WOW! So it has been way longer than I had hoped since I last blogged, and I have still not completed my blog posts for the fieldwork this spring. But in an effort to try to get myself back in to blogging (it takes more time and effort than you might think) and to promote some of the research I am involved with, I thought I'd share a guest post with you today.
Angelika Renner is a senior scientist at the Institute for Marine Research in Tromso, Norway. I first met Angelika in 2010 on a Norwegian Polar Institute (NPI) cruise where we conducted ice thickness measurements using the airborne electromagnetic induction ice thickness sensor (AEM) from our research group. NPI purchased an AEM and so I was training them on how to run the system.
Last year when I was in Norway, Angelika approached me about collaborating on a project while I was there working on my own project, and well I love to collaborate, especially with excellent people like Angelika. Angelika also put me up for several months in her house when I was there (THANK YOU SO MUCH, I really miss fishing!).
Our research (Evidence of Arctic sea ice thinning from direct observations) has now been published and we thought to do a little self promotion and to raise awareness of our results I would cross-post a blog posting Angelika has made on another colleagues blog. Note the guest post here is the same. It is repeated here to try to ensure the widest audience possible (you might be amazed at how many people do not click through web links).
Mirjam's blog is fantastic and it is well worth a read through the archive, seriously, do it. Okay well without further ado here is Angelika's guest post:
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| Photo Credit: Angelika Renner |
Sea ice comes in various shapes, from very
flat, smooth, and thin sheets of newly formed ice to huges ridges several tens
of meters thick. Assessing the thickness of the sea ice cover in the Arctic
remains one of the biggest challenges in sea ice research. Luckily, methods
become more refined, and numbers derived from satellite measurements become
more accurate and reliable, but they don’t cover a long enough period yet to
say much about long-term changes.
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| Photo Credit: Angelika Renner |
Greenland and Svalbard. I learned how to
measure sea ice thickness the hard way: drilling holes. And more holes. And
even more holes. Or the slightly-less-hard way: carry an instrument around that
uses electromagnetic induction to measure ice thickness (since sea ice is much
less salty than sea water and therefore much less conductive). This instrument
is called ”EM31” and we kept joking that the number comes from its weight in
kilograms…. So, using drills and the EM31 we measured on as many ice floes as
we could and given that the cruise went all the way across Fram Strait, that
gave as quite a few datapoints covering quite a large area.
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| Photo Credit: Angelika Renner |
These measurements have been done by the
sea ice group at the Norwegian Polar Institute every summer since 2003, and in
some years also in spring. It takes dedication to build such a time series!
When we could, we also used an airborne version of the EM31, the EM-bird, to do
surveys over larger areas. Now, finally, the results of all these measurement
have been processed, and analysed - and what do we see? The sea ice in Fram
Strait is thinning a lot. Depending which measure you use (nothing about sea
ice thickness is straight forward…), the ice has thinned by more than 50% over
the 10 years from 2003 to 2012!
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| Photo Credit: Angelika Renner |
It’s one thing to know that it has
thinned, but it’s a lot more interesting to find out why. Fram Strait is a
special place: Most of the sea ice that is formed somewhere in the Arctic Ocean
(and doesn’t melt there again) leaves the Arctic through Fram Strait. It is a
very dynamic region with strong currents and winds, which results in a lot of
deformed ice regardless of its age. The extent of the ice cover here is not
necessarily linked to the development of the ice in the Arctic Basin – most
prominent example was the heavy ice year in Fram Strait 2007 whereas this was
up to then the year with the lowest Arctic-wide ice extent in the satellite
era.
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| Photo Credit: Angelika Renner |
We looked in more detail at where the ice
came from and found that this, too, does not correlate with our thickness time
series. While the source region of the ice varied from year to year, it was
continuously thinning – in our opinion a sign that the thinning occurs
Arctic-wide.
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| Photo Credit: Angelika Renner |
A lot of effort went into this paper and
the dataset behind it, and I was very very lucky that I got the opportunity to
participate in several of the cruises, do the data analysis and write the
paper. It’s even more satisfying to see your work published when you know how
much work drilling all those holes was……
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| Photo Credit: Angelika Renner |
, , , , , , , and (2014), Evidence of Arctic sea ice thinning from direct observations, Geophys. Res. Lett., 41, doi:10.1002/2014GL060369.
http://onlinelibrary.wiley.com/doi/10.1002/2014GL060369/abstract
http://onlinelibrary.wiley.com/doi/10.1002/2014GL060369/abstract
