How does a glacier melt underwater?

This post was first published on the ice2ice blog though I have extended and expanded it with some extra details.

 Ice2Ice is a large project funded by the European Research Council in a Synergy grant. It is one of my current main sources of funding and is a pretty exciting piece of work, looking at abrupt climate changes in the past (when the temperature around Greenland suddenly increased by around 10-15C in about a decade) known as Dansgaard-Oeschger cycles.  Go and check out the webpage and also this very nice overview on science nordic including cool film showing ice core processing

Glaciers in Greenland lose mass by melt and runoff, by calving and by submarine melt that happens at the front of outlet glaciers that terminate in the ocean. Submarine melt occurs because the ocean water is (relatively) warmer than the ice, but it goes much faster where there is turbulent water mixing the layers by the glacier. Probably the most important source of turbulence are plumes of water that emerge at the base of the glacier where it terminates in the fjord. Penny How, a scientist at the University of St Andrews recently wrote a very nice blog post giving an overview. Including this nice GIF showing a very clear plume coming out the front of Tunabreen, a glacier in Svalbard:

tuna_plume
Note the dark coloured water (indicating high sediment concentration) coming out the front of Tunabreen in Svalbard – Image by Penny How 

The water is generated by melting mostly at the surface though also at the bed of the glacier. Meltwater flows like rivers through systems of englacial channels to finally arrive at the bed where it makes its way, eventually, to the end of the glacier.

Unfortunately these channels are pretty hard to map, and there are lakes and areas at the bed where water can be stored. The plumes themselves are rather hazardous to observe as they are often inaccessible and in front of actively calving sections of the glacier. There have been a few studies, but often these are snapshots in time and it is difficult to assess how important these processes are to the overall mass budget of the ice sheet.

Therefore we have to turn to models to work out how important plume processes are for submarine melt. In our recent paper with Slater et al (2017), we contributed data from the HIRHAM5 RCM to look at runoff within a catchment in Greenland. The case study was based at Kangiata Nunata Sermia glacier, in the Godthåbsfjord area of south western Greenland. It’s a relatively accessible glacier showing many of the common processes for Greenland outlet glaciers and has a fair bit of data available. The Langen et al (2015) paper showed that HIRHAM5 performs pretty well in terms of modelled runoff in this region as I detailed in this post.

The modelled runoff was used in two different models of subglacial plumes, including one implemented in MITgcm, in order to determine what configuration of subglacial hydrology and plume distribution along the ice front was most likely.  The models were compared with a time lapse photos of the ice front showing plume activity at the surface.

slater_meltwaterplumes
Illustrations of plume state classification. a) Plume state = -1, ice tongue present. b) Plume state = 0, no ice tongue and surface expression of a plume. c) Plume state = 1, plume visible adjacent to glacier terminue but is contained within a few hundred metres of the trerminus. d) Plume state = 2, plume visible and flows down-fjord at surface for a number of kilometres. 

For a large proportion of the summer, the modelled catchment runoff greatly exceeds the discharge required to create a plume that would reach the fjord surface, yet there are extended periods when there is no plume visible from the time lapse pictures. This can only be explained by the runoff emerging into the fjord in a spatially distributed fashion. In the paper we therefore argue that subglacial drainage near the glacier terminus is often spatially distributed, formed either from numerous point sources of subglacial discharge, or a single but very wide subglacial channel or possibly a complex combination of the two.

There are two implications from this work. Firstly, a more spatially distributed submarine plume gives a higher total melt than a single concentrated plume but this melt rate is still unable to explain the mass loss at the terminus when considering the ice velocity at the terminus, suggesting that calving is still the most important mass flux term at this glacier. Secondly, the modelling study found that the distributed hydrology, suggested by the results leads to a more direct ice flow response to high surface melt rates and this response most likely scales with catchment size.

Probably the most important result to come out of this study is that longer time series of observations of plumes, in combination with the modelled runoff lead to a dramatically different understanding of key processes within the fjords when compared to those suggested by simple snapshot observations in earlier studies.

slater_meltwater_runoff
a) Air temperature from KNS1 and NUKL PROMICE stations b) Modelled runoff. HIRHAM5 (orange) delays runoff using a parameterisation based on surface slope. PDD model (green) assumes instantaneous runoff. PDD delay (pink) uses a transit velocity of 0.05 m s-1 from point of production to the terminus. PDD rapid (purple) uses a transit velocity of 1 m s-1. the green curve has been smoothed using a 3d moving window, the pink and pruple curves using a 6 h moving window. large discrepancies between HIRHAM5 and the PDD model arise due to rainfall events (e.g. days 177 and 181). c) KNS1 daily ice velocity. d) Plume state as described in the picture above. 

So, does this matter – well, probably. These kind of studies sprang up in the wake of a paper published by Eric Rignot and friends. They were almost the first to really look seriously and consistently at the amount of ocean-driven melting going on at these fronts in Greenland and they found summer melt rates at a number of glaciers that would indicate almost as much mass loss as from calving rates. Out of this early work, the NASA funded OMG (Oceans Melting Greenland) project emerged, which is currently contributing a huge amount of data that will be very useful – including the bathymetry of many fjords in Greenland which are still in general rather poorly mapped.

This focus is welcome, the ice sheet-ocean interaction is incredibly poorly observed and we are very much reliant on imperfect models. However,  our study shows that meltwater driven plumes and melt rates at the front of this glacier is rather a small source of glacier retreat when compared to calving rates or surface melt and runoff. Calving is important because a large amount of ice can be lost very quickly as these bergs show. These calved off the front of the same glacier as in this study but in 2009 when I happened to be in Greenland. the glacier, Kangiata Nunata Sermia was previously called the Godthåbs glacier, after the earlier Danish name for the town of Nuuk. It is also often known by the abbreviation KNS in the scientific community.

2009-08-24-greenland-264

 

If this process is similar elsewhere in Greenland it suggests that submarine melt may be less important to rates of ice mass loss and consequent sea level rise. This is not to say it is not important elsewhere in Greenland, and indeed under climate change scenarios with enhanced melt and much warmer ocean waters making it way into the fjords, this may well change and could potentially become much more important.

2009-08-24-greenland-small-camera-025
The mass of icebergs that are calved from the front of Kangiata Nunata Sermia 

Sea Level Rise: How far, how fast?

A paper appeared in Science this week about sea level rise in the last interglacial (about 129-116,000 years ago). It has sparked the usual predictable headlines as it points out that during that period, sea level rose by about 6-9 metres but that that the ocean temperature as far as it can be reconstructed, is about what we see now, that is about 0.5C warmer than the preindustrial.

sealevelguardian
Guardian reports on latest study

In a sense this isn’t that “new” – we’ve known about higher sea levels during the last interglacial for ages and that the global mean temperature was roughly 2C above the pre-industrial global mean. This is in fact one of the reasons for the Paris target (though some scientists speculate that it’s also pretty much already out of reach).

However, the sea surface temperature stuff makes it extra interesting as the ocean is a pretty big source of uncertainty in global climate models and mot models do not manage to reproduce modern day ocean temperatures all that well.

It should also be said that the last interglacial is only a good analogue for 2C world up to a point – it was warm because of enhanced solar input, not because of greenhouse gases as this plot from an Antarctic ice core, edited by the awesome Bethan Davies at the Antarctic Glaciers blog shows:

vostok_420ky_4curves_insolation_to_2004
Carbon dioxide (CO2), Methane (CH4) with reconstructed temperature from the Vostok Ice Core, taken in Eastern Antarctica. Enhanced with modern methane, CO2 and temperature measurements by Bethan Davies. Note that the “modern” value of CO2 here is from 2004. In 2017 it is currently measuring 403 ppm.

It’s also interesting to speculate where the water came from – the Greenland ice sheet was much smaller than today but it was still there and now “only” contains 7m of sea level rise today. So the complete disappearance of Greenland cannot explain the rise in global sea level. The small glaciers and ice caps of the world can’t contribute more than half a metre or so either. Therefore it has to be Antarctica contributing the most – East or West is the question and it really is a very very longstanding question.

The progress in the international polar year (IPY) in mapping the bedrock of Antarctic in the BEDMAP2 brought quite a few surprises, including the discovery of several very deep marine basins in the East that could potentially contribute a lot of water to sea level.

More recently, channels under the floating ice shelves of west Antartica, along with various modelling studies have proposed that the west could be much more unstable than thought. Actually this has been a very very longstanding problem in Antarctic science since at least the late 1970s when John Mercer first proposed the marine ice sheet instability hypothesis.

In any case, events in both Denmark and the UK have brought this problem home more sharply.

stillstormflod
The silent storm surge – coastal flooding in Copenhagen on the 5th January – the water in the harbour is not normally this high! Source: Brian Dehli, shared by DR 

aslaktweet

The “silent storm surge” in January 2017 around the coast of Denmark was  a hundred year event in many places, but as Aslak Grinsted points out, sea level rise makes a hundred year event a 20 year event with only a small rise.

Sea level will not rise equally everywhere, the fingerprint of Greenland ice sheet loss is felt largely in the Pacific, Antarctic ice melt will be felt in Europe. It matters where the water comes from. A point not generally appreciated.

So this new paper is also important, but it only underlines that we need to be able to make much much better estimates of how fast and how far the ice sheets will retreat, which is the justification for much of my own scientific research.

Finally, I think it’s probably necessary to point out that sea level is already rising. This was asked by a listener to Inside science, one of my favourite BBC radio 4 programmes/podcasts. I was a little surprised that an apparently scientifically literate and interested member of the public was not aware that we can measure sea level rise pretty well – in fact to an extent, the global warming signal is more easily detected in the ocean than in the global temperature record. This is because the ocean expands as it warms and there is ocean pretty much everywhere, whereas temperature observations are patchy and mostly on land. Clearly, scientists like myself are *still* not doing a very good job of communicating our science more widely. So here is the global mean sea level record to date, it’s updated pretty regularly here and on average, sea level is rising at about 3mm per year or 3cm per decade.

 

sealevel
Sea level variation measured by satellite since 1993 from NASA

When we look at tidal gauges,sea level rose about 20cm in the 2oth century

20crsealevel
Sea level rise in the 20th century measured by tide gauges, plot by NASA, data from CSIRO

The big uncertainties we have on whether or not this will accelerate in years to come is largely down to missing processes in ice sheet models that we don’t yet understand or model well – mostly calving by glaciers and ice shelves. I promised Steve Bloom a blog post on that at some point – I have a paper to finish and new simulations to run, but hopefully I’ll get round to that next.

UPDATE: I was made aware this morning of a new report from the European Environment Agency about climate change impacts and adaptation in Europe. In the report they state (correctly) that while the IPCC 5th Assessment Report suggested that in the 21st century the likely sea level rise will be on the order of half a metre, some national and expert assessments (I took part in a couple of these) had suggested an upper bound of 1.5 – 2m this century, for high emissions scenarios.

This is a big difference and would be pretty challenging to adapt to in low-lying countries like the Netherlands and Denmark, not to mention big coastal cities like London or Hamburg. It’s laso important to emphasise that it doesn’t jsut stop at the end of the century, in fact our simulations of the retreat of Greenland ice sheet suggest it’s only just getting going at the end of this century and the next century the rate of ice loss will really start to accelerate.

All of which is to say, there’s really a very good reason to act now to reduce our emissions. The EEA has also produced this very nice map of observed sea level rise in Europe over the last two decades based on  Copernicus environmental data.

Obs_slr_Europe.png
Check out how much the sea level is rising where you live… Source: European Environment Agency, data from Copernicus Marine Environment Monitoring Service

With the prospect of American federal funding for environmental observations being reduced or strongly constrained in the future, it’s really important we start to identify and support the European datasets which are the only other sources of environmental monitoring out there right now.

 

 

The Unicorn and The Lamprey

On the 16th may 1619 two ships, the Unicorn and the Lamprey, set sail from Copenhagen searching for the fabled North West Passage. On board there were 65 men, led by their captain, the Danish explorer Jens Munk. A year and a half later, the Lamprey limped back into Bergen (Norway) with just 3 men, including Munk, on board.

Almost all of the other crew members had died of scurvy in Hudson Bay .

The story of this terrible voyage, their sailing round Iceland, Greenland, Baffin Bay and into Hudson Bay is outlined in this wonderful atmospheric podcast from DR.

jens_munk_map_1624
A Map, hand-drawn by Jens Munk in 1624 of the area between Cape Farewell and Hudson Bay, seen from the north; (Source: Tromsø University library)

The UK has similarly many tales of Arctic and Antarctic suffering, listening to the podcast I was put in mind of Coleridge’s famous “Rime of the Ancient Mariner”, but we rarely hear of the similar stories from other nations, a clear benefit of learning other languages is being able to access these archives and stories*.

The podcast contains a wonderful description by a Greenland pilot of the sea ice and how tricky navigating it can be along with interviews and inputs from many others. If you are at all familiar with Danish – I really recommend the series.

However, the description by a nutritionist of the terrible effects of scurvy had me wondering. I learn (via Dutch family and confirmed by the OED) that the name of the disease, caused of course by a lack of vitamin C in the diet, is probably from the Dutch Scheurbuik – rip belly – an eloquent description of one of the notable later stages of the disease.

Rip here is less a description of enhanced musculature and much more a description of what it feels like when your internal organs start to bleed and your muscles and bones are weak from lack of nutrition.

asm-30-325-g002
Photo of chest cage with pectus excavatum and scorbutic rosaries – from this paper

Upon looking it up (Thankyou Wikipedia), I learn that the causes of scurvy had been repeatedly identified, forgotten and mistaken since at least the middle Ages. There is an estimate that around 2 million sailors died as a result of scurvy between 1500 and 1800.

2 Million almost entirely preventable deaths and 2 million men who died in appalling agony.

And this happened in spite of what appears to be the first recorded medical trial by James Lind in the 1750s, it still took the Royal Navy 40 years to start giving out fresh citrus fruits as a standard on their ships. Vitamin C itself was only finally recognised and extracted in 1932.

This story is an outrage in many ways, but a clear example also of how science and medicine, properly conducted, can help to improve and save lives. It is also a clear warning to conduct thoughtful experiments with care and to listen to those warnings when they have been issued.

It might also be a recommendation that learning foreign languages is not only fun and useful but can be it’s own reward.

*I should also mention here that the rather awesome Danish Arctic Institute are currently producing a very well written series on Danish exploration in the Arctic in English, based on their own very comprehensive podcast series. These are published online in the Arctic Journal. Both the series of historical accounts and the newspaper in general are absolute top recommends for those interested in the subject of the Arctic environmentally , socially and politically.

dsc_57
The lure of the poles (Svalbard in Spring, the coldest time of year)

Extract from “Rime of the Ancient Mariner” by Samuel Taylor Coleridge

…With sloping masts and dipping prow,
As who pursued with yell and blow
Still treads the shadow of his foe,
And forward bends his head,
The ship drove fast, loud roared the blast,
And southward aye we fled.
And now there came both mist and snow,
And it grew wondrous cold:
And ice, mast-high, came floating by,
As green as emerald.
And through the drifts the snowy clifts
Did send a dismal sheen:
Nor shapes of men nor beasts we ken—
The ice was all between.
The ice was here, the ice was there,
The ice was all around:
It cracked and growled, and roared and howled,
Like noises in a swound! …”

 

Climate change at the local scale

UPDATE: The presentation from the meeting is now here (pdf): SFWI_pres_for_sharing.

I have tried to list all the different people and websites that provided material for this presentation, but if I have forgotten anyone, please do let me know and I will be more than happy to add an acknowledgement. 

Normally I work on the continental or hemispheric scale, concentrating on Greenland and the Arctic. Next week, I have a new challenge, to go much more local than that, to the country and even county scale.

I have been asked by the Staffordshire Federation of Women’s Institutes to give a talk on Climate Change next week. A rather broad subject!

The WI is a very long-standing and well-established institution in the UK and my mother, (who is of course the one who roped me in to it) has been a member since I was tiny wee thing. Outside the UK the WI are probably mostly known from the very successful film Calendar Girls.

These inspiring women have showed themselves to be a formidable lobbying force over the years and subjects as diverse as bees and pesticides to care for people with dementia and the plastic bag tax. Years ago, I recall my mother coming home from a WI meeting and talking about the ozone hole, one of the earliest organisations to start talking about it, so it is not a particular surprise they now have a focus on climate change. They now have a climate change ambassadors programme.

WI_inspirations
Some of the many successful WI campaigners over the years from

Each area has to organise themselves and decide what they would like to do as part of this, so as partly a kick off to that process and as part of their science committee activities (It’s not all Jam and Jerusalem at the WI these days apparently) I will be presenting in Stafford at the county council chambers on the 6th July 1.30-3.30pm.

CountybuildingsChamber
The Staffordshire County Council chambers

As part of the programme, Staffordshire County Council will also be sending a representative to talk about how the County is responding both in terms of managing impacts and reducing emissions towards achieving the UK’s targets.

It’s going to be interesting talking about climate change both observed and projected in the UK, happily, the UK Met Office is a world leader in this and the very friendly Mark McCarthy has provided me with a bunch of data to distil down and prepare some visualisations from (see graph below for a quick and dirty look at some data)

I also plan to talk about the basic science of climate change, how it has developed, how it is observed and how we make projections and what we expect for the UK and Europe over the next decades to centuries. I have called it questions and answers since I hope that people will ask questions as we go through. From talking to people everyday, it’s clear there are a lot of questions people have about climate change and the impacts and the sciense. I also hope to talk about some of the options we have for tackling emissions and how to deal with the impacts. Copenhagen is a great case study for both of these elements. This is quite a lot for a short hour or so talk, but let’s see how we get on!

Staffs_Temp
A quick and dirty plot of avergae observed temperatures in Staffordshire (annual and seasonal means 1910 – 2015/2016) with thanks to UK Met Office and Mark McCarthy for providing the data.

It’s open to the public so if you happen to be at a loose end on a Wednesday afternoon and fancy it, I believe you can get tickets via the following secretary@sfwi.org or telephone 01785 223838.

In the mean time, should any members of the WI or indeed other Staffordshire residents who happen to be reading this, have any questions or ideas that they would like addressed specifically, please do feel free to leave a comment or ask me on twitter.

 

 

A Sea-Ice Free Arctic in 2016?

UPDATE: The Arctic Sea ice Outlook I mention in the post below has just been published for 2016. We will follow this up in September when the final results will be known, but here are the 30 entries using a rage of different techniques including sophisticated computer models, statistical estimates and what is kindly called “Heuristics” but which may be characterised as an educated guess by people who have been studying this field for a while…

sio_2016_fig_1_30june

Professor Wadhams has not contributed an estimate this year but it can easily be seen that none of the estimates reach as low as the putative 1 million square kilometres. Nonetheless the view of 27 expert climate scientists put forward by Kay, Bailey and Holland (pdf), not to mention the very sophisticated RASM model (one of the most sophisticated in this area, run by the US Naval Postgraduate school), put the September extent at a very low 3-4 million km2, in the same range as the record low of 2012.

It will be interesting to see how low it does go. The latest results from the polar portal show that Arctic sea ice is currently still on the record low 2012 line but a careful look shows also that the 2012 and 2013 curves diverge around mid to late June. The year 2013 is pretty representative of a “new normal” over the last 4 years or so, it is therefore difficult to tell based on simply extrapolating along the curves which path 2016 is likely to follow.

SICE_curve_extent_LA_EN_20160711.png
The area covered by at least 15% sea ice in the Arctic from 1981 to present, the black and red curve shows the year 2016 and is updated daily on the Polar Portal 

The current weather plots on the Polar Portal (based on weather forecasts produced by the European Centre for medium Range Weather Forecasting, probably the best numerical weather model in the world) show no unusual temperatures in the Arctic Ocean right now, though parts of Arctic Canada and Siberia certainly look warm.

Wthr_Anom_SM_EN_20160711.png

We’ll have to wait and see until September…

Original post below from June, 14th, 2016. 

The Polar Portal has become part of our daily life at DMI where I work in the last few years, it combines detailed observations and models from the Greenland ice sheet, the Arctic sea ice and, soon hopefully, permafrost. I am particularly involved in the Greenland pages where we daily calculate the amount of snowfall and snow melt which gives us a surface mass budget and which we sum up over the year to work out what it means for the health of the Greenland ice sheet. This year has been especially interesting with an extraordinarily early start to melting driven by warm Arctic temperatures. Many records in Greenland have been broken in April, May and June. Spectacularly, last week Nuuk set a new temperature record for June that managed to last only 24 hours, before it was broken again.

This is the new reality in the Arctic. And it is also having an effect on sea ice. The Arctic sea ice extent has long been used as a bellwether of climate change with much effort exerted by both activists and sceptics in trying to prove or dismiss claims about climate and its effects on sea ice.

DSC02322.JPG
Crossing the sea ice in front of Paulabreen, a surge type glacier with a calving front in Svalbard

I trained as a glaciologist originally,  but even then I came across sea ice and was first of all unnerved by it, crossing on scooters to visit glaciers in Svalbard, and then fascinated by it. Recently I have been working pretty closely with my colleagues in DMI who are sea ice scientists and I have learnt quite a lot. We even published a paper together in the journal Polarforschung earlier this year. Not only that, I am now part of a big ERC Synergy project known as ice2ice  with scientists at four institutions in Bergen and Copenhagen working on the complex connections between sea ice, ocean, atmosphere and ice sheet in the Arctic. More on that another time, but suffice to say it’s fascinating work and I know a hell of a lot more about sea ice than I did even three years ago.

So when this news story crossed my email this evening courtesy a BBC researcher and journalist I knew pretty well straight away what it was about. Basically the scientist Professor Peter Wadhams had made some statements about the extent of Arctic sea ice which might be considered somewhat eyecatching.

Capture-wadhams

Professor Wadhams is a well-known scientist who did some incredibly valuable and indeed ground-breaking early work on sea ice. More recently he has also done some very valuable work reconstructing thickness based on submarine observations during the Cold War (see below on why this is important). I well remember seeing him talk about this as a young graduate student, he is an excellent speaker and gave a very interesting and compelling talk. In the last few years he has made several statements that have been widely reported and perhaps misinterpreted, with regard to the future fortunes of the Arctic sea ice.

Now, I need and want to be clear about this. Most of the global climate models we use are not very good at reproducing the observed historical sea ice extent. They have improved significantly in the last few years but still struggle to reproduce the actual observed decline in sea ice area from satellites. And there are actually very good reasons why this should be. There are some very good stand alone sea ice models which have done a very good job and the key difference between these models is our clue. Sea ice models are generally partly forced with actual observations, or climate reanalyses which assimilate observations, so the atmosphere and the ocean are close to reality. Basically sea ice responds to weather, and if you have a more accurate weather driving your sea ice model you will get a better fit to the observations.

So, is Professor Wadhams correct? Will the sea ice “disappear” this year.

Well, it is pretty clear that given the changes we have already observed in the Arctic, as well as what we know about Arctic amplification and the general direction that anthropogenic emissions are heading in, that unless something changes pretty soon, we will likely see an end to a significant cover of sea ice in the Arctic at some point in the next few decades. But was does that actually mean?

Reading his actual comments in the article he appears to define 1 million km2 as “no sea ice” and that partly reflects how we define sea ice extent. Since most of the data sets use a cut-off figure (typically 15%) to define when a grid square or pixel is or is not a sea ice point. This is known as sea ice concentration and is really something of a hangover from the days when sea ice was observed from ships and an attempt was made to estimate how much sea ice in the area  was around the vessel.

There are however lots of things that can affect sea ice extent, including winds and currents and melt ponds. The latter also affects how different algorithms assess the area that is or is not covered by sea ice. As there are a number of different sensors in use and a number of different algorithms processing that data, it is not entirely surprising that there actually a number of different estimates (I will use OSISAF) for how much of the Arctic is covered in sea ice. And this number will vary in years with more winds for example, or stronger ocean currents, sea ice will disperse faster. It is quite likely that much of the variability in sea ice area in recent years is at least partly attributable to different winds, as well as, for example in 2012, big storms that have arrived at just the right moment (or wrong one depending on how you look at it), to break up the sea ice into smaller, more easily transportable pieces.

As an aside, a better measure for how much Arctic sea ice there is actually present is sea ice volume. Unfortunately this is very difficult to measure, especially outside the winter freeze up season, though a research group at the UCL, centre for Polar Observation and Monitoring have developed a way to do so. Here for example is the most recent plot, which as you can see has not been updated since May 2016 due to the presence of melt ponds on the surface of the sea ice which the Cryosat radar cannot penetrate.

So 1 million km2 is probably a reasonable cut off for assuming an “ice-free” Arctic in the sense that it indicates that there will still be some sea ice drifting around (it always forms surprisingly quickly when the winter begins) in summer, even if it is dispersed.

Over the last 40 or so years (we have good observations going back to 1979, it gets patchy after that), in September, when the area covered by sea ice is at it’s lowest, that extent has been between about 7 and 9 million km2, more recently that has dropped and 2012, the lowest on record had an extent of about 4 million km2, which you can see on the latest polarportal sea ice chart below.

SICE_mod

I well remember 2012, we had a large melt event over Greenland that year also, but it was still quite a long way from the 1 million km2 quoted by Professor Wadhams. Again, let me be clear, we are pretty sure that at some point on a time scale of a few years to a few decades, the Arctic will become “ice-free” in the summer time. We can predict this, even if we don’t know exactly when, since, as I hope is clear now, sea ice conditions are very dependent on the weather. The weather this year so far, at least this Spring has been very warm and congenial to sea ice melt. The big dive shown on the graph above is no mystery when considering some of the temperature anomalies in the Arctic, as shown also on the Polar Portal.

Nevertheless, the recent plots seem to show that the 2 metre air temperature in the Arctic is returning to close to normal and there is little reason to suppose that will change significantly anytime soon.

meanT_2016

Having said that, weather forecasting has improved massively in the last few decades, a true quiet revolution, but we still do not know how the weather will pan out over the whole of this melt season. I am sure that at some point Professor Wadhams will be proved correct, but we do not know when and it is even possible or rather likely that we will have a few years where we switch back and forth between ice free and not ice free conditions. So, the answer to the question I pose above is probably no. But don’t bet on it remaining so for too long.

UPDATE: I recalled this morning on my way in to work that I had somehow failed to mention the Sea Ice Prediction network. This group of people under the auspices of ARCUS, gather predictions on y´the end-of-season sea ice extent ever year. The call for predictions for the 2016 season is now open. Many different research groups as well as one or two enthusiastic amateurs will post their predictions over the next few weeks. It is an interesting exercise, as you can see based on last year’s report (see also figure below), it is not the first time that Profgessor Wadhams has predicted a 1 million km2 extent in September, and his is the lowest (and least accurate) in the rankings.

figure_5
Downloaded from the ARCUS SIPN website

So keep an eye out on this and if you think you can do better, consider submitting a prediction yourself… 

Endnote: There has been quite an absence of posts from this blog recently. I have been too busy with work, family, travel and more recently the EU Referendum (for which I have been threatening a post for quite some time and may yet get around to before polling day). However, a question about Arctic sea ice has been flickering on the edges of my consciousness for a while now so this was a quick (EDIT: not so quick!) blogpost to try and address it when I should actually be writing something else…

 

How pristine is the Arctic?

“The Arctic is one of the last great pristine ecosystems, a safe haven for endangered species and home to Indigenous Peoples whose lifestyle has survived in harmony with nature for thousands of years.”

This quote in the wake of COP21, extracted  from a celebrity I’ve never heard of (sorry, I’m just not that interested in actors)  raised my hackles as it repeated yet again the idea that the Arctic is “pristine”.

Even without contemplating climate change, it is most certainly not, as the polar portal season report I was vaguely involved in compiling this year made clear.

DSC02183
The “pristine” wilderness of Von Postbreen, Svalbard

There is a whole literature in the humanities on Orientalism and “othering”, about how we define other people and places partly to define what we are not. I’m not sure if there is a term for this narrative of a “pristine wilderness”, let us call it “pristinism ” for want of a better term. But before I list the ways in which the Arctic is not pristine, let me make very clear, I am well aware I also suffer from pristinism, to some extent. What my boss teasingly refers to as “the white disease”, the fascination with snow and ice that makes me want to leave the comforts of house and home and go and live somewhere deeply uncomfortable, and indeed dangerous in order to plumb the mysteries. I have been visiting the Arctic for well over 12 years now, though as most of my work is on  computer, I don’t get the option so often anymore. Maybe that’s a good thing, perhaps the last thing the Arctic needs is more people flying to it.

The ecosystem has been significantly degraded by the loss (hopefully now in reverse) of most of the large cetacean species by commercial whalers. Similarly, walrus and polar bears in Svalbard were almost rendered extinct before hunting was banned. It also appears there were walrus in Iceland when the vikings arrived that, like any polar bear at the present day arriving on Icelandic shores, were quickly dispatched. The Greenland vikings were certainly rich from walrus ivory as their main source of income. Not content with exterminating the walrus the early settlers sent their sheep out and very successfully deforested the 25-40% of Iceland that had been forested, leading to dust storms, soil erosion and the unfortunate inability to build boats to get anywhere else very far away. Deforestation has only recently begun to be reversed. In much the same way Musk Oxen were virtually eliminated from Eastern Greenland by hunting, but then rather too successfully introduced to the west where there has been a population explosion.

Fish stocks have at least been largely preserved in Iceland (sensible given how important fishing is to the economy), but there have been several notorious crashes in different fish species in the North Atlantic and around Greenland. Although, to be fair these latter seem to be at least partly caused by changing ocean temperatures rather than purely overfishing. Then there are the invasive species, largely limited so far to the (admittedly delicious) King crab , an omnivore that will eat everything in it’s path much to the fear of some local ecologists around the Arctic coast of Norway.

And then there are the birds. Different bird species face declining populations due both to loss of habitat outside the Arctic as well as hunting in the Arctic region. I was somewhat surprised, though in retrospect I should not have been, at the very few bird numbers that I saw while on a kayaking trip within an easy boat ride of Nuuk.

DSC03114

I would have seen many more in the Scottish islands, but if a subsistence species is within easy reach of a large town (which in themselves would have been impossible prior to colonisation), it is an inevitable tragedy of the commons waiting to happen. Similarly, seals are incredibly wary and remain as far from people as possible in Greenland, a big contrast to the rather trusting and curious creatures I have been able to paddle very close to around the British Isles. And Heaven help any polar bear that strays too close to any Greenlandic settlements, legal protection or not…

Part of the problem are the difficulties birds have in reproducing. This is at least partly down to the toxic mix of chemicals stored in their fat, which comes out in a rush when these animals and birds have to live on their body fat supplies – as they do each summer when incubating eggs. These eggs also appear to contain high levels of mercury, cadmium, PCBs, organochlorines, dieldrin to mention just a few, with an effect on the developing bird embryos inside and of course anything that eats either bird or eggs.

A report compiled by the WWF in 2006 (pdf) from the peer-reviewed literature lists dozens of such studies like this one.  There are also suggestions that environmental pollution is having a significant effect on cetaceans as well as in seal species.

And this of course is because that “pristine” Arctic has an extremely high concentration of industrial chemicals, heavy metals and other by-products of our manufacturing society. Albeit a long way from most sources of production. I was once fascinated to discover that all sorts of historic events such as the Greek and Roman production of silver (and it’s leaden by-product) could be identified in the Greenland ice cores, as could the introduction of leaded petrol and it’s later phasing out. The atmosphere acts as a kind of distillation column, concentrating these poisons at the top (and bottom) of the world, not to mention the local sources. There are coal mines in Svalbard, aluminium smelters in Iceland and Greenland, the oil + gas fields of Alaska, Newfoundland, Norway and Russia. Not to mention god only knows what hazardous (radioactive?) waste is leaching away from forgotten islands in the Russian sector of the Arctic.

DSC03285
Three polar bears take over an abandoned dog shed for a sleep in the shade, Svea coal mine, Svalbard

In the food chain, the little animals get eaten by the bigger ones, which get eaten by the bigger ones, concentrating and accumulating toxic chemicals all the way to the top of the food chain.

To us.

Because humans are, in the Arctic at least, the top predator.

It is by now well known that with a diet that is high in meat, much of it derived from marine mammals and fish, Inuit peoples in the Arctic have very high levels of toxic chemicals in their bodies, and in their breast milk. Greenlandic women are in fact advised to reduce their traditional foods in pregnancy (pdf) and eat something imported instead. Then some recent research suggested the high rates of Parkinson’s disease in the Faroes may be down to a whale meat rich diet.

Yet at the same time we in the crowded, populated mid-latitudes project our fantasies of a pristine fairy-tale at the top of the world.

Sorry.

The Arctic is very very far from pristine, and if what happens in the Arctic doesn’t stay in the Arctic, the reverse is also true, the Arctic is part of this world for good or ill. There is however, no doubt that it exerts a powerful pull on our imaginations.

There is a reason poor old Ursus maritimus has become the poster children of climate change. Perhaps it’s all the bright white snow and ice, even if the Arctic Report card shows us the browning of the Arctic as snow lies for ever shorter periods at the same time as sea ice cover at the end of summer is similarly declining…

 

From the Arctic report card 2015: "Northern Hemisphere (NH) June snow cover extent and September Arctic sea ice extent. Sea ice extent data for 1979-2014 are derived from the NASA Team algorithm (Cavalieri et al., 1996); ice extent estimates for 2015 are produced from real time data (Maslanik and Stroeve 1999). Bold red and blue lines are 5-year running means of the original snow and sea ice extent records, respectively."
From the Arctic report card 2015: “Northern Hemisphere (NH) June snow cover extent and September Arctic sea ice extent. Sea ice extent data for 1979-2014 are derived from the NASA Team algorithm (Cavalieri et al., 1996); ice extent estimates for 2015 are produced from real time data (Maslanik and Stroeve 1999). Bold red and blue lines are 5-year running means of the original snow and sea ice extent records, respectively.”

I am optimistic but cautious about the Paris agreement at COP21. I hope it will come in time to preserve some remnant of the Arctic wilderness, but even if it does we still have some big challenges to face. Sweeping these under the carpet for the sake of a convenient narrative about a pristine wilderness is not helpful. I have a great affection for the Arctic, the people and the wildlife that lives there. I started this post originally some time ago but failed to finish it as it made me rather depressed to think about, but then I was put in mind of this poem from Seamus Heaney and decided it was worth finishing after all with this piece.

Clearly, the myth of “The North” and “the Arctic” has been with us for some time, but surely we owe it to the Arctic and the peoples who live there to try and see through the “pristinism” and start to fix some of these challenges?

North

BY SEAMUS HEANEY

I returned to a long strand,
the hammered curve of a bay,
and found only the secular
powers of the Atlantic thundering.
I faced the unmagical
invitations of Iceland,
the pathetic colonies
of Greenland, and suddenly
those fabulous raiders,
those lying in Orkney and Dublin
measured against
their long swords rusting,
those in the solid
belly of stone ships,
those hacked and glinting
in the gravel of thawed streams
warning me, lifted again
in violence and epiphany.
The longship’s swimming tongue
was buoyant with hindsight—
it said Thor’s hammer swung
to geography and trade,
thick-witted couplings and revenges,
the hatreds and behind-backs
of the althing, lies and women,
exhaustions nominated peace,
memory incubating the spilled blood.
It said, ‘Lie down
in the word-hoard, burrow
the coil and gleam
of your furrowed brain.
Compose in darkness.
Expect aurora borealis
in the long foray
but no cascade of light.
Keep your eye clear
as the bleb of the icicle,
trust the feel of what nubbed treasure
your hands have known.’

were ocean-deafened voices

Shameless self-promotion…

The annual AGU jamboree starts this weekend, I have never actually attended (I do way too much travelling for work as it is but I would quite like to go one day). However, I and some of my colleagues have contributed to a number of presentations and posters so I thought I’d put a wee list up of those:

https://agu-do.confex.com/agu/fm15/meetingapp.cgi/Paper/82972 this poster presented by Prof. Jason Box on Greenland ice sheet albedo uses my HIRHAM5 simulations.

https://agu.confex.com/agu/fm15/meetingapp.cgi/Paper/59874 this poster presented by Dr Liam Colgan on the life cycle and mass balance implications of crevasses on glaciers relates to this blogpost.

My colleague Christian Rodehacke is presenting some of our work on permafrost modeling (and in particular subsea permafrost on the Siberian shelf and around Greenland) in a presentation on https://agu.confex.com/agu/fm15/meetingapp.cgi/Paper/77877 related to the DEFROST project

Ice2ice work from DMI is represented by a number of posters including this particular highlight on sea ice and surface air temperatures given by my colleague Shuting Yang: https://agu.confex.com/agu/fm15/meetingapp.cgi/Paper/78776

Then there are some good statistical posters based on multimodal ensembles presented by my Research leader Jens Hesselberg Christensen https://agu.confex.com/agu/fm15/meetingapp.cgi/Paper/71989

And while I’m on the subject of ice2ice, did I mention we’re hosting a themed session at the EGU Spring symposium in 2016?

The deadline for abstract submission is 13th January but with Christmas in the way it’s best to start planning your submissions now. I am co-convening the session, titled “Interactions and feedbacks between land ice, sea ice and ocean in the Arctic “ and we’re hoping to invite a couple of keynote speakers, and there may also be an associated social event, so keep watching this space and do consider sending in an abstract to the session!