JAXA ANTARCTIC Sea Ice Extent : 11,108,677 km2(June 6, 2019))Extent gains more above than below average in the last week.
2019 remains lowest in the satellite record for the 56th day this year, extent now 341 k below 2017.
- Extent gain on this day 121k, 2 k less than the average gain of 123 k on this day.
- Extent gain from minimum is 8.684 million km2, 1.068 million km2 (11%) less than the average of 9.752 million km2 by this day,
- 60.8% of average extent gain done, with 102 days to average date of maximum (16 Sept),
The Perils of ProjectionsRemaining average freeze of last 10 years gives a max of 17.39 million km2, 0.67 million km2 less than 2017 (the record low maximum year).
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I will only be posting occasional updates from now on unless something of note occurs, e.g. a series of posts on Global Sea Ice Extent from an individual querying the significance of loss of global sea ice, which was really about Antarctica.
So here is a reprise of the story of Antarctic sea ice in the satellite record that I have gleaned mainly from the ASIF and links provided by it.
From 1979 to to about 2010 the general trend of Antarctic Ice was to increase very very slowly - a glacial pace indeed.
Then
until the maximum maximum of 2014 and maximum minimum of 2013 the sea ice seemed to be increasing faster. The minimum grew at an even faster pace in percentage terms than the max.
WHY?
Scientists, including Hansen noted that the GRACE project showed that Antarctic Mass Loss (due to ice sheet loss) was increasing at an ever increasing rate. The result - a growing flood in the Southern summer of very cold FRESH water spreading out over the surrounding Southern Ocean, sitting as a layer on top of warmer but denser salt water. The freezing point of freshwater is higher than of salt water - hence sea ice growing.
BUTFrom 2014 to 2018 the sea ice maximum has dropped by 10%.
From 2013 to 2018 the sea ice minimum has dropped by 40%.
It is possible that in 2019 the maximum will drop by another 4 %
What's going on?The paper quoted below talks about 2016 and 2017. The change happened earlier and seems to be still happening. So since our knowledge of what's going on in Antarctica and why is inversely proportional to the size of the place under examination, the answer that belongs to me is a resounding - don't know.
We do know the air is heating,
We do know the oceans are heating,
We do know the Antarctic Ice Sheet , glaciers and ice shelves are melting.
And the area covered by sea ice is shrinking.
And that is definitely, absolutely all I'm going to say about that.
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https://www.nature.com/articles/s41467-018-07865-9Discussion
The evidence indicates that the rapid decrease in Antarctic sea ice
extent in late 2016 and the significant changes in the upper
Southern Ocean were likely caused by three factors. First, record
SST, precipitation, and convective heating anomalies in the
eastern tropical Indian and far-western Pacific Oceans produced
an anomalous Rossby wave response in the mid- and high
southern latitudes in SON 2016. The consequent teleconnection
pattern around Antarctica was characterized by a record negative
phase of the SAM, and a preponderance of warm, moist southward
surface winds that drove sea ice southwards and produced
decreased sea ice extent. Second, the anomalous surface winds
associated with this teleconnection pattern were also associated
with positive wind stress curl anomalies, southward Ekman
transport, and warmer surface water transported southward.
Third, a decadal timescale trend of negative wind stress curl
anomalies over the 2000s, associated with the positive trend of the
SAM and the negative phase of the IPO, moved warmer subsurface
water in the Southern Ocean upward in the column (part
of the so-called two-timescale response22–24). Then in late 2016,
the negative SAM contributed to producing anomalously warm
SSTs such that the entire upper 600m (over many areas of the
Southern Ocean) then was characterized by positive temperature
anomalies. These warmer ocean temperatures, combined with
the direct effects of surface wind forcing on the sea ice, produced
the rapid decrease of Antarctic sea ice extent. These conditions
were maintained through 2017, with reduced sea ice extent
compared to the average of the 2000s through JJA 2018.