Why going to Petermann? 2. For Science!

I hope I get to see that! (from ogreenworld.umwblogs.org)

I hope I get to see that! (from ogreenworld.umwblogs.org)

Personally, I want to go to Petermann for the sense of adventure and the amazing views, the ever changing light on the ice, the narwhals piercing through the surface of the water, the polar bears running along our side… Basically, I want what is advertised by polar cruise ships. Except that I find cruises utterly boring. Luckily, Petermann does not only offer the remoteness and crazy wildlife I long for, it is also an incredible site when it comes to science. For in this very location, people interested in the past, the present, and the future of the ocean will be taking measurements during the same expedition! Let me tell you more about these.

The Past Ocean, Alan Mix

Alan Mix from Oregon State University (US) is the chief scientist of our research cruise. That means he is the one who came with the idea of going to Petermann and who gathered enough support to convince NSF to fund it. He and his team are paleoceanographers: they try to understand what the ocean was like thousands of years ago by drilling holes in the ocean floor. They obtain metres of sediment, that is basically mud containing the remnants of dead sea animals, where each layer can be dated relatively easily (using the same methods as archaeologists). Within the layers, the varieties and concentrations of species they find give them indications of what the ocean temperature was at that time.

Benthic foraminifera are used to estimate past ocean temperatures (image Wikipedia commons)

Benthic foraminifera are used to estimate past ocean temperatures (image Wikipedia commons)

During the cruise, they will be performing sediment coring at sea and under the ice shelf (a floating tongue of ice… actually I’ll write about it in 2 weeks!). On land, by looking at where there are rocks and marine sediments, they will also be able to infer ice retreat history and past sea levels. But I’m not sure I fully understand how for the moment, so I’ll explain in more details after I have asked them during the cruise.

The Present Ocean, Andreas Muenchow

Andreas and I will be part of the same subproject during the cruise: the physical oceanography. Andreas Muenchow from the University of Delaware (US) is interested in the whole area around Nares Strait (check his blog here) and is among the lucky few who have already been to Petermann. He is interested in measuring the current properties of the ocean (mostly temperature, salinity and water motion) and understand what is happening to Greenland glaciers. Along with Helen Johnson in Oxford -with whom I work for my 3-year research project- they studied the ocean circulation by Petermann a few years ago and showed that it is not the warming atmosphere but the warm ocean that is melting the glacier.

Onboard Oden, Andreas, Jari, Christina and I will be performing CTD casts to measure the variations of salinity (Conductivity) and Temperature with Depth in Nares Strait and around Petermann. He also wants to measure these properties under the ice tongue, so he shall hitch a helicopter ride to the ice and deploy some sensors down the holes made for another subproject and into the ocean, where no one has ever taken any measurement before.

The Future Ocean, me!

Whether you agree that we are responsible for it or not, I suspect you heard that Greenland is melting. In case you have not:

Ice velocity map from Rignot et al. (2012). Red/magenta = bad news

Ice velocity map from Rignot and Mouginot (2009). Red/magenta = bad news

All around Greenland, the ice stored on land in the Greenland Ice Sheet is falling into the ocean. As soon as it moves from land to the ocean, this ice causes sea level rise (like adding an ice cube into your glass). That is a big problem of course, but I’m interested in a second issue: this ice is made of fresh water, whereas the ocean is salty. And fresh water is lighter than salty water, so it stays at the surface, creating some kind of cap that isolates the rest of the ocean from the atmosphere. My whole project aims at working out whether (and when) this fresh water from Greenland melting will actually stop the ocean deep circulation, severely impacting the European climate.

During the cruise, I will be using the CTD casts to not only understand what the ocean does to the glacier, but also how the glacier responds to that (tracking the fresh water). I will also be deploying some new sensors, developed by Jari at KTH, to continuously measure the properties of the water around Petermann up to a year after the cruise, even through winter when no ship can come.
Well and obviously, I’m hoping to see amazing views and take pretty pictures that I would share with you!


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