A 40-y record reveals gradual Antarctic sea ice increases followed by decreases at rates far exceeding the rates seen in the Arctic
Claire L. Parkinson
PNAS first published July 1, 2019 https://doi.org/10.1073/pnas.1906556116
Contributed by Claire L. Parkinson, May 24, 2019 (sent for review April 16, 2019; reviewed by Will Hobbs and Douglas G. Martinson)
Significance
A newly completed 40-y record of satellite observations is used to quantify changes in Antarctic sea ice coverage since the late 1970s. Sea ice spreads over vast areas and has major impacts on the rest of the climate system, reflecting solar radiation and restricting ocean/atmosphere exchanges. The satellite record reveals that a gradual, decades-long overall increase in Antarctic sea ice extents reversed in 2014, with subsequent rates of decrease in 2014–2017 far exceeding the more widely publicized decay rates experienced in the Arctic. The rapid decreases reduced the Antarctic sea ice extents to their lowest values in the 40-y record, both on a yearly average basis (record low in 2017) and on a monthly basis (record low in February 2017).
Abstract
Following over 3 decades of gradual but uneven increases in sea ice coverage, the yearly average Antarctic sea ice extents reached a record high of 12.8 × 106 km2 in 2014, followed by a decline so precipitous that they reached their lowest value in the 40-y 1979–2018 satellite multichannel passive-microwave record, 10.7 × 106 km2, in 2017. In contrast, it took the Arctic sea ice cover a full 3 decades to register a loss that great in yearly average ice extents. Still, when considering the 40-y record as a whole, the Antarctic sea ice continues to have a positive overall trend in yearly average ice extents, although at 11,300 ± 5,300 km2⋅y−1, this trend is only 50% of the trend for 1979–2014, before the precipitous decline. Four of the 5 sectors into which the Antarctic sea ice cover is divided all also have 40-y positive trends that are well reduced from their 2014–2017 values. The one anomalous sector in this regard, the Bellingshausen/Amundsen Seas, has a 40-y negative trend, with the yearly average ice extents decreasing overall in the first 3 decades, reaching a minimum in 2007, and exhibiting an overall upward trend since 2007 (i.e., reflecting a reversal in the opposite direction from the other 4 sectors and the Antarctic sea ice cover as a whole).
Since the late 1990s, it has been clear that the Arctic sea ice cover has been decreasing in extent over the course of the multichannel passive-microwave satellite record begun in late 1978 (1⇓–3). The decreases have accelerated since the 1990s and have been part of a consistent suite of changes in the Arctic, including rising atmospheric temperatures, melting land ice, thawing permafrost, longer growing seasons, increased coastal erosion, and warming oceans (4, 5). Overall, it has been a consistent picture solidly in line with the expectations of the warming climate predicted from increases in greenhouse gases. In particular, modeled sea ice predictions showed marked Arctic sea ice decreases, and the actual decreases even exceeded what the models predicted (6).
The Antarctic situation has been quite different, with sea ice extent increasing overall for much of the period since 1978 (7⇓⇓⇓–11). These increases have been far more puzzling than the Arctic sea ice decreases and have led to a variety of suggested explanations, from ties to the ozone hole (12, 13; rejected in refs. 14, 15); to ties to the El Niño–Southern Oscillation (ENSO) (16), the Interdecadal Pacific Oscillation (17), and/or the Amundsen Sea Low (10, 13, 17); to ties to basal meltwater from the ice shelves (18; rejected in ref. 19). None of these has yet yielded a consensus view of why the long-term Antarctic sea ice increases occurred.
In the meantime, while the unexpected, decades-long overall increases in Antarctic sea ice extent are still being puzzled out, the sea ice extent has taken a dramatic turn from relatively gradual increases to rapid decreases. On a yearly average basis, the peak sea ice extent since 1978 came in 2014. Since then, the decreases have been so great that the yearly averages for 2017 and 2018 are the lowest in the entire 1979–2018 record, essentially wiping out the 35 y of overall ice extent increases in just a few years. This dramatic reversal in the changes occurring in the Antarctic sea ice will provide valuable further information to test earlier suggested explanations of the long-term Antarctic sea ice increases. We now have a 40-y multichannel passive-microwave satellite record of the Antarctic sea ice cover, all of which resides in the Southern Ocean. The purpose of this paper is to present that record both for the Southern Ocean as a whole (labeled “Southern Hemisphere” in the figures, to emphasize the inclusion of the entire hemispheric sea ice cover) and for the breakdown of the Southern Ocean into the 5 sectors identified in Fig. 1.
Full paper here. Not paywalled.
Doesn’t Antarctic sea-ice normally go to near-zero every summer?
No.
An ascending sort of the Antarctic sea ice (extent) data provided in
ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/south/monthly/data/
looks like this (absolute values in Mkm²):
2017 2: 2.29
2018 2: 2.29
1993 2: 2.48
1997 2: 2.49
2011 2: 2.52
2006 2: 2.65
2019 2: 2.66
1984 2: 2.68
2017 3: 2.70
2016 2: 2.79
1980 2: 2.82
1985 2: 2.84
1992 2: 2.84
1981 2: 2.87
1988 2: 2.89
2007 2: 2.90
2000 2: 2.91
2002 2: 2.96
1999 2: 2.97
2005 2: 2.97
1989 2: 2.98
1996 2: 2.98
1998 2: 2.99
2009 2: 2.99
1990 2: 3.04
For the pack ice the lowest value is a little bit less than for the extent but it is not close to zero either.
You would think that after a couple of decades of colder than average temperatures, the ice on the poles would be higher than average…
So we use that ice level/ice extent as the new normal…
And now we face a global crisis because we discovered that warmer temperatures cause ice to melt.
If only we had a way to know the ice level/ice extent before 1979…
We have. Take a look at the first IPCC report. It has ice data from 1973. But the first six years have since evaporated.
Or rather, what happened in 1979 is that the definition of “ice free” was changed from <10% ice, to <15% ice, and since the ten percent definition has been used from time immemorial (a sailing vessel can penetrate about 10% ice, no more) this means that most data before 1979 are no longer compatible with younger data. Smart move.
As a matter of fact using early weather satellite data, declassified recce satellite images and air recce/ship data it would be possible to get quite good data back at least to the early sixties. As a matter of fact there was a project to get ice data from the early NIMBUS satellites (1964-71) several years ago. It was completed and the data are available, but have never been published….
https://nsidc.org/data/nimbus/data-sets.html
In the North Atlantic sector data go back much further:
http://www.climate-cryosphere.org/resources/historical-ice-chart-archive
CORONA, ARGON and LANYARD satellite imagery 1960-1975 is also freely available, but has never been analyzed:
https://gcmd.gsfc.nasa.gov/KeywordSearch/Metadata.do?Portal=amd&KeywordPath=&OrigMetadataNode=GCMD&EntryId=CORONA_SATELLITE_PHOTOS&MetadataView=Full&MetadataType=0&lbnode=mdlb4
One might almost think that climate scientists aren't really that interested in data older than 1979…..
The not-very-alarming drop is largely due to a decrease in the sea-ice maxima.
The Antarctic sea-ice minima have actually *increased* for three years running.
The Antarctic sea-ice maximum is pretty meaningless and a decrease in it is probably the result of storms or compression.
How much effect do those 125+ active geothermal vents under the West Antartic ice sheet have on overall ice amounts?
These little blips up and down in ice melt, will leave a signal unnoticeable in the ice core records as the top layers diffuse together in a mixed bag of faster and slower melt seasons. Nothing of significance to scientists a couple 10s of thousands years from now. But I guess it keeps our hands and brains busy for now.
ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/ice-cores.pdf
“But I guess it keeps our hands and brains busy for now.”
Brains, not so much. Fuel for worrywarts, much.
40 years of data results in only one datum point on the climate graph and therefore cannot be used for establishing any trend in climate terms.
Short term wobbles can be interesting; but when the conjectures all seem to revolve around the dreaded CO2 Meme, it gets very boring.
Does anyone else think that one slow rise and one dip are too little data to proclaim that the sky is falling?
read the article
Not the point, Mr. Mosher; its the misuse of minor CliSci “studies” by activists, dependent politicians and the MSM. Many (most?) WUWT responses reflect that concern.
So when do we start planting the vines? Does Griff know?
Maybe they should have included the recovered NIMBUS satellite data from the 60’s as well.
“The Antarctic really blew us away, in 1964 we found the largest sea ice ever recorded! Bigger than what we’re seeing today (2014) But just two years later in 1966 was the SMALLEST sea ice ever recorded! In 1969 was the EARLIEST sea extent maximum recorded!”
I’ll go out on a limb and say Antarctic sea ice fluctuates……a lot.
https://wattsupwiththat.com/2014/09/04/1960s-satellite-imagery-of-polar-ice-discovers-enormous-holes-in-the-sea-ice/
But … but … but didn’t climate change start in 1979? All the climate models are tuned for the 25-30 year period beginning then!
“But … but … but didn’t climate change start in 1979? All the climate models are tuned for the 25-30 year period beginning then!”
err no. factually, no.
You’re actually correct, Mr. Mosher; I fudged the start date forward by 4 years, taking poetic licence to reflect the satellite data 1979 start date.
Please note that the UN IPCC climate model historical output “spaghetti graphs” have results that are all over the place between the models, then neck down in the late ’70’s. Afterwards, they all balloon out again. This is evidence of late 20th Century model tuning since the different models have wildly differing ECSs.
The UN IPCC climate modelers themselves state they tune the models to get an ECS that “seems about right.” Hell, they can’t even get the major historical temperature trend deviations (up or down) right in their hindcasts. As much as they fiddle with past aerosols, etc., their models cannot provide fidelity with the past climate because they tune to the late 20th Century.
Thanks Gonzo!
More data to show the trolls what whinging fools they really are.
J Mac, they are not fools; they know exactly what they are doing and are reaping the benefits.
Alarmists enjoy these hang-wringing publications of polar ice doom. However, if the Antarctic ice didn’t regularly return to the sea, then all the water on the planet would wind up at the South Pole. We’d be living on a desert planet similar to Mars–where all the water is locked up at the poles.
There’s an interesting article I read in Science a few years ago (Holocene Deglaciation of Marie Byrd Land, West Antarctica. Science. 1/3/2003, Vol. 299 Issue 5603, p99-102). After you get past the usual AGW nonsense, the authors claim that the WAIS is also responding to heating events from thousands of years ago. In other words, the ice sheet has a long memory. You can’t just limit an ice sheet’s response to the current temperature–you must also take into consideration past climatic warming events.
Even if we totally stopped (so-called) AGW, the WAIS would still be responding to the Holocene Optimum (which it probably is anyway).
Jim
Stupid typos: hang-wringing should be hand-wringing.
Jim
Stupid typos: hang-wringing should be hand-wringing.
Another Freudian slip:
Donergott thor hangs in the world ash, the dangerous pouring acid rains through the foliage destroy 1 eye.
The condition that thor could learn to read the runes – needed that he could lead “his” people through bad times!
The paper, apart from the obligatory homage to anthropogenic warming, is actually a valuable presentation of quality data. Some of her conclusions seem a bit forced, but when you work for NASA, you need to conform to the house rules or bad things might happen to you.
For me, the telling points are made by figure 2, which is at:
There are two things that make the “precipitous decline” stand out. The yearly averages fell from about 13.9 to about 10.8 wadhams between 2014 and 2017. Alternatively, it fell from about 0.9 wadhams above the trend line shown in the graph, to about 1.1 wadhams below the trend line. If you ignore the “precipitous increase” from 2011 to 2014, then the decline becomes much less precipitous. Note: 1 wadham = 1 million km² as a tribute to the inimitable Peter “ice-free Arctic by 2013” Wadhams. I didn’t invent the term but it started appearing om WUWT a few years ago.
And if you look at figure 3, which shows the ice on the Weddell Sea (one of the five sectors of the Southern Ocean), here
You see a decline from 2014 to 2017 of about 0.9 wadhams, and you have explained almost the whole “precipitous decline” by a decline in the Weddell sea ice, with the other 4 sectors not really doing much of anything. And the decline in the Weddell Sea ice from 2014 to 2017 isn’t that much different from the decline of 0.7 wadhams from1980 to 1982, or the increase of 0.9 wadhams from 1999 to 2003.
It’s only arm-waving, but I think I’ve convinced myself that I’ve managed to “hide the decline”. Or rather, that the decline is not really distinct from being part of a randomly varying quantity.
Then again, the earth’s climate has been getting warmer for about 300 years, and there’s no reason to assume that all the secondary effects of warming, like modest reductions in sea ice, are going to change at a constant, monotonic rate. Precipitous short-term changes in either direction are to be expected.
Isn’t the time span for the “precipitous decline” too short to attribute to climate yet ? It’s what a five-year span?
Wouldn’t we need, say, another twenty-five years to see what the climatic trend would be ?
They didnt attribute it to climate
My disbelief of CAGW remains when there is so many diametrically opposed comments in one paper.
Here they are saying that the models have it right in the Arctic – ‘solidly in line with expectations’ – and, at the same time, ‘exceeded what the models predicted’. Were the expectations that they would be wrong and always worse that they thought?
Then, for Antarctica, there is no consensus from the theories and models so why believe they have it right for one pole and not the other?
The CAGW argument has to be consistent.
The CMIP3 models (used in the UN IPCC AR4) badly screwed up (overestimated) Arctic ice. In an attempt to better follow actual Arctic ice trends, they (arbitrarily) jiggered with the parameters for the CMIP5 models (AR5) such that the UN IPCC modelers actually made the representation of other climactic metrics worse.
Its like putting a girdle on a fat lady; things pop out at the oddest places.
Climate Change Confusion: What Are We to Think?
http://bit.ly/2Gn6dBn
Antarctica, on the other hand, where the ice cap sits on land, is the highest and coldest continent on Earth. It’s more than 5.4 million square miles in extent with an average altitude more than 8,000 feet, has 2,660 mountains (one over 16,000 feet), and is covered with ice averaging more than 6,000 feet in thickness.
As for those massive ice sheets extending over water? The glaciological record shows there have been many retreats of the West Antarctic ice sheet that left it more than 100,000 square miles smaller than it is today. And we also know that the Eastern ice sheet has been cooling for the past half century. And really, a concerned citizen might want to know, how could a slight warming of Earth (if that is true) change much on such a massive continent where the average annual temperature is minus 50 C, and where, in 2013, the coldest temperature ever recorded on Earth was minus 93 C?
Green magic CO2 is quite selective in its warming: first mainly the Arctic seas and decades later the Antarctic seas after 2014.
A real scientific con sensus case!
Doesn’t the melting of ice remove heat from a system?
please see
https://tambonthongchai.com/2019/07/02/antarctic-sea-ice-collapse-of-2019/
“Since the late 1990s, it has been clear that the Arctic sea ice cover has been decreasing in extent over the course of the multichannel passive-microwave satellite record begun in late 1978”
Not true, JAXA, DMI, SII and MASIE all show that Arctic ice has not reduced since 2007.
Growing in leaps and bounds, we’re on the cusp of some alarming neo-quasi-glaciation.
http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger/ice_volume/BPIOMASIceVolumeAprSepCurrent.png
Loydo
Thanks for the humor we all need!
But… the PIOMAS people undoubtedly have competition, namely from DMI.
Please download the data behind the graph you show
http://psc.apl.washington.edu/wordpress/wp-content/uploads/schweiger/ice_volume/PIOMAS.2sst.monthly.Current.v2.1.txt
and DMI’s Arctic ice volume data
http://ocean.dmi.dk/arctic/icethickness/txt/IceVol.txt
which you easily can transform in a monthly time series.
You obtain the following comparison based on absolute values (starting with DMI in Jan 2003)
https://drive.google.com/file/d/1H7KXADacA6sXEAZi_T_4njZyJQkAmsUT/view
An anomaly-based comparison based on a reference period 2003-2017 yields the same impression
https://drive.google.com/file/d/1t8urXkZ8Fkp8z8weywAf84VNjdFhqhu3/view
You see that PIOMAS’ evaluation is quite a lot below DMI’s. A typical example: Jan-Jun 2019, PIOMAS vs. DMI
2019 1 16.91 19.45
2019 2 19.78 21.67
2019 3 21.79 23.15
2019 4 22.37 23.66
2019 5 21.01 22.82
2019 6 15.91 18.22
Who is right? We all here don’t know. All I know is that unsound skeptics will say DMI is right, and that unsound alarmists will say PIOMAS is. Neither helps.
Who cares-
https://notrickszone.com/2018/10/18/new-science-arctic-and-antarctic-sea-ice-more-extensive-today-than-nearly-all-of-the-last-10000-years/
Two statistical points.
(1) This is a very short record.
(2) THIS IS TIME SERIES DATA, GOSH DARN IT! It makes *no* sense to do a linear regression on it!
There are well established ways to analyse time series. This isn’t even close. Don’t they have
anyone at the Cryospheric Sciences Laboratory who has a glimmer of a clue about undergraduate
statistics? How did peer review fail so egregiously?
Look, this is an interesting data set. But this is quite literally a sophomoric way to analyse it.
I used to supervise MSc and PhD students, and if one of my students had shown me a paper
draft like this I would have spent *weeks* helping them rewrite it.
My concern in this case has nothing to do with climate. This is a publication in PNAS by an
elected member of the NAS, dealing with important data in a very poor way, and two
*named* reviewers didn’t blink an eyelid at it. I expect they are all very nice hardworking
people, but shouldn’t *someone* with a statistician’s mindset look at a paper like this?
I have revised this several times, and I try to use polite and measured language, but you should
imagine me screaming and banging my head against the wall. When I read page 2, left
column, last paragraph, I wanted to be SICK.
The paper has given us no reason to believe that any of the apparent patterns in the data is
real or that anything unusual would be happening if they were.