Temperature Space & Time Contours
Water temperature is measured as an indicator of mixing and because many biological processes (including fish migrations) respond to temperature changes. The seasonal range of water temperature in the Bay is from about 8 °C (46 °Fahrenheit) to about 23 °C (73 °F).
Figure Caption: The upper panel displays the Delta Outflow Index for 1993-1995. The lower panel shows the changing distribution of water temperature along the USGS Bay transect. Color is proportional to temperature, with darker (red) shadings indicating warm water and lighter (blue) shadings indicating cold water. The vertical axis represents variability in space as we sample from the Sacramento River (top of image), to the Central Bay, and then to the lower South Bay (bottom of image). The horizontal axis represents change over time from 1993 through 1995.
Description of Numbered Regions:
- Water temperature changes with season, and Bay waters are warmest in August when temperatures reach 22-23 ° C (or about 73 °F) .
- Bay waters are coldest in December and January, reaching minimum temperature of about 8 °C (or 46 °F).
- In summer, the water is warmer in the Sacramento River than in the Central Bay (Bay Bridge). This shows the effect of mixing between warmer Bay waters and colder waters from the Pacific Ocean.
- Sometimes we see sharp temperature gradients, like this one near Hunter's Point. These gradients suggest regions of slow horizontal mixing. In this case a bump in the sea floor, the San Bruno Shoal, acts to slow mixing between the South Bay and Central Bay, allowing the South Bay waters to warm up faster than the Central Bay waters which are close to the colder Pacific Ocean.
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U.S. Department of the Interior |
U.S. Geological Survey
