Tuesday, 1 November 2016

A Halloween ice melt in Greenland?

This is just to remind us of what is most important – and it’s not a stolen election

Hot Climate Conjures Trio of Nasty Halloween Tricks — Heatwaves, Record-Low Sea Ice, Fall Greenland Melt


31 October, 2016

With each passing year, the effects of human-caused climate change become more and more visible. But for some reason, Halloween appears to be a preferred time for the emergence of various hothouse hobgoblins. In 2012, the Atlantic seaboard was reeling after a vicious strike from Hurricane Sandy. Over the past three years, powerful North Atlantic storms had begun to build at this time of year, setting sights on the UK and Europe. This year, as a hurricane-force low roars toward the Aleutians, the nastiness comes in the form of weird heatwaves, record-low global sea ice coverage, and hints of odd late-fall Greenland melt.
Record Heat Strikes Arctic, U.S.

NASA’s Gavin Schmidt has been warning for months that 2016 will be a global scorcher for the record books. Nowhere has this heat been more apparent than in the Arctic. Halloween only serves to reinforce the rule as today’s temperature departure for the entire region above 66 degrees north latitude hit 5.94 degrees Celsius above average:

global-anomaly-map-halloween
(The extreme Arctic warmth that has already caused so much in the way of climate disruption remains firmly entrenched on Halloween. Image source: Climate Reanalyzer.)

Yesterday, those temperatures exceeded the 6-C-above-normal mark. And later this week, temperatures for the region could approach 6.3 to 6.5 C above average.
These are the average departure ranges for the entire area above the Arctic Circle. Localities within that broader region are hitting as much as 20 C (36 Fahrenheit) or more above average on an almost daily basis, bringing temperatures more typical of the Arctic during late summer than in the middle of fall.
In Barrow, Alaska, Jonathan Erdman reports that Saturday saw the proverbial mercury hit 41 F. This temperature, at about 26 degrees above average, smashed the previous daily high and pushed the latest day Barrow has ever seen a reading above 40 F fully one week forward.
record-temperatures-us
(Daily high and high min temperature records for the U.S. were broken at an alarming rate over the past week, producing a Halloween heatwave. Image source:  NOAA.)

Farther south, the lower 48 is experiencing what Bob Henson over at Weather Underground is calling the Halloween Heatwave. Over the past week alone, nearly 300 daytime high marks were broken. But the measure of record-high minimum temperatures — a key indicator of human-forced warming — is off the charts with 639 total records smashed over the past seven days.

What’s even more odd is a near-total lack of cool temperatures. Bob Henson finds that:
Even more noteworthy than the degree of warmth is the lack of widespread autumn chill. For example, Minneapolis has yet to dip below 36°F as of Friday, October 28. That doesn’t look likely to happen before at least next weekend (November 5 – 6). In records going back to 1873, the latest Minneapolis has ever gone before seeing its first 35°F of the autumn is November 1, way back in 1931. The city’s latest first freezewas on Nov. 7, 1900.

Reinforcing this point, NOAA finds that over the past week just 40 record low high temperatures were achieved (about one-seventh the number of record highs). Meanwhile, record low nighttime temperatures were only achieved in six instances, about one-one-hundredth the rate of record high minimum temperatures! Furthermore, at no location in the U.S. for this week, this month, or even this past year has snow depth achieved a new record high. That’s a pretty ridiculous indicator that the U.S. has reached a rather disturbing climate threshold for heat overall.

Record Low Global Sea Ice Coverage

Even as new warm temperature records were being set with amazing frequency across parts of the Northern Hemisphere, another duo of worrisome indicators were popping up in the Arctic and Antarctic. In the Arctic, the ocean has been loaded up with a ridiculous amount of heat. This heat is preventing the ocean from refreezing, creating various regional barriers to ice formation as the waters ventilate this excess heat into the atmosphere. As a result, Arctic sea-ice extent record lows continue to deepen.
Fall 2016 sea ice extent values — which have consistently lagged behind average daily refreeze rates for most of the season — are now more than 600,000 square kilometers below the previous record set during 2012. It’s, quite frankly, an insane shattering of the previous record low value; a warming-spurred melt that has erased an area of sea ice coverage nearly the size of Texas in just four years.
arctic-sea-ice-jaxa
(Current Arctic sea ice extent values are 6.92 million square kilometers [October 30]. This is 600,000 square kilometers below the previous record low set on the same day during 2012. It is also about 3 million square kilometers below average values seen for this day back during the 1980s. Image source: JAXA.)

The Washington Post this past Friday provided a good article explaining the dynamics involved and highlighted predictions by prominent Arctic researchers that ice-free summers could occur by the 2030s. This is a marked departure from earlier estimates that had put off ice-free summers until the 2050s or even the 2080s. However, it’s worth noting that there’s a decent risk that even these more advanced predictions may prove conservative in the end. Under current trends, ice-free periods for the Arctic Ocean during summer become statistically possible as soon as the early to mid 2020s, and a strong outlier year — where an abnormally warm winter is followed by an abnormally warm summer — could produce such a result even sooner.

On the other side of the world, the Antarctic is also experiencing record-low ranges for sea ice extents. There, regional temperatures are near 4 C above average for the entire Antarctic. Though these departures are not as extreme as those currently seen in the Arctic, they are certainly enough to impact sea ice. Now, sea ice extent values there are at their second lowest ever recorded in the daily measure.

Over recent years, storminess in the Southern Ocean and an expanding fresh water lens running out from Antarctica due to glacial melt have generated a seemingly contradictory expansion of sea ice near Antarctica. This happens because fresh water at the ocean’s surface acts to deflect heat toward the ocean bottom, a feature that has enabled the melting of various glacier undersides in Antarctica. But as the global ocean and atmosphere warm in general, larger melt outflows are necessary to reinforce this surface freshwater lens effect. As a result, we appear to be experiencing a seesaw in Antarctic sea ice extent as a pulse of atmospheric and ocean warming overrides the impact of initial fresh water lensing.
global_sea_ice_extent_zoomed_2016_day_301_1981-2010
(MASIE global sea ice extent shows a severe negative departure through October 28, 2016. Image source: Sunshine Horus.)

The combination of significant sea ice losses in the north and second-lowest sea ice extents in the south has resulted in a global sea-ice measure that is well below anything seen in the past for this time of year. It is also one of the largest global negative sea-ice departures seen for any part of the record for any time of year — even when compared to the extreme period of Arctic sea ice loss during September of 2012.
Halloween Greenland Melt?

In addition to producing heatwaves, new temperature records, and ever more extreme sea ice melt, the odd Halloween warmth appears to also be generating flashes of surface melt over parts of northeastern Greenland. There, over the past few days, temperatures have approached or even exceeded the freezing point as warm winds have blown in from the heating Greenland Strait.
(A warm front crosses over northeastern Greenland on October 27, 2016. The associated warm winds blowing off the heating waters of the Greenland Strait produced near or above freezing temperatures for isolated parts of this section of Greenland. This abnormal warmth appears to have tripped NSIDC’s melt sensor, producing a possible odd late-season melt event for sections of this frozen island. Image source: Earth Nullschool.)

This heat has been enough to trip NSIDC’s Greenland melt indicators for the region of the Zachariæ Isstrøm glacier. These indicators, over the past couple of days, have shown relatively extensive melt in this sector of Greenland. During summer 2016, northeastern Greenland was one of the regions that saw strongest indications of surface melt. Typically isolated by sea ice from warm ocean breezes, northeast Greenland does not usually see such long-lasting periods of surface melt. This is especially true for late October as melt during this time for any portion of the Greenland Ice Sheet is practically unheard of. However, as warm ocean water has advanced further and further north, this region has become more vulnerable to invasions of warm air. And it appears that the melt-forcing effect of this ocean warming for nearby Greenland glaciers may well be extending into all.

Though unconfirmed by NSIDC, these periods of possible melt have occurred coincident with temperature departures in the range of 10-20 degrees C above average. However, since near or above freezing temperatures have mostly been isolated to the very far northeastern sections of Zachariæ Isstrøm near the coast, it’s likely that any potential and brief periods of melt were located in a more limited band than what has shown up on the NSIDC melt maps for October 27, 28, and 29. That said, as noted above, any surface melt over glaicers in Greenland for this time of year would be very odd and concerning — no matter how isolated.

Nasty Global Warming Tricks for Halloween

Halloween heatwaves, record-low sea ice extents and possible periods of fall Greenland melt are all indicators that human-forced climate change is starting to generate more and more obvious effects. Though the most extreme impacts are hitting remote regions like Greenland, the Arctic and the Antarctic, the related abnormal warmth has filtered into the middle latitudes and is now affecting millions of people across the U.S. And what’s happening in the U.S. is linked to these related warming events on a global scale.
So happy Halloween, everyone. Enjoy the holiday. But remember that if it’s oddly warm where you are, it’s not just a freak warm weather treat, but one of the many and worsening tricks conjured up by global climate change.
Links:

Hat tip to Colorado Bob
Hat tip to DT Lange
Hat tip to June


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