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In 2012 I put together a storify using twitter and weblinks about the  Greenland Surface Melt. In that story a bunch of climate scientists and I talked about whether the extreme melt seen in  2012 was a signature of global warming.

Greenland melt on the BBC

The original BBC Greenland Melting story

An Open Access paper by Sirpa Häkkinen and others Greenland ice sheet melt from MODIS and associated atmospheric variability, published on 10 March 2014, explains how it happened.

It is a clear and well written paper that shows using MODIS (Moderate Resolution Imaging Spectroradiometer) data from satellites that you need two things for a serious surface melt event: atmospheric blocking (which allows warm air from the south to go over Greenland) + warm surface temperatures.

The event in 2012 had both of those conditions whereas 2013 did not. The difference is striking in their Figure 1.

Häkkinen et al., 2014 Fig 1

Figure 1 From Häkkinen et al., 2014. Extent of melt on the Greenland ice sheet for (a) 1 January to 31 December 2012 (days 1–366) and (b) 1 January to 30 August 2013 (days 1–243) as determined from MODIS-derived melt maps. A maximum of ~95% of the ice sheet surface (shaded red) experienced some melt in 2012 and only ~49% of the ice sheet surface experienced some melt in 2013. White represents no melting (according to MODIS), and green represent non-ice covered land areas. The location of Summit, mentioned in the text, is shown. Elevation contours are shown at 1500, 2000, 2500, and 3000 m.

Their data set allows them to go back to 2000 and construct annual time series.

And just like Dr Ruth Mottram said in my original storify,

Ruth Mottram Tweet

Tweet used in original storify.

They find all of the features Ruth pointed out (shown in their Figure 4).

They say,

"that June-July 2007 had the most blocking days but did not have the largest melt, although 2007 has been identified as a large melt year in a seasonal sense"

The reason it did not have as much surface melt as 2012 is because the air temperatures brought over the ice sheet by the atmospheric blocking "barely reached 1.5 SDs [above the summer average temperature]". (SDs means standard deviations - basically a measure of how variable the temperature is about the mean.)

In 2012 the atmospheric blocking brought in "a  long-lasting anomaly of 2–2.5 SDs [above the summer average temperature]". This is a bit bland but 2.5 SD's in this data set corresponds to temperatures ~6°C or greater above the summer average on the surface of Greenland. That is why the melt in 2012 was so large.

Häkkinen et al. (2014) make no comment in the paper about the future, or the impact of anthropogenic climate change on such events over Greenland. Looking at various assessments of the scientific literature (e.g the Arctic Report Card) we may draw our own conclusions about whether to expect more of these melting events.

It's very common to hear people harking back to the time when everything was apparently "better". Before the planet was "ruined", before anthropogenic climate change kicked in, and when everybody treated each other with respect.

Of course I don't hold that view.

Polar exploration had a golden age of sorts which is usually called the Heroic Age. It covers the time period when explorers like Mawson, Shackleton, Speirs Bruce and Scott headed South.

I am interested  in the time period before that too.

The British Library have put over a million images on Flickr. With that sort of resource surely there is something polar before the Heroic age?

Searching on the term "Antarctic" throws up a vast number of results -and a couple immediately caught my eye. They were pictures drawn by one of my new favourite artists: the Scot William Gordon Burn Murdoch.

Ever since I started researching and writing about the polar regions I have always been struck by how people seem to imagine them as some sort of "untouched wilderness". This image naturally caught my eye.

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I am working on a polar oceanographic problem at the moment, but the beauty of physics is the principles are universal. That means you can end up reading widely. I came across a very interesting paper (to me):

Gaining insight into Clipperton's lagoon hydrology using tritium

2009 paper in Estuarine, Coastal and Shelf Science

Through the joys of open access a PDF of the paper is available on the Ifremer Archimer institutional repository.

Whilst reading the paper I quickly skimmed over the PDF to see if I was on the right track for what I was interested in. It looked good so I went back to the beginning and starting reading in more detail.

Introduction paragraph 1:

"Clipperton island got the reputation of being one of the most obscure, isolated and
unpleasant places on earth"

I thought "eh?" I like a bit of unpleasantness but...

So I read on...  The paragraph gives a quick history of the occupation of Clipperton Island. It was first occupied as part of the phosphate mining industry. But it doesn't have a happy history.

"In this tiny tropical hell, many became desperate to leave, convinced that the island was driving them mad. During World War I, the islanders were cut off from the mainland and died little by little from scurvy and malnutrition. The survivors, a handful of women and children, became ruled by a madman (the light keeper) who proclaimed himself “King of Clipperton”, raping whomever he wanted and murdering any who resisted. Eventually, the women killed him, putting his reign of terror to an end. By July 1917, three women and eight children were the only ones alive and were picked up by the USS “Yorktown”. Its last permanent occupation was in 1944/45 when President Roosevelt ordered the US Navy to seize the atoll. Soon after World War II ended and the atoll was abandoned"

Philippe et al 2009.

Scurvy, malnutrition, rape and murder. I don't come across that sort of thing very often in the area of oceanography I research.

Clipperton Island is about 580 nautical miles off the coast of Mexico.

There is a very good Wikipedia page on Clipperton Island. This is quite surprising given that the atoll is only 6 km2 with a maximum elevation of 29m. It seems to be pretty regularly visited by members of the amateur radio community, and there was a private expedition there in 2013.

If you are interested in the Law of the Sea it seems that in December 2010 the French claimed an exclusive economic zone around the island under the provisions of the United Nations Commission on the Limits of the Continental Shelf (CLCS).

That would mean this 6 km2 atoll has given the French a territorial claim of 1.52 × 109 km2 of sea bed in the pacific and the ownership of the resources there.

Not bad for a place that can barely sustain human habitation.

And the stuff in the paper about tritium was pretty good as well.

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Last week the Royal Society (UK), and the National Academy of Sciences (NAS) released a good PDF booklet called Climate Change: Evidence & Causes.

In the words of the US NAS

"Climate Change makes clear what is well-established and where understanding is still developing. It echoes and builds upon the long history of climate-related work from both national academies."

You can read the background at the Royal Society site, and Carbon Brief provides a synopsis so good I can't add much.

But I will talk about the cover. Here is a screen grab.

The Cover of the Royal Society Climate Change report

The Cover of the Royal Society Climate Change report

I think it's beautiful. I love the way the golden light reflects on the young sea ice. In fact I think it is so beautiful that we used it on the cover of a book I partially wrote and edited for my employer in 2011.

The Cover of the Open University Frozen Planet Coursebook

The Cover of the Open University Frozen Planet Coursebook

The original is an iStock image called "Polar bear on ice close to golden glittering water". Now that is not what I would call it - but then I wasn't fortunate enough to be in a helicopter at that time of the year, and so I don't get to choose.

The Royal Society / NAS had cropped the bear from the image so they used the segment in the yellow rectangle below...

S175 Cover with Crop

The cover of the S175 Book with the crop

They actually rotated and stretched it slightly to completely miss the bear - although there are still clearly bear footprints in the version they use.

I am sure they did that because they did not want to get into the whole "poor polar bear looking over the melting ice" conversation. All the way back in 2012 Carbon Brief included "sad polar bear on melting ice" as one of their Nine climate change pictures I really don't need to see again.

So why did I use it? To me the polar bear is in its natural habitat. The bear is wandering over decaying sea ice and refrozen melt water. Our book is filled with the science of how and why the ice grows and melts, and what adaptations and strategies the animals use to survive, plus lots of other science. The polar bear's Latin name is ursus maritimus - which in English is "sea bear": open water and ice are part of their habitat.

That nuance is not possible in a short but excellent PDF report on climate change, so

I imagine they chose the beautiful light.

In hindsight I think I would have used another image. But only because if you go to the trouble of writing a book, then you would want to keep it special.

The problem I had at the time was that I was not very good at choosing any of my own images.

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The title of the post points to the book Setting Free the Bears by John Irving. It's a book I like and it is about two young people releasing the animals from Vienna zoo after the Second World War.

In a previous post I showed the temperature cycle on the Antarctic Peninsula, and pointed out that the monthly mean atmospheric temperatures show that it is actually surprisingly moderate.  Whether you consider the temperature cycle moderate or not, the cold temperatures and strong winds drive an amazing amount of seasonal sea ice production.

This plot shows the average seasonal cycle of Antarctic sea ice extent against date.

Seasonal cycle of Antarctic sea ice extent

Seasonal cycle of Antarctic sea ice extent

The daily average extent is calculated from the satellite record from 1981-2010, and the grey shading either side of the line is the standard deviation.

Here are three obvious things to pick out of this plot.

  • Antarctic Sea Ice extent varies a lot: From 2.9x106 km2 in February to 18.6 x106 km2 in September. This is a range of 15.7 x106 km2.
  • The seasonal cycle is not symmetrical: There is a slow growth followed by a relatively rapid decay.

To really get an idea of what this asymmetric growth / decay pattern looks like watch the following you tube clip a few times. (The data for the movie is from the AMSR-E Satellite and it is from Climate Central.

So slow growth, and then rapid retreat. Ice tends to advance away from the continent, but as it retreats it can melt first within south of what you would consider the ice edge.

How the Antarctic sea ice extent is changing is for a future post, but it is currently increasing. There are significant regional changes over the duration of our satellite record. For a couple of good accesible comments on the trends in Antarctic sea extent you could read Professor John Turner in the Guardian, or Tamino on the Antarctic Sea Ice increase.

Data source

The average sea ice extent is part of the National Snow and Ice Data Center (NSIDC) Sea Ice Index.

Fetterer, F., K. Knowles, W. Meier, and M. Savoie. 2002, updated daily. Sea Ice Index. Daily Sea Ice Extent Climatology. Boulder, Colorado USA: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5QJ7F7W.

The actual file I used is downloadable from this FTP location.

 

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In the previous post I made a plot of Antarctica and compared it to the size of Europe. I made the throwaway point that it was unreasonable to imagine Antarctica as being characterized with one climatic zone. It is not all the "coldest and windiest place" on Earth.

I thought a simple example would show what I mean:

I got the mean monthly temperatures at two Antarctic Stations from the NOAA NCDC GCPS MONTHLY STATION data available from IRI/LDEO Climate Data Library.

I chose Adelaide Island and Vostok, and picked monthly data from December 1964 to December 1966.

Adelaide Island and Vostok mean monthy temperature

The mean monthly temperature at Adelaide Island and Vostok station

Adelaide island is on the coast and it astonishingly beautiful. The data I used were collected at the British Antarctic Survey BASE T.

In contrast Vostok station is quite literally an icy waste in the middle of nowhere (* but see below).

This plot shows their relative locations in relation to the South Pole.

The locations of research stations

The locations of Adelaide Island, Vostok, and South Pole

You can see that at Adelaide Island - which is at sea level and coastal - the seasonal cycle is relatively narrow and only about 11°C. Temperatures are above 0°C in the summer.

At Vostok - which is on the East Antarctic Ice Sheet and at an altitude of about 3700m - the seasonal cycle is vast. In the Antarctic summer the temperatures are about -30°C, whereas in winter the temperatures fall and it is scarily cold (monthly mean -71.4°C in August 1966!).

If you want to know why Adelaide Island has a relatively small seasonal cycle, whereas Vostok seems to have a squashed "U" shape temperature cycle, then you have to understand something about the basic meteorology of the Antarctic Regions. (As an aside then you would understand why this happens in winter).

In a later post I may say something about how the climate is changing across Antarctica over the last 50-60 years. The spoiler on that is at on the Antarctic Peninsula it has changed a lot  - in the range "4-5°C",and the changes are impacting the ocean system, whereas at Vostok it has not.

* - of course Vostok isn't really in the middle of "nowhere". It is over the vast and hugely significant under ice Lake Vostok, and is the location of the first great Antarctic ice core - the Vostok Ice Core.

 

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I keep seeing a map of Antarctica with an overlaid outline of the United States. I thought it would be helpful to have a picture of the continent compared with the size of Europe.

Antarctica and Europe

Antarctica compared with the size of Europe

This is a picture from a book I wrote half of and edited a long time ago.

It always struck me as strange that Antarctica being the "coldest and windiest place" is constantly recycled. The picture shows it is a huge place and it does not have one single climate.

On the Antarctic Peninsula it is relatively mild. It's even referred to sometimes as being the "banana belt". But away from the heat of the ocean, and high on the plateau it is without doubt cold almost beyond comprehension.

But one thing is for sure: there is no representative Antarctic climate.

 

I don't usually work on this sort of thing, but very recently I have been writing about hazards caused by the cryosphere. A major hazard is of course the avalanche - whether ice, snow, or a mixture.

This video was posted on You tube (with the tag line "Courtesy Vertical Solutions"), and it shows the impact of a snow and ice avalanche on the Alaskan road network on the 26 January 2014.

 

I tweeted it yesterday and the glaciologist Mauri Pelto replied

 

I'll try to remember to keep an eye online to see the outcome.

 

 

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I came across this brilliant Deep Sea News blog post about oil on troubled waters. It talks at length about how a surface film of oil damps out higher frequency surface waves and only the low frequency waves can propagate. The net effect is the sea feels calmer as the breaking waves are damped out.

The same thing happens in rough seas when ice forms. I took the picture below in Bellingshausen Sea.

A grease ice slick in the Bellingshausen Sea Antarctica

A grease ice slick in the Bellingshausen Sea Antarctica

What you are looking at is very thin slick made up of sea ice crystals in the open ocean (called grease ice). The layer of crystals only allows the low frequency waves to propagate - so you see these odd looking slowly propagating ripples.

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