Tuesday, 8 May 2018

Major heat wave in the Arctic

Even when he's not talking about electric cars I no longer see Robertscribbler as a totally honest player

Arctic Ocean Deep in the Grips of May Temperature Spike; Beastly Summer Melt Season on the Way?

The Arctic Ocean as it appeared from space on May 6, 2018. Image source: NASA Worldview.
7 May, 2018

The Arctic sea ice is presently at its second lowest extent ever recorded in most of the major monitors. However, May is shaping up to be far, far warmer than normal for the Arctic Ocean region. If such high temperatures over this typically-frozen part of our world continue for much longer than a couple of weeks at this key time of year, precipitous summer melt is sure to follow.

During recent years there has been much speculation about when the Arctic Ocean will start to experience ice-free summers as fossil fuel related industries pump higher and higher volumes of greenhouse gasses into the atmosphere. In the early-to-mid 2000s, scientific consensus was that melt would tend to be more gradual and ice-free summers would hold off until the final decades of the 21st Century when the world was around 3-4 C warmer than 19th Century averages.
But the Earth System is far more sensitive to temperature increases than the early forecasts expected. Major Arctic sea ice losses surprised the world during September of 2007 and subsequently in the same month of 2012. Now, it is obvious that a pattern of far more rapid sea ice melt has taken hold. And the scientific consensus appears to have settled on a more likely and much nearer date around the early 2030s — when the world will have warmed by about 1.6 degrees Celsius.

However, when it comes to sea ice, nothing is certain at this time. Any single Arctic year in which temperatures spike — particularly during normal melt season — could result in the losses that we once expected to occur much later in time.

There are many factors that will ultimately determine when a summer ice free state occurs. Warm winters are a major one. And the past two years (2017 and 2018) have seen Arctic winters in which temperatures hit some ridiculous high extremes. But another major factor is the set-up to Arctic summer that takes place during the window months of May and June.

Neven, one of our best Arctic Sea Ice watchers (you can check his blog out here), notes:
May and June are very important for the rest of the melting season. Not only do we now see these warm air intrusions, but high pressure maintains its presence over parts of the Arctic as well (which means relatively cloudless skies -> insolation -> melt onset and melt pond formation -> preconditioning of the ice pack -> melting momentum that gets expressed during July and August, regardless of the weather)… We have to wait and see what happens, step by step, but this isn’t a good start for the ice.
If May and June are unusually warm, particularly over the Arctic Ocean, then the sea ice — which is already greatly weakened — is bound to face an extended period of above-freezing temperatures. If such a period stretches for 5 months from May through September rather than the typical 4 months (June to September), then we are more likely to see the Arctic Ocean briefly flip into an ice-free or near ice-free state for the first time in human history.
(The coming week is expected to feature between 1 and 10 C above average temperatures for locations across the Arctic Ocean. These are very strong warm departures during May. Last week saw similar extreme warm departures. And we are already starting to see sea ice losses pile up. Image source: Global and Regional Climate Anomalies.)

This year, May is shaping up to be much, much warmer than normal for the High Arctic. Already, a large May temperature spike has occurred (see right image below). A temperature spike which is predicted to continue for at least the next ten days.

Not to put too fine a point on it, but this severe warming trend might end up presenting a bit of a problem. The extended period of melt mentioned above may begin in force — setting off a chain of feedbacks that could tip the Arctic Ocean into a far less frozen or even an ice-free state (under absolute worst case scenarios) this year.
To be clear, this is not a forecast that such a condition is bound to occur during 2018. It is just an analysis of underlying trends and a statement that risks are higher if such trends as we now observe continue. Late May could flip to a cooler than normal regime. June could be cooler and cloudier than normal (as happened during 2016 and 2017). And if that happens again, we may be spared.
(Average Arctic temperatures for 2017 [left] and 2018 [right]. The red line depicts the yearly temperature trend. The green line depicts the Arctic climatological average for 1958-2002 [which was already warmer than normal]. Note the big temperature spike in the right hand graph. That’s where we are now. Image source: DMI. For further reference, see Zack Labe‘s composite temperature analysis for the 80 North region.)

However, we are already on a much higher ramp for spring temperatures in the northern polar region than during 2017. And though 2016 saw a slightly warmer than normal spring near the pole, the May 2018 spike already far exceeds anything we saw at that time. So much, in fact, that present temperatures for May 6 are comparable to those typically seen during early June from the 80 degree N Latitude line to the Pole.

This higher ramp and related record warmth is already accelerating melt. Sea ice losses over recent days have greatly picked up and we are getting closer to record low daily ranges. If melt accelerates to a point, the greatly expanded darker ocean surfaces will draw in more heat from the sun’s rays during June — potentially overcoming the impact of the increased early summer cloudiness we have seen during recent years. Such a scenario, if it continues to develop, would be a nightmare from the climate change perspective.

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