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Four Moorings Redeployed, and O Canada!

DavisStrait09_Knorr_16Oct2009_BI4_6_sm We did CTDs through the night in 35+knot winds; my watch ended at 7 in the morning, after which I promptly went to sleep, so I could get up a few hours later when the daywatch guys had finished the last of the CTD stations, transited north, and deployed the first mooring near Baffin Island. There was an iceberg north of us, near the horizon (the ship's mates like to keep those icebergs as far away as possible), and visibility was fairly poor. There was an awesome jagged black promontory that appeared to the south of us for a few minutes, but by the time I'd fetched my camera, the fog had obscured it again.

DavisStrait09_Knorr_16Oct2009_C1_1_sm The moorings are essentially a series of instruments attached to kevlar line and some small lengths of steel chain (typically painted to avoid corrosion). This is a small frame with an ADCP for measuring current speed and direction at a variety of distances, an external battery and logger, and an SBE37 microcat for measuring temperature and salinity.

DavisStrait09_Knorr_16Oct2009_C1_3_sm Another instrument commonly deployed on these moorings are Aanderaa RCM-8s, current meters made back in the '80s. Nowhere near as high-tech as the ADCPs, they measure velocity and direction of horizontal currents at one depth -- simple and sturdy still goes a long way in observational oceanography.

So why are we deploying these things? There are two interesting currents here at the base of Davis Strait -- warm, salty Atlantic water flows northward along the western coast of Greenland, and cold, fresher Arctic water flows southward the eastern coast of northern Canada. There's some recirculation that happens to differing amounts during the year and it would be good to know what affects the strength of that recirculation; there's the question of whether there are any trends in the overall net southward flow -- is it warming? is there more or less ice or ice melt coming through? Combined with the analyses that will be done on the water samples taken during all those CTD casts, there should be a pretty good story about the water masses that flow through Davis Strait, a/k/a the Arctic Gateway to the Atlantic.

PS: The grad student working on the physical oceanography side of this is B. Curry, not me. I just got lucky this year with timing and got to be the one on the cruise.

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