Ocean slicks

[Guest grubmaker]

Hi,

 

From what i understand slicks of calm water are caused when ocean currents diverge. To facilitate a study of marine phylogeography, I need to know how stable slicks are both in time and space, ie are they in a predictable location over geological time and from year to year. Also does anyone have any idea where to find maps covering the s.e asia and s.w pacific regions that detail ocean currents and possible locations of slicks.

 

Being new to this particular field, any advice would be appreciated.

 

Thanks.

[coquina]

From this site:

http://www.stormingmedia.us/47/4704/A470413.html

 

Natural Slicks on the Ocean

Authors: Dietz, Robert S.; Lafond, Eugene C.; NAVY ELECTRONICS LAB SAN DIEGO CA

Abstract: Slicks are smooth glassy streaks or patches on the ocean. Prominent slicks are confined largely to near-shore areas where organic production is high. Experiments and observations are described which show that slicks are contaminate films of organic oil probably derived primarily from diatoms which contain droplets of oil in their cells to assist in flotation and/or as an emergency food supply. Slicks are discernible because of their damping effect on small wavelets. The parallel slicks that develop in light to moderate winds result because the contaminate films pile up at the top of convergenees in the homogeneous wind-stirred layer above the thermocline.

 

 

I don't have a lot of experience with ocean slicks, although I have seen them offshore. I live on the Chesapeake Bay, the largest estuary in the US, and am much more familiar with the slicks seen there.

 

The Bay has both tides and currents, the tide being verticle motion, the current being horizontal. The slicks always do look a little oily - the bay has a large quantity of menhaden, a very oily fish of the herring family. When a school of bluefish or stripped bass is feeding on them, the oil rises to the surface along with the fish scraps, which attracts the gulls. (Fisherman locate schools of large fish by looking for feeding gulls.) However, I have seen plenty of slicks with no birds, so I am sure we have diatoms at work too. Matter of fact, you ought to see a "red tide" caused by dinoflagellates, the Bay looks like tomato soup.

 

Anyway, you see the slicks mostly at slack water, the period when the current is nil as it changes from ebb to flood and vice versa. ("going out" or "coming in"). They are also seen when there is a slight breeze and the wind and the current are going in the same direction. When the wind is against the current, a chop develops and the slick dissipates.

 

Hope this helps.

[Guest grubmaker]

Thanks Sandi thats very helpfull, i'm beginning to build a clearer picture. I'm still a bit unsure about how predictable these slicks are. In Chesapeake Bay are they present in the same general area most of the time? I'm only interested in ocean slicks, so I don't know what kind of difference that makes.

 

Thanks again.

[coquina]

As far as bay currents go, if there is no wind, they move with the current, but the bay currents are different from the ocean ones. In either case, when the winds pick up, they are dispersed.

 

There is a lot on the web about Ocean currents.

Here are some images. Go to the source documents and see if you can narrow it down to where you want to be:

http://images.google.com/images?q=ocean+currents&ie=UTF-8&hl=en&btnG=Google+Search

 

 

Of course, a ship leaking very small amounts of oil and flushing it out with its bilge water would cause the same problem. You have to figure out whether the slick is anthropomorphic or natural.

 

I would think that the natural slicks would be found where it is easiest for diatoms to proliferate. Probably warm, shallow water in the "horse latitudes" and "doldrums", where the winds are very weak.

 

Here's a link that explains those two terms:

http://geography.about.com/library/weekly/aa110200a.htm

 

and here's a picture of global wind patterns:

http://www.erin.utoronto.ca/~w3env100y/env/ENV100/sci/weather_gifs/globalwinds.jpg