|The circulation of Monterey Bay and related processes|
Breaker, L.C.; Broenkow, W.W. (1994). The circulation of Monterey Bay and related processes. Oceanogr. Mar. Biol. Ann. Rev. 32: 1-64
In: Oceanography and Marine Biology: An Annual Review. Aberdeen University Press/Allen & Unwin: London. ISSN 0078-3218, more
Circulation; INE, USA, California, Monterey Bay [Marine Regions]; Marine
|Authors|| || Top |
- Breaker, L.C.
- Broenkow, W.W.
The surface circulation of Monterey Bay is relatively weak. Early attempts to ascertain this circulation are initially summarized. Recent results indicate that the surface circulation is predominantly northward (i.e. cyclonic) with speeds usually in the range of 5 to 20cm/sec; however, major reversals in flow direction do occur. The influx of fresh water, although relatively small, plus seasonal heating and residual tidal influence may all contribute to northward flow inside the Bay. During spring and summer, cooler waters which often occur across the entrance of Monterey Bay are most likely due to both local and advective processes. Temperatures at intermediate depths in Monterey Bay (~25 to ~150m) suggest that geostrophic flow within the thermocline may be opposite to that at the surface (i.e.anticyclonic). However, reversals in flow direction at depth from anticyclonic to cyclonic may occur when offshore flow in the California Undercurrent is weak. Seasonal changes in the deep circulation in Monterey Bay may be related to seasonal changes in the strength of the California Undercurrent. The deep flow in Monterey Submarine Canyon is vigorous (up to ~100 cm/sec) and frequently upcanyon, and oscillations in current speed and direction are often supertidal (i.e. of higher frequency). Nonlinear effects associated with very high amplitude internal waves may contribute to onshore flow within the Canyon. Supertidal frequency oscillations may also arise from nonlinear effects, and superinertial frequency oscillations may occur due to the narrowness of Monterey Submarine Canyon.Residence times for bay waters estimated from sea surface temperatures (SSTS) inside and outside the Bay range from 5 to 12 days. Mean internal Rossby radii of deformation range from 10 km over Monterey Submarine Canyon to about 1 km around the periphery of the Bay, reflecting the strong influence of bottom depth. A scale analysis suggests that several processes, in addition to those usually indicated for the deep ocean may be important in the Monterey Bay coastal region.Coastal upwelling through advection from outside the Bay, open ocean upwelling through positive wind stress curl and deep upwelling in Monterey Submarine Canyon may all contribute to the upwelled waters found in Monterey Bay. These waters, which are enriched through this unique combination of upwelling-related processes, most likely account for the very high biological productivity that characterizes this region. A number of additional processes affect the circulation of Monterey Bay including winds, internal waves, mixing, tides, local heating and river discharge, eddies, oceanic fronts, spring transition events, 40-50 day oscillations and El Niño episodes. These processes are described. The circulation in Monterey Bay is also strongly influenced by the circulation offshore. The circulation offshore is complex, consisting of eddies, interleaving alongshore flows involving the interaction of different water masses, and offshore jets. This complexity may be due, in part, to the presence of the Bay itself and the Canyon. Finally, a conceptual model of bay circulation is presented that reflects a synthesis of the available observations and theory. Because of the importance of Monterey Submarine Canyon in influencing the circulation within Monterey Bay, 16 other bay/canyon systems are identified globally where canyons may influence the local circulation.