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).

Microbial Oceanography of the Oxygen Minimum Zone (MOOMZ)

Two OSU Seagliders (sg157 and sg158) were deployed on Friday Mar 6, 2009 off the coast of Iquique, Chile. sg158 was recovered yesterday, but sg157 remains, collecting observations of temperature, salinity, density, currents, chlorophyl, backscatter, CDOM and dissolved oxygen. sg157 will continue to fly a cross-shelf section from about the 200 m isobath to 100 km offshore until July or August.


Currently, sg157 is headed offshore toward 71 W in deep water, making full dives to 1000 m. sg157 is completing dives too quickly, about 180 minutes vs. 330 minutes optimally, which I think is due to the max pitch at +/- 30 degrees. However, the overall flight seems well tuned; I'm getting good low pitch and roll bias numbers.

sg157 is having some altimeter issues, when it comes up onto the slope, getting false returns, and turning around too soon. I'll continue to work on that the next time we come on shore.