Science Results : Daily Update

Daily Update | Current SEA Research

July 7, 2010

By Giora Proskurowski

We've got a busy station a little early tonight, so this update will be short. I plotted up our cruise track with wind arrows on it, the warm colors representing faster wind speeds, the length of the arrow scaled to the wind speed, and the direction of the arrow indicating the direction the wind is blowing.

I like this figure because first and foremost it shows the unbelievably favorable weather we had for this cruise track. You can see that as we left Bermuda the winds were moderate and then light, and primarily from the north – perfect for sailing east. Winds then shifted to the south, and a low-pressure system moved through (when we were at about 32°N x 54°W) with associated winds from the southwest – also a favorable breeze for us.

Winds moderated and continued from the south for almost another 600 miles of easterward travel. Then, miraculously, as we turned south to start the mapping portion of the cruise, the wind started to blow from the east, which would have made sailing to the east difficult, but made sailing south, north and west doable. And since then we've had favorable easterly wind, blowing around 15 knots until just the past couple of days.

Secondly, by comparing this figure to the figure of plastics in our neuston net you can start to see some patterns. The strong winds during our zig-zags in the south correspond with smaller amounts of plastic in our tows, while the light and variable winds during our initial easterly leg correspond with large numbers of plastic. The big haul occurred at the top right corner of our track, where the winds shifted from south to east. So far this result is in line with our hypothesis that wind-driven mixing will decrease the amount of plastic in the surface, and thus the amount of plastic we sample in our nets is just a fraction of what is actually in the upper ocean.

Now, back to our station where we will deploy a CTD, use a McLane pump to filter a large volume of water through a 10 micron filter to look for very small plastic pieces, and, of course, we will do a neuston tow.

--------  

For more from sea, listen to an interview with Chief Scientist Giora Proskurowski on the July 2, 2010 Science Update podcast, produced by AAAS.