Warm, Storm-Force Winds Blowing From the Equator Flip West Antarctic Winter to Summer

In a record-hot world, there’s a lot of lower-latitude heat just waiting for a weakness in the increasingly feeble Jet Stream to make a big poleward rush. Such was the case today as an intense wave of warmth exploded up from the Equatorial region and began to spread summertime temperatures over sections of West Antarctica — technically still in the grips of the Southern Hemisphere’s winter season.

image

(A surge of heat breaks over West Antarctica on September 2nd, 2016, pushing air temperatures over vulnerable coastal glaciers and ice shelves near or above the melting point [0 degrees Celsius]. Image source: Earth Nullschool.)

The warm winds began their southward turn about a thousand miles west of coastal South American and along the 20 degrees south latitude line. Tapping hot, tropical air, the winds then ran over hundreds of miles of open ocean — following the arch of a bulging ridge in the Jet Stream. These winds then gathered, howling through the Southern Ocean with storm force gusts of 50 to 65 mph before delivering their payload of abnormal warmth to West Antarctica.

Larsen C Ice Shelf Experiencing Above-Freezing Temperatures in Winter

Along the coast of Ellsworth Land, temperatures have risen to near the thawing point (0 degrees C), in winter, in a region that typically sees -2 to -3 C readings during summer. Temperatures that are 15 to 23 C above average (27 to 40 F) now range all over the Antarctic Peninsula and nearby areas of West Antarctica. Perhaps most dramatic are the 1.5 C readings coming from sections of the C region of the Larsen Ice Shelf bordering the Weddell Sea. There, downslope hurricane-force winds howling over the shelf are helping to spike local temperatures even as sea ice in the Weddell is splintered and shoved away from the Larsen C edge.

West Antarctic Heatwave

(A wave of 20+ C [36+ F] above-average temperatures blankets the vulnerable glaciers of West Antarctica on Friday, September 2nd. This pulse of tropical warmth is enough to drive readings over Antarctica to summertime or warmer ranges during winter, with some regions that typically experience below-freezing temperatures year-round nearing or exceeding the thawing point. Image source: Climate Reanalyzer.)

Larsen C is of particular interest due to a large crack spreading through its main body, threatening to break off a Connecticut-sized chunk of ice and disrupt the stability of the larger ice shelf. The most northerly of the remaining large Antarctic Peninsula ice shelves, this towering mass of frozen water serves to buttress a number of large Antarctic glaciers. Its loss or destabilization would allow these glaciers to increase their speed of ocean discharge and in turn, speed the rate of global sea-level rise. Needless to say, this combination of above-freezing temperatures during winter and hurricane-force winds won’t help to stabilize this now more than 120-kilometer long and hundreds-of-feet-deep crack.

Antarctic_surface_temperature

(Differences between average summer and winter temperatures over Antarctica. For sections of West Antarctica near the Antarctic Peninsula, Friday through Sunday will see temperatures more typical to Antarctic summer — during late winter. Image source: European Center for Medium-Range Weather Forecasts.)

A Winter of West Antarctic Heat — Larger South Pole Warm-up on the Way?

More broadly, warming this region to above freezing for extended periods is a concern among glaciologists. In the past (during the Pliocene and Miocene), when atmospheric CO2 levels have hit a range of 390-405 parts per million or above, West Antarctica (and ultimately East Antarctica) experienced warmth which resulted in seas that were many feet and meters higher than today. With atmospheric CO2 readings likely to average near 405 ppm during 2016 (or total greenhouse gas levels in the range of 490 ppm CO2e), it appears that frequent periods of summer-like temperatures and related increasing melt pressure are now possible during polar winter.

Over recent months, this section of Antarctica has been clobbered repeatedly by such spates of above-normal temperatures. Back in June, an odd Jet Stream excursion (gravity wave) pulled a big pulse of Equatorial heat over West Antarctica. Today’s event is just one of a number of recent big warm air invasions into this highly vulnerable zone.

CFSv2 Hot South Pole Summer

(More severe melt stress for Antarctic glaciers? NOAA’s CFSv2 model shows a ridiculously hot South Pole summer may be on the way. Side note — over the past year or so this forecast model has run somewhat cooler than actual temperatures for the Arctic region. Image source: NOAA.)

Taking this most recent warming event into context and looking forward into late 2016 and early 2017, at least one global forecast model is predicting a period of severe Antarctic warming during this time. NOAA’s CFSv2 model, for example, finds a very extreme Antarctic temperature spike emerging over pretty much all of Antarctica during the late Southern Hemisphere summer and early fall months of 2017.

Links:

Earth Nullschool

Climate Reanalyzer

European Center for Medium-Range Weather Forecasts

Another Blow to Glacial Stability

NOAA

Weather data provided by the Global Forecast System Model

Antarctic Heat Heralds Hottest September in the NASA Record

September 2014 Hottest on Record

(Global temperature anomaly map for September of 2014. Note extraordinary bands of very strong positive temperature anomaly ranging the globe with hottest zones at or near the poles. Image source: NASA GISS.)

Another hottest month on record for the global climate. And this one is a bit of a doozey.

According to NASA GISS, September of 2014 saw global surface temperatures that were 0.77 C hotter than the 20th Century average. This record beats out 2005 by a rather strong 0.04 C margin and represents the 3rd month in the GISS record for 2014 that was either the hottest or tied for the hottest (May, August and September).

Ocean surface heat and anomalous warmth at the poles were deciding factors for the new September record with very few regions of the global ocean surface showing cooler than average temps and with extraordinary heat at the poles, especially in Antarctica. This southern polar zone experienced average monthly temperatures as much as 8.7 above the global average across a relatively broad zone. Both East and West Antarctica observed this very strong polar amplification with East Antarctica experiencing the peak anomalies.

zonal anomalies map september 2014

(Zonal anomalies by Latitude in the NASA GISS measure. Image source: NASA GISS.)

The zonal anomalies map for September of 2014 showed no latitudinal zone experiencing cooler than 20th Century average conditions. A rather extraordinary feature considering most months show cooler than 20th Century average conditions along at least some latitudes.

Most extreme heating occurred at or near the poles with the 75-80 degree South Latitude zone showing an extraordinary +3.4 C departure from the global norm and the 80-90 degree North Latitude zone showing a strong +1.75 degree positive anomaly.

The only zone showing near 20th Century average temperatures was the heat sink region of 55 to 60 degrees South Latitude in the Southern Ocean. In this climate region a strong storm track combines with an expanding fresh water wedge issuing from melting Antarctic glaciers to force down-welling and atmosphere to ocean heat capture. A heat capture that was alluded to in a recent scientific paper which found the upper Southern Ocean contained between 24 and 55 percent more heat than expected.

This heat sink region, featuring an expanding fresh water wedge has been instrumental in somewhat higher than normal Antarctic sea ice totals. An impact that is, ironically, driven both by Antarctic continental ice melt together with an increasing storminess in the Southern Ocean and waters more heavily laden with salt issuing from the equatorial zone. A highly unstable confluence that results in local surface cooling as the ocean takes a heavy dose from the human riled heat engine.

Conditions in Context

No El Nino yet, despite two warm Kelvin waves and somewhat favorable atmospheric conditions throughout the months of August and September. But sea surface temperature in the Equatorial Pacific region remain somewhat hotter than normal — bending toward the warm side of ENSO neutral. Overall ocean surface warmth, however, was extraordinary throughout September, pushing well above the global average and ranging, in GFS models, from 0.7 C to 1.2 C above the already hotter than normal 1979 to 2000 average.

Overall, three more record or near record hot months would put 2014 in serious contention for hottest year on record (2014 is running 0.65 C hotter than average, the global record is 0.67 C above average for 2010). A rather odd result considering we still see no El Nino and almost every recent hottest year has been spurred on by this powerful atmospheric variability driver. A record hot year in 2014 with no El Nino could well be an indication that the human forcing is beginning to over-ride natural variability and that the ENSO signal, though still very powerful, is becoming more and more muted by an increasingly substantial human heat forcing.

Links:

NASA GISS

It’s Worse Than We Thought — New Study Finds that Earth is Warming Far Faster Than Expected

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