I was checking out the latest plots from SG130 yesterday, and I noticed a very interesting feature. The glider is a ways south of Newport, over 100 km offshore, heading northbound. In the last several profiles, in addition to a surface chlorophyll peak (~50 m), there appears a second chlorophyll maximum around 200 meters. Check it out:
The feature shows up in the backscattering data, too, and is not associated with any change in water mass characteristics (temperature or salinity). Is the deep chlorophyll max (DCM) an older surface bloom that has been advected offshore and is now sinking out? It would be neat to look at the glider and satellite data going back in time to see if I could track the origin of this DCM. Time to hit the literature and refresh my memory on the coastal dynamics of summer phytoplankton blooms off of Oregon. Any thoughts from our readers on origins of this feature, and whether or not it is an annual occurrence? I’ve got SG130 data from last summer, too…
Last Monday (7/13/09) we deployed SG130 around NH15 (Newport Hydrographic Line). Conditions were great – almost no wind and very small swells. Captain Mike took us out on the R/V Elakha, OSU’s trusty day-trip vessel. Here you see Justin and I easing the glider off of the fantail, with Mike’s help.
If you want to follow SG130 during it’s mission, follow this link to the Glider Research Group web page. It will be traveling on a path that looks like a capital “E”, where the top of the “E” is the NH line, the middle line is a visit to Heceta Bank, and the bottom is an east-west line near the mouth of the Umpqua River. The last time that SG130 was deployed, we saw some very interesting patterns of sediment resuspension – I am hoping that we see the same patterns again.
Glider Bob decided to spring a leak late Friday (05/22) night. Is there any better timing than that? To make matters worse, Glider Bob was about as far offshore as possible with the prevailing currents pushing him offshore and to the south (cyan track).
Fortunately, Justin was out on the Wecoma and they were able to recover bob early, early Sunday morning without much apparent hassle. We’ll have to talk to Justin to find out for sure. I monitored the recover via glider terminal and the Wecoma’s webcam, while I fed Dashel a bottle around 2am.
Laura left bright and early Tuesday morning on the Elakha to retreive bob from the Wecoma, her report: The transfer went well. Glider and cart were tied to a line and dropped in the water from the Wecoma, and we winched it on board the Elakha. We lucked out with the weather, and as far as I could tell Bob did not hit either of the two ships.
Now we’re waiting to hear from Anatoli just how much water is inside …
At the beginning of April, we had some extended 20 kt bursts of northerly winds off the Oregon shelf,
(image from www.orcoos.org)
and the glider observations show the upwelling response in the coasatal ocean with deep, cool, salty, low oxygen water moving up onto the shelf.
In addition, to the deep water moving up onto the shelf, the fresh water in the surface layer moves off the shelf, and phytoplankton blooms can be seen in the near surface chlorophyll fluorescence measurements. Compare these sections with the clasic winter conditions below.
Here’s the first section from Glider Bob’s Oregon shelf mission. This is our fourth season of making Oregon shelf observations. During the winter, the surface layer is typically well-mixed down to 80 m, the pycnocline slopes downward toward the coast intersecting the bottom near the shelfbreak, and there is a small lense of fresh water very near shore from rain and run-off from small local rivers, and the currents are relatively strong and to the north. In this section, there is also a slight run up the shelf along the bottom of salty dense water, lead by some small scale variability that looks reminiscent of nonlinear internal waves a la the observations by Klymak and Moum (2004).
I’ve been tinkering around with Seaglider data that was collected off of the Oregon coast from September – November 2008. SG130 is equipped with a WET Labs ECO-Puck, which provides us with estimates of Chlorophyll-a concentration (biomass proxy), colored dissolved organic matter (CDOM) fluorescence, and the particulate backscattering coefficient at 660 nm (proxy for particle load, particulate carbon, etc.). The Seaglider also has an oxygen sensor, which will be of great value when seasonal coastal hypoxia sets in again.
At any rate, here is a preliminary plot of data collected along an east/west transect, at apprximately 43.7 N. A large plume of particles being advected off of the shelf is evident in the backscattering data (middle plot on right – ignore the bathymetry for now). More plots to come in the near future!