Arctic reaches its highest

Posted by Alexander Grobler on

While the Arctic reaches its highest at about this time every year, the Antarctic reaches its lowest extent for the year. The newest satellite data, released Wednesday, confirms that there is less sea ice worldwide than at any given time in the whole 38-year satellite record.

The NSIDC does not generally release data for both poles simultaneously, but has done so this time because of what scientists have dubbed an "especial" year in 2017.

Many of last year's extreme states have continued into 2017, the report noted.

Arctic Low

With just 14.42m square kilometers on March 7, this year's winter maximum in the Arctic ranks as the smallest in the satellite record, for the third year in a row.

Record low sea ice extent in February continued a sequence of records on the winter months, from October through February. A "heatwave" in mid-November caused some areas of the Arctic to be 15ºC warmer than usual, for instance.
Carbon Brief

The Arctic winter maximum has been shrinking by about three percent per decade. The downfall is substantially quicker for the summer minimum in September. Recent research shows up to two-thirds of the drop is a primary consequence of human activity.

Ice lost in the Arctic can have impacts considerably further afield, as a new WMO report clarified:

"Scientific research suggests that changes in the Arctic and melting sea ice is leading to some shift in wider oceanic and atmospheric circulation patterns. This is affecting weather in other areas of the world due to waves in the jet stream—the quick-moving band of air which helps regulate temperatures."

As we enter 2017's summer melt season, Arctic sea ice appears vulnerable. That is especially so, given that the latest sea ice thickness observations from the CryoSat 2 satellite show very thin ice in a number of regions, said a PhD student studying sea ice in the University of California, Zack Labe. Having said that, it's too soon to tell if we'll visit a record low minimum come he told Carbon Summary:

"Weather has a large role in the summertime melt season, so conjectures are challenging as to whether 2017 will be a brand new record minimum."
Greenland

The continent of Greenland has been experiencing unusual weather this winter, too while the behavior of Arctic sea ice will bring the biggest headlines.

Despite some periods of extreme cold, this winter has been warmer than average, according to Polar Portal, a site run by Danish researchers. A sequence of significant thunderstorms since October dumped more snow than normal on the southern and eastern areas of ice sheet, the scientists explained:

But while some claim this extra snowfall over winter means Greenland ice is at "record high" levels, this blows off a much larger part of the picture. Icebergs "calving" off the ice sheet and into the ocean account for much bigger decreases, described Dr. Ruth Mottram, a researcher at the Danish Meteorological Institute. Carbon Brief was told by her:

"Over the last decade, Greenland has lost around 200-300bn tonnes (gigatonnes, Gt) of ice each year; the additional snowfall we estimate from our models is about 150Gt. So it is not at all balancing what is lost by melting and calving in an average year."

The summer months—June, July and August —are the most essential for the ice sheet, so it's important to not read too much into significant snowfall over the winter season, Mottram added.

"Exceptional Year" in the Antarctic

Meanwhile, for the year, Antarctic sea ice continues to be experiencing its minimum extent at the opposite end of the earth.

Reached on March 3, the summer minimum caps off an unusually vigorous melt season, with new records.
Carbon Brief

How does 2017 compare to previous years? Natural changes play a big role in Antarctic climate, causing swings to year. Dr. Mark Brandon, a polar oceanographer at the Open University, told Carbon Summary:

"Only a couple of years ago the Antarctic sea ice extent was breaking records as being comparatively high, but this year it's shown record-breaking lows for a number of months."

The Antarctic's "exceptional year" in 2017 could even be a hangover from your powerful El Niño the world recently experienced, said Brandon:

This switch made the ice "more mobile and likely led to the relatively early Antarctic spring," clarified Brandon.
Having passed the summer minimum, sea ice has started growing again. But scientists will be keeping a detailed watch in coming months to view the way the ice fares within the winter freeze up season, described Prof. John Turner, a climatologist at the British Antarctic Survey. Carbon Summary was told by him:

"The rate of restoration after March 1 continues to be a little slow, although not too far off that which we see usually. It is just that the amount of ice is about 400,000 square kilometers less than the preceding minimum."

Such low ice cover at this time of year is unusual for recent times. Satellites have, in reality, measured a little increase in Antarctic sea ice over the past 20 years approximately, despite growing global temperature.

Quite a few variables might be behind this somewhat counterintuitive tendency, said Dr. Jonathan Day, an expert in sea-ice prediction at the University of Reading. He told Carbon Summary:

Evidence also implies an alteration in winds driven with an all-natural cycle in the tropical Pacific Ocean could possibly be behind recent Antarctic sea ice growth, said Day. Prof. Jerry Meehl, a scientist from the National Center for Atmospheric Research and lead author on that research, told Carbon Brief:

"The link in the tropical Pacific to the Antarctic involves a chain reaction of linked physical processes that ends up together with the winds around Antarctica affecting sea ice extent."

If natural variability has been masking the signal of human-caused climate change within the satellite interval in the Antarctic, this pattern will reverse at some stage. The truth is, it might have, said Meehl. He told Carbon Brief there is signs the Pacific cycle "switched" in 2015, which could mean we're finding the start of a falling trend in Antarctic sea ice.

But the message from scientists is that while this year, Antarctic sea ice is apparently bucking the trend, they need more than an individual year before they could tell if a long-term change is afoot.

Conclusion

Overall, it has been an exceptional year for the planet 's ice cover. While Antarctic sea ice has thrown up a number of intriguing questions for polar scientists, the consistent downward trend that characterizes the last three decades is continued by record low levels in the Arctic for this time of year.

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