It’s winter in the Antarctic. Time for another seasonal revival of the “Antarctic Ice is Growing” Crock.
Guy Williams is Co-leader of the ‘Sea Ice Processes and Change’ project within the ‘Oceans and Cryosphere’ research program of the Antarctic Climate and Ecosytem Cooperative Research Centre at the University of Tasmania.
Guy Williams in The Conversation:
This year could well see a new record set for the extent of Antarctic sea ice – hot on the heels of last year’s record, which in turn is part of a puzzling 33-year trend in increasing sea ice around Antarctica.
Unsurprisingly, these records have provided fodder for those wishing to cast doubt on climate science or to resist action on climate change. The Intergovernmental Panel on Climate Change (IPCC) itself states that while hypotheses exist for Antarctic sea ice trends, they are “incomplete and competing” (see page 909 here).
But far from waving the white flag, or falling on their ice corers, Antarctic sea ice researchers are relishing this grand puzzle of the Southern Ocean.
In terms of natural experiments, they don’t come much bigger or more exciting than those unfolding across the Antarctic climate system right now. What’s more, the science is beginning to yield answers.
It’s currently autumn in the Southern Hemisphere — which means that Antarctic sea ice is once again marching north, responding to the cold, dark polar winter. It’s one of Earth’s greatest seasonal changes.
Sea ice is the ephemeral lovechild born from an ocean coupled with a cold atmosphere. It is very sensitive to the complex interplay of thermodynamic (freezing and melting) and mechanical (compacting, ridging, rafting, breaking) processes driven by both parents.
As such, sea ice is a canary in the coalmine for changes to polar climate.
That much has certainly been obvious in the Arctic. The dramatic decline of Arctic sea ice since 1981 is now firmly in the public consciousness as proof that global warming is real, and that it is a serious and pressing issue. The Arctic canary is unwell, to say the least.
However at the other end of the planet, the Antarctic canary seems to be singing away happily, as the total extent has grown, albeit weakly, over the same period. The past two years have each been record-breakers, and 2014 looks to be building the same way. You can track how it’s going here, which shows how much more sea ice there is relative to the 1981-2010 average.
Perhaps the most important fact about the (slight) increase in total Antarctic sea ice extent is that it masks major and contrasting regional changes. For example, there has been a strong decrease in sea ice duration in the Bellingshausen Sea, while the duration has increased in the western Ross Sea. Such curiosities have led sea ice scientists to investigate several possible mechanisms, and explanations for these patterns are now starting to emerge.
The Amundsen Sea Low is a pattern of low atmospheric pressure in the Pacific part of the Southern Ocean, which drags warm air south and pushes cold air north. This southward flow of warm air meets Antarctica in the Bellingshausen Sea, explaining why ice in this area is now in decline.
Meanwhile, the cold air is being pushed north from the western Ross sea — where sea ice extent is increasing. So the Amundsen Sea Low can be used to explain at least two variations in Antarctic sea ice.
The Southern Annular Mode (SAM) (also called the Antarctic Oscillation) is a term that describes the north-south position of the westerly wind belt that encircles Antarctica in the Southern Ocean. These winds are known variously as the “roaring 40s”, “furious 50s”, and “screaming 60s” depending on their latitude, and when they meet sea ice they drive it northwards (away from Antarctica).
Like many other climate patterns (such as El Niño/La Niña), SAM has “positive” and “negative” phases. A positive SAM pushes the winds south to higher latitudes, meaning they encounter more sea ice, pushing more of it northwards and increasing the total ice extent.
The Amundsen Sea Low also strengthens with the Southern Annular Mode’s positive phase. The mode has been strongly positive over the past three decades, helping to explain the overall increase in Antarctic sea ice extent, as well as the regional variations.
Here’s the kicker: the strengthening of SAM over recent decades has been directly linked to human activity. Since the 1940s, ozone depletion and increasing greenhouse gases have caused the westerly winds to intensify and migrate south towards Antarctica. The net effect of this drives sea ice further north and increases its total extent.
There is still plenty of great work ahead to improve our understanding and modelling of Antarctica’s climate, but a basic message is emerging. Far from discounting climate change in the Southern Hemisphere, the apparent paradox of Antarctic sea ice is telling us that it is real and that we are contributing to it.
The Antarctic canary is alive, but its feathers are increasingly wind-ruffled.
There is some evidence that Antarctic sea ice mostly disappeared before 1980
http://tamino.wordpress.com/2010/10/16/history-of-arctic-and-antarctic-sea-ice-part-1/
a quote: “The data are clear: sea ice extent declined dramatically during the 20th century in BOTH hemispheres.” If Tamino is correct, Antarctic sea ice is currently less than half what it was prior to 1950. It is currently, in effect, increasing from ‘zero’, which is not hard to do for any system.
http://www.gocomics.com/calvinandhobbes/1987/07/23#.U7trGKhGgrx
Peter,
I am comparing this video with things that Jennifer Francis has said and I need you to help me understand this. The video says that the winds encircling Antarctica are faster now, and at the 5:40 mark it says this is partly because “with global warming the temperature difference between the equator and the poles is greater.” But in professor Francis’ video I thought she said that in the northern hemisphere the jet stream was slowing and that this was partly because with global warming the temperature difference between the equator and the poles was LESS (on account of the fact that the arctic is warming more rapidly than the rest of the world. Please help me understand this, what am I missing? Thanks
great question.
Remember – the antarctic is a very different place than the arctic. “polar opposites”, you might say.
The arctic is a very thin layer of ice on a deep ocean that is obviously above freezing temperatures. As that ice gets peeled away, the water is revealed and, for the first time, ambient temperatures are above freezing, in some cases much above freezing. So the differential with the temperate zone, for large areas, is decreasing.
The antarctic is the opposite case – a land-based block of ice larger than the continental US, 10x the size of Greenland, and a mile or two thick. Much of the surface is cold not just by geography, but by elevation, so there is almost no surface melt on Antarctica.(it is being eaten away below the water line, so to speak) It remains very high and very cold, even as the rest of the world warms – so scientists are saying that the difference in the southern hemisphere, between the southern ocean and the ice, is increasing – leading to stronger circumpolar winds in the south.
Thanks, I am a bear of little brain sometimes, I think I get it.
Antartic sea ice disapeared before 1980″ Was that on some planet from Star Wars? it certainly would be news to the people who actually visted the place before 1980 which included a whole bunch of navy people carrying our researchers to the south polar stations to say nothing of the other nations doing the same thing. You folks seem to just make up things when the data differs from your mindset. The world has warmed slightly in the last one hundred plus years, actually for the last four hundred plus years , the depths of the little ice age. You might ask yourself if you are not religious about AGW why the little ice age occured, the volcano theory just was blown out of the water so you need to find another. It was world wide as that forest under that melting glacier in Alaska demonstrates so that will not work saying it was northern europe only dispite a whole bunch of papers from all over. You might than consider the medievil warm period, warmer than today, at least two peer reviewed studies. All that occured with half todays CO2 levels. CO2 changes did not change the climate than and as shown by the Mauno Loa NOAA study not today either, zero correlation with climate change which has not actually changed in 16 years. The wild weather in the US per the weather service is a figment of your imagination, it is normal weather and per NOAA the average US temperature has dropped a bit since 1998 As for the temperature record that was 1936 per NOAA.