MOOMZ SG157 - Line 5

Here is a plot of the upper 400 meters of the latest seaglider section off of Iquique (27 March - 07 April 2009, onshore to offshore track). On a hunch I plotted salinity contour lines on top of the oxygen (upper right) and backscattering (middle right) data. It seems that there is tight coupling between salinity and both O2 and bb. Before seeing these data, I would have guessed that variability in the deep oxycline would be driven by intrusions of water masses with different density and oxygen characteristics. Likewise with the bottom boundary of the intermediate depth scattering maximum. However, given what we see here, the story seems to be a bit more interesting than that! Why would salinity be more influential than density in regulating these distributions?

MOOMZ 5 - our first complete section

Full profile (0-1000m) below \/, surface to 400 meters above /\

Seaglider 157 recently completed it's first complete onshore to offshore section, and the data are fantastic! As you saw in the profiles, the oxycline is consistently very near the surface, ranging from 30 to 75 meters depth. Becasue the oxycline is so shallow, we often observe a second chlorophyll peak within hypoxic waters (oxygen below 20 umol/kg or 1 mL/L). We also see consistently elevated backscattering signals throughout the OMZ, from the oxycline to about 300 meters depth. We hypothesize that this signal is at least partially derived (if not mostly) from enhanced microbial activity in the OMZ, and look forward to ship-based sampling to test this idea. We have observed these same features in data from Apex profiling floats that were released in the area last March (Whitmire et. al., in prep.; link to data, link to plot).