Dispatch 21: Colored Dissolved Organic Matter in the Arctic     Print

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Mengnan Zhao

October 8, 2015

Our expedition has been going for 3 weeks now and the science activities have been going smoothly as planned. All of the ice buoys have been deployed, and some even have been recovered. Only one mooring is left to be recovered and redeployed in three or four days from now. Water samples are being collected and analyzed in the lab here. The schedule even allows us a chance for some science talks before the daily science meeting.

Today’s talk was given by Scientist Celine Gueguen from Trent University. Celine’s research relates to colored dissolved organic matter (CDOM). CDOM is an optical measure of organic matter in the water that is produced from decaying organic material, and can indicate water origins. We have a CDOM sensor that is part of the CTD/rosette system. As the CTD operator, I am fortunate to be the first person to see the profiles of all water-column parameters (sent back to my computer up the CTD/rosette wire), including temperature, salinity, CDOM, chlorophyll and oxygen. In the Beaufort Gyre, CDOM always reaches a maximum in the Pacific Winter Water layer (around 200 m depth). This water layer contains influence from rivers; water at the shelves sinks to depth in the water column when salty plumes are formed by sea-ice growth or because it is laden with particles that make it heavy. Celine showed the interesting spatial distribution of CDOM from another year (Joint Ocean Ice Studies JOIS, 2011) when the Louis went far north. CDOM in the southern Beaufort Gyre (mostly influenced by Canadian and American rivers) has a smaller concentration than in the northern region (mostly influenced by Russian rivers). The lower concentration in the Beaufort Gyre might be explained by a mixing between river water and basin water. But the high salinity in the northern region implies that Russian river input was not the only contributor to the high CDOM concentration. This would be the next problem that Celine will tackle in her research.

Celine went on her first Arctic Cruise in 2003, and she has obtained data since 2007 that she and her colleagues are currently analyzing. She is also my CTD “buddy” – who I probably spend the most time with on the ship, and who keeps me company with interesting conversations and brings hot drinks on cold nights, making my CTD shack a cozy place where I enjoy working.