Arctic melting: The science behind the ice

Posted by sara_a - 12 September 2012 at 11:44am - Comments
Dr Julienne Stroeve, a research scientist at the US National Snow and Ice Data C
All rights reserved. Credit: Greenpeace
Thinner ice means more melting

Two of the scientists travelling with Greenpeace on the Arctic Sunrise are Dr Julienne Stroeve, a research scientist at the US National Snow and Ice Data Centre (NSIDC), and Nick Toberg, an ice scientist at Cambridge University. I asked them what research they would be able to do on the ice, and for some insight into why Arctic sea ice is so important, and what impact the melting would have on our climate.

What will you doing on the ice?

Julienne: I’ll be measuring ice thickness – it’s a more important measure than ice extent as it tells you about volume (total) loss. I can measure thickness in different spots by drilling with a hand augur, which can go two metres deep. I also hope to look at snow thickness, whether there are melt pools on the ice and whether they are frozen. As the ship is travelling we will also measure the ocean temperatures.

Nick: We will test impact of ocean waves as they hit the ice edge, using buoys fitted with accelerometers. This will fill in the missing physics of how the strength of the waves adds to the ice breaking up and melting. Broken ice reflects sunlight less well as the sun’s rays are
absorbed into the ocean beneath. The lack of ice creates even stronger waves which break the ice up more the following year.

What is happening to the sea ice this year?

Julienne: This year the ice edge has pulled back significantly – in some places by hundreds of miles. By June, the ice edge had pulled back to where it would usually be at the end of September (just after the minimum) in some places. It reached its lowest point ever – 3.51 million sq. km and is still melting.

Why is this year so different, has it been particularly warm, like in 2007 (when the previous record was set)?

Julienne: I’m quite amazed by the level of melting this year, as we knew the ice was getting thinner but hadn’t realised by how much. This year the weather was not particularly warm or conducive to melting. So it must be because the ice is very thin. As more thick ice melts, it is being replaced with first year ice which is much thinner, so the fast melting will continue every year now. I really think, if this year we’d had the weather patterns of 2007, the sea ice extent would be below 3 million sq. km.

Nick: In 2007 the weather conditions were right for the ice to shrink. In 2011 there were no unusual weather conditions but the ice came close to beating the 2007 minimum. Due to previous melting, the sun’s rays which used to be reflected by the ice, have been absorbed into the oceans, heating up them up. So once this pre-conditioning is there, the long-term trend is towards increased melting. We’ll see ice free summers in all of our lifetimes.

What are the different functions of ice thickness (volume), and ice extent (surface area)?

Julienne: Well, ice extent is important for reflecting the sun’s rays and keeping the atmosphere cool. But if we lose ice volume, the ice becomes very thin and melts more easily. The decrease in thickness is why we are losing so much surface area of the ice. Thickness also affects polar bears as they cannot hunt on thin ice, they will just fall through.

As surface area continues to shrink how is melting affected?

Julienne: The heat which was previously reflected by the ice is now mostly absorbed by the ocean; but in autumn when the ice begins to refreeze the heat is absorbed by atmosphere, leading to more clouds and greater moisture in the atmosphere. More clouds in autumn and winter actually keep the atmosphere even warmer. This pushes heat back down to the ocean’s surface, accelerating the ice loss.

How do we know the melting is caused by human activities?

Julienne: We know the heating is caused by humans, by measuring the carbon in the atmosphere and tracing where the carbon is coming from; there is a difference between natural carbon in the atmosphere and carbon from burning fossil fuels. It is hard to differentiate between natural warming and that caused by human activity. But when you create models and leave out the human caused CO2 levels in the atmosphere, none of the models show this level of warming. Based on new climate models, a paper I have just published in Geophysical Research Letters [August 2012] estimates that 60% of the rate of decline in summer sea ice extent is due to human activities.

Nick: Arctic sea ice extent has gone down 10% per decade since the 1970s. The Arctic has had very substantial ice cover for the last 13 million years (shown by recent research on sediments). When it has reduced as a result of natural cycles it has done so over tens ofthousands of years. What is significant now is the speed with which sea ice cover is reducing.

What is the long term picture?

Nick: If the remaining 4 million sq. km of sea ice disappear in summer, that would equal adding 20 years’ worth of CO2 to the atmosphere (at today’s levels of CO2 emissions). In the 1970s we had 8 million sq. km of summer sea ice, so it has halved in the last 30 years.

Julienne: If we keep warming the atmosphere, the Arctic could be ice free in the summer by 2030. While natural climate variability could increase ice levels for a few years, it is on a downward long term trend. We have entered a new climate state in the Arctic – a new year round warmer era.

This year is significant – we’re on the extreme end of current climate models. Our observation is that sea ice decline is happening much faster than most of the new IPCC models.

What are the impacts on areas of the world beyond the Arctic?

Nick: The ice is a big cooling system and the earth’s weather patterns depend on it. There will not be the same dispersion of cold and heat - for example, warm water currents will not move past Britain any more – making it less temperate. Britain is actually at the same latitude as Siberia and is made warmer by the North Atlantic current.

Julienne: The Arctic drives Northern Hemisphere weather patterns. Open water absorbs heat, which is transferred into the atmosphere, making the atmosphere warmer. This alters the movement of air, which changes the jet stream. The wind speed becomes slower, extreme weather conditions stay longer, producing drought conditions in the US for example. It is very early to be sure of this, but it does make physical sense.

How do you think the world will respond?

Nick: It’s disturbing that we have changed the face of the planet in a way we can visually see. But people won’t really change until it affects them on a day to day level.

Julienne: I hope that this year’s sea ice loss will have an impact on the US government and change thinking.

There may already be nothing we can do. Not that this should be an excuse for not trying, but liquid H2O stores an enormous amount of energy; you've got to remove all that energy to turn it back into ice. Where is all that heat going to go? Even if you could re-freeze what we've lost, that's not enough- you have to remove all that energy from the planet, or we still have to deal with it somewhere. Any thoughts about how we can concentrate and export energy on a global scale?

There may already be nothing we can do. Not that this should be an excuse for not trying, but liquid H2O stores an enormous amount of energy; you've got to remove all that energy to turn it back into ice. Where is all that heat going to go? Even if you could re-freeze what we've lost, that's not enough- you have to remove all that energy from the planet, or we still have to deal with it somewhere. Any thoughts about how we can concentrate and export energy on a global scale?

Plus which, you've got to correct both the cause and source of the problem; remove the huge bank of greenhouse gases from the atmosphere, and stop producing more.

Plus which, you've got to correct both the cause and source of the problem; remove the huge bank of greenhouse gases from the atmosphere, and stop producing more.

Icenine, "There may already be nothing we can do".

Not so. We do need a new energy regime planetwide. That has to be solar, both PV & thermal (the sun supplies, in one hour, as much as all the rest of the energy we produce/ use/ waste in one year). Wind is also a solar derived resource. 

Even though there must be a high dgree of latency in the system (most obviously in things like ice melt), yet the situation is still recoverable. When you ask, "Where is all that heat going to go? ", well, if/ when we stop adding to the problem, by still burning carbon (esp. the fossil form of it), then that heat will dissipate to space. 

We (i.e. anyone aware of the problems) need to persuade electorates and policy makers of these fundamentals of energy, which are quite different from what they (wrongly) assume are fundamental. Whether oil is approaching exhaustion of fields (or not) is unimportant. The same for Fracked NSG, for all fossil fuels and for nuclear. We can survive, and see a gradual (100- 200 years?) repair of our ecosystems, IF we stop burning carbon, anytime soon.

 

 

Given  the  seriousness  of  the  latest  reports  on  the  rapid  depletion  of  the  arctic  ice,  should  we  start  thinking  about  campaigning  for  a ' high  tech'  solution  to  save  the  remaining  ice?  I  know  this  sounds  like  science  fiction,  but  the  consequences  for  the  world  of  the  disappearence  of  the  ice-cap  are  so  catastropic,  that  it  might  be  worth  a  try.  The  remaining  ice  cover  appears  to  be  about  three  and  a  half  million  square  km.,  so  it  would  have  to  be  a  massive  international  effort, ( very  difficult  in  itself )  and  all  countries  would  have  to  agree  etc.  Two  americian  scientists   Lowel  Wood  in  the  past  proposed  a  geoengineering  space  mirror  and  Rogel  Angel  proposed  discs  in  space,  but  there  must  be  other  ideas  out  there.  How  about  covering  the  remaining  ice  in  a  reflective  sheet?  What  do  other  people  think?

Nice way of explaining this subject, this science behind the ice line of content is very interesting.
Great article, thanks for sharing, keep up the good work !

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