A ten-year time series from Monterey Bay,
California: Seasonal, interannual and long-term patterns
L O N G -T E R M T R E N D S
5. Long term trends for upwelling index, winds and currents, SST, temperature at 60 m, sea
surface salinity, sigma-t, surface nitrate, nitrate at 60 m, surface chlorophyll,
integrated primary production, centric diatoms, pennate diatoms, dinoflagellates, and
small phytoplankton (less than 5 µm) for the study period. The trends suggest increasing
equatorward winds during the spring and increasing poleward winds during the winter. The
equatorward surface currents are increasing in strength and the poleward undercurrent is
as well. SST is increasing at a rate of 7.9°C per 100 years, salinity, density,
subsurface nitrate, chlorophyll, primary production, and centric diatoms are all
decreasing. Dinoflagellates and the small phytoplankton are increasing.
Winds and currents
The winds at 46012 do not show any long-term trend. However, when
trends are analyzed by season there are increasing equatorward winds during the winter
(more and stronger storms) and increasing poleward winds during the spring. The surface
currents are increasing equatorward and the deeper currents are increasing poleward (Fig
Temperature and salinity
Temperature at the surface and 60-meters increased over the period of
study. SST increased at the rate of 7.9°C per 100 years. Salinity and density have both
decreased (Fig 5).
Nitrate at the surface has an increasing trend and nitrate subsurface
has a decreasing trend (Fig 5).
Chlorophyll and primary production
Chlorophyll and primary production are decreasing over the period of
study. Chlorophyll is decreasing at a faster rate than production (Fig 5), as the decrease
in this property has been tempered by an increase in the productivity index (production
normalized to chlorophyll).
Phytoplankton taxonomic groups
Centric and pennate diatom biomass have decreased over the period of
study. Dinoflagellates and the small phytoplankton have increased (Fig 5).