Archive for May 12th, 2010

Cook Turns East – Trans-Atlantic II Begins

Wednesday, May 12th, 2010

Yesterday the Thermal Glider Cook reached a latitude of 26 degrees, 30 minutes north, or 26.5 N as it has come to be known. We approached 26.5 N just east of 65 W.  Once we crossed the 26.5 N latitude line, Tod turned Cook east towards the Canaries.  Cook has flown just over 1300 kilometers since leaving St. Thomas on March 21.  Today we start our 2010 summer crossing along a more southerly route than RU27's 2009 crossing.   Only 5,000 kilometers to go till we get to the Canaries.  Timing is perfect.  Today we have a skype call scheduled with our partners in the Canaries on what we can do with this crossing.


Zooming into the region around Cook, we get three views of the eddy field.   First the satellite sea surface temperature (SST).  We are spinning around that clockwise eddy with some of the strongest currents we have seen on this trip pushing us to the northeast.


Next the  satellite sea surface height (SSH).  The altimeters say we have a long ribbon of current heading east as we fly eddy to eddy to eddy.


Last is the Navy HyCOM forecast.  The HyCOM model assimilates the SST and SSH satellite data, uses our knowledge of ocean physics to produce calculate the dynamical balances based on Newtons laws (F=ma), and then uses these balanced these fields to produce a forecast. It gives us a third look at the deep ocean eddy field.


In the last blog I noted the great agreement between the SST and SSH satellite products.  Today I am amazed by how well the HyCOM model (white arrows) agree with the altimeter SSH data (color contours and black arrows).  I know they are supposed to, since the model is assimilating the altimeter data. But as we learned from RU27, that is not necessarily the case.  There is still much to learn in the field of data assimilation, and these Trans-Atlantic flights give us that opportunity.


One thing we will be talking about with our friends in the Canaries is how we use Cook to study heat transport.  Below is the section of temperature derived from Cook on this leg of the journey.  On the x-axis is distance alongtrack. On the y-axis is depth of the glider, with the ocean surface at the top and 1200 meters depth at the bottom. As we head north, the depth of the warm surface layer shallows.  We will be looking at these temperature profiles, and the currents derived from Cook to see which way the warm water is flowing.