The Seascapes

The Seascapes

Tuesday, June 22, 2010

Recent Ocean Temperatures in the Seascapes

In this and posts the rest of this week I want prepare for our upcoming plankton sampling cruises by analyzing the recent history of the environmental factors likely to determine which fish larvae will be in the ocean next week, how healthy they may be, and where they may have come from and where they are going to as they pass through our New York and New Jersey Seascapes.  Those important factors include wind, freshwater  discharge from the Hudson-Raritan estuary into the ocean, tides and water temperatures.

The trend in water temperatures at the coastguard station Sandy Hook (NOAA Station SDHN4) over the last 30 or so days (in blue) as well as average daily values for 2005 -2009 (green) are shown in the figure below. Temperatures in early June this year and the last few days are warmer than than they have been in June during the recent past.

The figure below shows a 3 day rolling average sea surface temperature (SST) image of the Northwest Atlantic that Matt Oliver from U Delaware makes available. The SSTs are in the 20s which is quite seems quite warm for this time of year, but I have yet to find a good comparison with June SSTs in earlier years (but see here). The image in the right panel of the plot is really interesting.  It shows allot of variability in temperatures in the vicinity of the southern flank of the Hudson Shelf Valley. This seems to be a consistent feature in these maps and indicates where strong temperature fronts may form and wiggle around allot. The same spatial pattern is often visible in surface currents measured with HF radar when winds blow out of the south or southwest. There are all sorts of interesting physical and biological phenomena associated with the Hudson Shelf Valley in this area.  It seems to be an important faunal boundary. We've measured differences in the bottom fish and invertebrates, as well as ichthyplankton in samples we've collected in the seascapes off Long Island and New Jersey over the past two years.   Even though the Long Island seascape is only about 20 km north and east of the New Jersey site it had more species common to New England.

Finally this is a finer scale SST image showing warmer water overlying both seascapes. Usually the warm water is saltier over the Long Island Seascape which often receives water from the east.  The water over the New Jersey site is often warm and fresh at the surface because that seascape bathed in  water from the Hudson-Raritan river estuarine plume. Warm temperatures, up to a point, should increase the growth and decrease the duration of the larval stages of fish.  Warm temperatures can also lead to earlier spawning by adults.

Differences in source waters for the two seascapes could result in differences in species making up the "larval pools" for the two areas as well as differences in predator and prey communities they encounter. These are the kinds of "supply side ecology" questions we are trying to begin to answer with our cruises next week.

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