I’ve met Angelika on a cruise in the Antarctic Circumpolar Current a long time ago where we worked on an instrument together and created an advent calendar to keep up everybody’s morale during the second month of the cruise before flying home on christmas eve, and we’ve since gone white(ish) water kayaking, hiking in the norwegian mountains, visited each other’s institutes, helped each other out in research and teaching crises (mainly Geli helping me out, to be honest ;-), and we are planning an exciting project together. Angelika and coauthors recently published the paper “Evidence of Arctic sea ice thinning from direct observations“. In today’s post, Angelika writes about how the observations that went into the paper were obtained, and I am excited to share her story – and her amazing photos – with all of you.
There’s been so much liquid water on Mirjam’s blog lately, I was happy to take her invitation for a guest blog to bring back some of the most amazing, interesting, and beautiful variation of sea water: sea ice!
Sea ice comes in various shapes, from very flat, smooth, and thin sheets of newly formed ice to huge 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.
My first proper science cruise in 2005 went to Fram Strait, the region between 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.
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!
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.
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.
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……
Hydrothermal springs that you can visit without a deep-sea submersible.
When teaching about hydrothermal springs, I usually use a video a friend of mine took of hydrothermal vents on the mid-Atlantic ridge on the WHOI submersible Alvin. But being on Iceland now, there is much better material available which students can even go and experience themselves.
I am too chicken to take my camera under water in the Blue Lagoon to film the hot springs, but there are other hot springs all over Iceland that are less scary, for example this one that my friend Astrid found in the middle of a meadow.
And here I even dared take my camera under water.
Granted, this is not quite as impressive as a black smoker or the Blue Lagoon. But the water in the whole little lake was warmer than about 40 degrees Celsius, and the hot spring is sitting randomly in a field. That’s hand-on geothermal heating for you!
Polar bear photos from a cruise last year. Just because.
Imagine you are on a research ship somewhere in the Greenland Sea. You are, as you have been for the previous days and weeks, standing in your lab, titrating oxygen. While you are rinsing bottles, you look out of the lab’s window. Your thoughts wander. You notice a little head swimming somewhere in the distance. You think “oh look, a polar bear!”.
On that cruise we were really lucky – we got to see a couple more polar bears over the next days, and at some point even two at the same time, meeting for the delicious dinner below.
So yes. Is there any job in the world that could be more awesome?
Using a photo from one of my research cruises to explain the formation of wind waves.
Wind waves are (surprise coming up!) waves generated by wind that blows over the ocean’s surface. The size of those waves depends on several factors: The strength of the wind, the length of time the wind has been blowing over the ocean, and the fetch (hence the “fetching” title of this post).
The image above is really useful to talk about this concept. We see the wind direction indicated by the wind vane at the bow of the RRS James Clark Ross. In the lee of the ice floes, the water surface is smooth because it is sheltered from the wind. As the distance from the ice flow, and hence the fetch, increases, waves start forming again. In addition to the formation of waves, you can see how waves are refracted around the ice floe.
I like teaching using photos that I took myself. Not only do they show exactly what I want to talk about, but they also give me the opportunity to share stories, like in this case of how I took that photo when we were first approaching the ice edge in the Greenland Sea and then the next day there was ice everywhere and we saw polar bears. Not only are students entertained and fascinated hearing personal stories of experiences at sea, I think that those stories are also important for helping students form their self-image as an oceanographer, and for motivating them to stick it out through the tougher spots of their studies. Stories also help students remember content, and story telling is a very useful method in the classroom (but more about that in another post).