Western Channel Observatory Blog

After several years of the pressure readings not being reliable (in terms of a power supply) the readings should now be much more consistent (i.e. not suddenly dropping to 600 mb!).

Tim

Following some extensive detective work by Peter Walker and myself we have now managed to get the met station up and running again. There was a communications problem with the serial to ethernet box in the plant room which had somehow hung. The pressure readings (690mb!) look somewhat dubious - but might be able to rectify that later.

The good news is that the data loss is much less severe than I first thought. There is around 2 weeks of data that we didn’t realise we had (which will be processed as soon as possible). The data missing period is between 3 - 14 November.

Tim

After the windy weather last week and the large swell we weren’t expecting the vis to be up to much this weekend.  However, although it was not crystal clear we had about 8-9m on the Persier a wreck in Bigbury Bay and the same again on Tinker Shoal just south of Plymouth breakwater.  There was what appeared to be a halocline (or perhaps thermocline, but I couldn’t feel any temperature difference) at Tinker Shoal.  Water is starting to cool down , it was about 15 degrees.

Young Fish Trawl being deployed

Eddystone

Sample from WP2 net

filtration rig

There has been some cracking vis during the last week of September!

27th Sept Start Point 16 m deep, 15m vis.  Short bits of snot (approx 1 cm long) thoughout the water column.  Water temp 15 degrees C.

28th Sept Eddystone Lighthouse.  15 m vis.  Not snotty.

30th Sept Brixham Breakwater beach 5 m vis.

Here’s a quick update on my post last week. The stratification in the Western Channel has continued to break down, indicated by the stratification surface front receding towards the shelf. The resulting increase in nutrients (and fine weather) has established a larger bloom, probably the dinoflagellate Karenia mikimotoi (can anyone confirm?) though only in moderate concentration. This type of bloom occurs here most years, though normally earlier - in August rather than late September: is this due to the lousy summer?

Aqua-MODIS chlorophyll-a (OC5) on 27 Sep. 2008 1305 UTC

Near true-colour scene on 27 Sep. 2008 1305 UTC, darker green indicates higher chl-a, brighter water indicates suspended sediment

Hi folks,

I have now georss enabled this blog. In plain speak that means that articles can now be geographically encoded with a latitude and longitude. I have geo-coded this post with the position of L4 as an example.

Martyn

After 6 weeks, the L4 mooring legs have now been made safe and marked with surface buoys (marking the western and eastern ends).  We plan to get some remedial welding work done to both buoys and the L4 data buoy back out before the onset of the winter - probably without instruments to test the strength of the mooring.

After 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.

This 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.

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.

During this week the Quest crew have managed to retrieve both parts of the E1 mooring. The site is now clear and the mooring ropes returned to shore.

We now need to visit the L4 moorings.