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Coastal Mixing and Optics (CMO)

Ocean Physics Laboratory

CMO Data Highlights

During the first deployment, UCSB's Ocean Physics Laboratory was able to capture the physical and optical effects of Hurricane Edouard and Hurricane Hortense. The eye of Hurricane Edouard passed within roughly 110 km of our mooring on September 1, 1996 (see figures below), and soon after, Hurricane Hortense passed within 350 km of our mooring on September 13, 1996.

Edouard Edouard
Left: Track of Hurricane Edouard. Right: AVHRR image of Hurricane Edouard on September 1, 1999.
Note: UCSB mooring is at 40.5oN, 70.5oW
(Both images are courtesy of JHU/APL)

The advantage of taking high-frequency interdisciplinary time-series measurements is apparent in the plots shown below. With the passage of Edouard, the mixed layer deepened rapidly with temperature differences from the top (13.5 m) to bottom (68 m) decreasing from 12oC to about 2oC (see figure below). Sediment resuspension was dramatic as well and is easily seen in all optical data, including the ac-9 data (see figure below). The resuspension event is evident from 68 m clear up to the 37 m depth. Surprisingly, Hortense's passage resulted in significant sediment resuspension despite its relatively great distance from the mooring site.

ac9 Time-series of wind speed (courtesy of Steve Lentz and Steve Anderson (WHOI), temperature at four depths, absorption and attenuation coefficients measured by the WET Labs, Inc. ac-9 (68 m) showing the effects of Hurricanes Edouard and Hortense. (Click on image for full size.)

Highlights from the second CMO deployment include the passage of a northeasterly storm ("noreaster") on October 20, 1996 (Julian Day 294), and a deep warm water advection event that resulted in a temperature increase of approximately 4.5^oC at a depth of 68 m on December 15, 1996 (Julian Day 350) lasting only one day. The left figure below shows physical data for the entire second deployment (JD 270 - JD 4). WETStar fluorescence data at all depths is shown in the right figure below. Note the increase in fluorescence following the passage of the noreaster, and the decrease in fluorescence at 50 and 68 m depths with the warm water advection event.

Deployment2 Full time-series plot of physical data from CMO Deployment 2. (Click on image for full size.)
Deployment2 Full time-series plot of WETStar fluorescence data from CMO Deployment 2. (Click on image for full size.)

Highlights from the third deployment include advection of warm, salty, slightly stratified water from the persistent, yet spatially varying shelf/slope front just offshore from the CMO mooring site (seen in the temperature figures below).

The fourth deployment featured the spring bloom and several storms.

Below are two figures of temperature for all four of the CMO deployments. Notice the seasonal cycle in the temperature, with stratified waters in the summer months (July through October), then deep mixing through December, then thermally inverted water in the winter months (December through April), a re-mixing of the water column in spring, and finally, re-stratification in the summer months.

All temps Time-series plot of temperature for CMO Deployments 1, 2, 3, and 4, illustrating the seasonal cycle. (Click on image for full size.)
Temp Contour Contour plot of temperature for CMO Deployments 1, 2, 3, and 4. The black line represents the mixed layer depth, calculated using a 1oC temperature criterion). SEACAT, TPOD, MDR, and MTR temperatures for Deployment 1 courtesy of Murray Levine and Tim Boyd of OSU. (Click on image for full size.)

All OPL CMO mooring data are available on CD-ROM. Please contact Grace Chang if you are interested in having one mailed to you.