23rd Sep, 2008

Autumn phytoplankton bloom in Western Channel

Aqua-MODIS Chlorophyll-a scene on 21 Sep. 2008 at 1348 UTC, mg m^-3, OC5 algorithmAfter a few sunny days (Indian Summer?) there’s an interesting ribbon of increased chlorophyll-a concentration along the front separating the seasonally-stratified shelf sea from the tidally-mixed Channel. The ribbon stretches across the Channel from Brittany towards Plymouth, and there is another bloom south of Ireland.

Here is a chlorophyll-a map acquired from the Aqua-MODIS satellite sensor on 21 Sep. 2008. This may be the start of an Autumn bloom, and will be one to keep an eye on. Click here to view near-real time satellite data for this region.

Aqua-MODIS enhanced false-colour scene on 20 Sep. 2008 at 1305 UTCThis is a corresponding enhanced false-colour ocean colour view, showing pure water as blue, phytoplankton as green/brown/red, and suspended sediment as white or yellow. The bloom is not actually red, it would look more greenish brown.

Note the dramatic difference in sediment concentration between the stratified and mixed water.

 

AVHRR thermal ocean front map from 15-21 Sep. 2008, Composite front map method (Miller, in press for J. Mar. Sys)This is a thermal ocean front map, automatically generated from all cloud-free AVHRR sea-surface temperature data from 15 to 21 Sep. 2008. It clearly shows the ocean front separating the warmer stratified shelf water and colder mixed water.

Over the last few days this front has intensified and moved northwest. This is allowing nutrients from deeper in the water column (below the thermocline) to reach the surface and increase the production of phytoplankton.

Responses

This is a really excellent set of images – thanks Pete.  It ties up well with the in situ measurements over the past couple of weeks (nutrients and the CTD profiles currently available).

Tim

[…] a quick update on my post last week. The stratification in the Western Channel has continued to break down,

[…] the MODIS Aqua sensor. The bloom is located further west than the one observed in late September (1,2) last year. Near real time data for this area can be viewed on our Multiview […]

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