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Antarctic Sea Ice lowest in 40 years, but no one knows why — “back to drawing board”

Posted By Jo Nova On July 5, 2019 @ 7:19 pm In Global Warming,Marine,Media-matters | Comments Disabled

Put it in a history book: scientists are sounding like scientists — admitting they don’t understand

Antarctic Sea Ice set records in 2014, but then in 2016 it rapidly declined and hasn’t recovered, indeed right now as the southern winter peaks, it’s at a record low. The long term trend is still rising, but its now only half the rate it was in 2014. On this blog, Mike Jonas recently demonstrated that the Southern Ocean had cooled, not warmed as all the models predicted. But what matters here is that sea ice covers 7% of the world and we don’t know what caused it.

What is also a record is that most scientists and journalists are showing real restraint and are not blaming this as a climate change event.

Even, bowl-me-over, New Scientist, is showing admirable restraint: Antarctic sea ice is declining dramatically and we don’t know why. This is the first time since starting this blog ten years ago that I have been able to say that. Congrats Adam Vaughan.

Decades of expanding sea ice in Antarctica have been wiped out by three years of sudden and dramatic declines, leaving scientist puzzled as to why the region has flipped so abruptly. However, researchers cautioned against pinning the changes on climate change and said it was too early to say if the shrinking is the start of a long-term trend or a blip.

The decline may just be natural variability, driven by shift in wind patterns which influence the extent of Antarctic sea ice, says Mark Serreze, director of the US National Snow and Ice Data Center. “To argue that this recent dip is evidence of the start of a longer term decline driven by greenhouse warming is premature.”       — New Scientist.

On average across the seasons there is about 13 million square kilometers of sea ice around Antarctica, so even though this is a record low, it’s still only 10% below normal. Right now, because its winter, there is 14 million square km of sea ice , but at this time of year normally there would be 15 million km2.

Antarctic Sea Ice, Graph, June, 2019.

Antarctic Sea Ice, Graph, June, 2019. Source: NSIDC

 

The water around Antarctica is no warmer than normal for this time of year:

You might think a warm sea current could be to blame, but it’s not that simple. The black area around the ice below shows the sea surface temperature today has a 0.0C “anomaly”. In other words, spot on average. (Though this is not a trend graph, just a daily situation graph, which can change quickly).

The Southern Ocean long term trends are what matters. This above, is a pretty picture, symbolic, but just a snapshot.

 Scientists admit they have to go back to the drawing board:

Maddie Stone, Gizmodo — January 2019:

“Notably, the November to December 2016 period was considered an extreme excursion of Antarctic sea ice at the time,” the NSDIC wrote.

In short, scientists pinned the last sea ice nosedive on natural variability. But it’s currently unclear what’s behind this year’s ice crash. Notably, University of Washington sea ice researcher Cecilia Bitz told Earther that the Southern Annular Mode is not strongly negative at the moment. Nor are we still nursing the hangover of a monster El Niño, as we were at the end of 2016.

“I think we have to go back to the drawing board a little bit,” Bitz told Earther.

Bitz was reluctant to speculate as to whether the near back-to-back sea ice slumps are part of a new trend associated with climate change. While parts of Antarctica are definitely feeling the heat, until recently, Antarctic sea ice was growing slightly, reaching a record high in 2014. That doesn’t negate the warming trend, it simply speaks to the complexity of sea ice behaviour in an environment impacted by both ocean currents and a giant continent.

Son Ngheim, a senior research scientist at NASA’s Jet Propulsion Laboratory, told Earther that everything from winds driven by Antarctic continental topography to currents controlled by the shape of the Southern Ocean’s seafloor influences Antarctic sea ice. Bitz pointed to ice melting on the edges of the continent as a factor that could, paradoxically, help new sea ice form by preventing warmer deep waters from rising to the surface. Snowfall might also influence year to year variability in ice, according to NASA.

“Another point of low sea ice extent in the Antarctic this year still cannot be considered as a climatic trend,” Ngheim wrote Earther in an email, noting that spates of record lows occurred in the early part of the satellite record, as well.

Mark Kaufman, Mashable, reports that the Antarctic sea ice was volatile in the 1960s

Meier has studied some of the earliest satellite imagery of Antarctica, from the 1960s. Though the old pictures are of lower quality and incomplete compared to modern satellite records, it does paint a picture of a highly variable Antarctic — similar to what Parkinson has recently observed. There were almost certainly giant swings in the Antarctic sea ice some 60 years ago, with a big drop comparable to that occurring in recent years, he noted.

Again, reported with admirable caution:

One thing, however, is more certain. In stark contrast to the Arctic, it’s much too soon to say whether global warming is at fault. “Anyone who speculates conclusively that the new downward trends are related to climate change are far overstating the understanding we have,” noted Campbell.

But look who’s still printing wild hyperbole — USA Today and The Guardian

No matter how little we know, it’s still climate change according to Damien Carrington:

‘Precipitous’ fall in Antarctic sea ice since 2014 revealed:

 Plunge is far faster than in Arctic and may lead to more global heating, say scientists

The Guardian: The plunge in the average annual extent means Antarctica lost as much sea ice in four years as the Arctic lost in 34 years. The cause of the sharp Antarctic losses is as yet unknown and only time will tell whether the ice recovers or continues to decline.

But researchers said it showed ice could disappear much more rapidly than previously thought.

Which is another way of saying “scientists got it wrong”. Sea Ice showed scientists it could grow much faster than previously thought too. Did The Guardian mention that?

Count the excuses — something just flipped and researchers don’t know what it was:

“The Arctic has become a poster child for global warming,” Parkinson said, but the recent sea ice falls in Antarctica have been far worse. She has tracked Antarctic sea ice for more than 40 years. “All of us scientists were thinking eventually global warming is going to catch up in the Antarctic,” she said.

Kaitlin Naughten, a sea ice expert at the British Antarctic Survey, said: “Westerly winds which surround the continent mean that Antarctic sea ice doesn’t respond directly to global warming averaged over the whole planet.”

“Climate change is affecting the winds, but so is the ozone hole and short-term cycles like El Niño. The sea ice is also affected by meltwater running off from the Antarctic ice sheet,” she said. “Until 2014, the total effect of all these factors was for Antarctic sea ice to expand. But in 2014, something flipped, and the sea ice has since declined dramatically. Now scientists are trying to figure out exactly why this happened.”

The only real horror here, is how little we understand the climate.

USA Today mentions man-made climate change, and quotes Mark Serreze, director of the National Snow and Ice Data Center doing a bit of emotional advertising for the cause. He called the plummeting ice levels “a white-knuckle ride.” ( Jo wonders how much should we panic if Antarctic Sea ice is close to where it was in 1981? Shock, horror. “The Eighties”? )


Here’s the usual graph of  Antarctic Sea Ice Extent:

Antarctic Sea Ice Extent, Map, June 2019.

Antarctic Sea Ice Extent, Map, June 2019.

https://nsidc.org/data/seaice_index/images/daily_images/S_iqr_timeseries.png

The Map, for completeness and perspective.

Antarctic Sea Ice Anomaly. Graph.

Antarctic Sea Ice Anomaly. Graph.

 

Climate4U reminds us that sea ice covers 7% of Earth, and Antarctic sea ice almost disappears each summer because it stretches so far north of the pole:

Sea ice occupies about 7% of the surface area of planet Earth. The sea ice thickness, its spatial extent, and the fraction of open water within the ice pack can vary rapidly and profoundly in response to weather and climate. Sea ice typically covers about 14 to 16 million square kilometres in late winter in the Arctic and 17 to 20 million square kilometres in the Southern Ocean around the Antarctic. The seasonal decrease is much larger around the Antarctic, with only about three to four million square kilometres remaining at summer’s end, compared to approximately seven to nine million square kilometres in the Arctic. The main reason for this difference is that the Arctic Ocean is centred on the Pole, while the Southern Ocean is not.

Finally something that melted is  due to natural climate variability

From January this year:

https://phys.org/news/2019-01-antarctica-sea-ice-climate.html

 Taken together, the evidence we present supports the idea that the rapid Antarctic sea ice decline in late 2016 was largely due to natural climate variability.

Since then, sea ice has remained mostly well below average in association with warmer upper ocean temperatures around Antarctica.

While scientists are just guessing — is it winds?

We argue these are the product of stronger than normal westerly winds in the previous 15 or so years around Antarctica, driven again from the tropics. These stronger westerlies induced a response in the ocean, with warmer subsurface water moving towards the surface over time.

Could warm tropical waters melt Antarctic sea ice? C’mon guys…

The combination of record tropical  and weakened westerly winds in 2016 warmed the entire upper 600m of water in most regions of the Southern Ocean around Antarctica. These warmer ocean temperatures have maintained the reduced extent of sea ice.

REFERENCE:

Clair, L. Parkinson (2019) A 40-y record reveals gradual Antarctic sea ice increases followed by decreases at rates far exceeding the rates seen in the Arctic, PNASDOI: 10.1073/pnas.1906556116

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