the ur­gency with which the en­tire world needs to re­spond to this cat­a­strophic world­wide prob­lem.

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