>: "International Cooperation on Investigation and Research of Manne Natural Resource and Environment- SHELF-SLOPE PHYSICAL/BIOLOGICAL RESPONSE TO MONSOONAL WIND FORCING AND RIVERINE INFLOW- 4D SAMPLING WITH TOWED PROFILERS AND AUTONOMOUS GLIDERS OFF VIETNAM Craig M Lee' Burton JonesS Luc RainviIle^ Emmanuel Boss'', 1-Applied Physics Laboratory, University of Washington, Seattle, WA, USA 2-University of Southern California, Los Angeles, CA, USA 3-Applied Physics Laboratory, University of Washington, Seattle, WA, USA 4-University of Maine, Orono, ME, USA Abstract: =., The coastal circulation around Vietnam is strongly affected by modulations of windforcing and riverine inpul primarily associated with the seasonal change ofmonsoonal atmospheric forcing The continental coastal and shelf topography constrain the response of the ensuing circulation, both near the coast in the interior of the Vietnamese East Sea The biogeochemislry of coastal and offshore waters, as observed in the ocean color, is tightly coupled to the physical forcing al all scales Here we present concepts for an observational study focused on characterizing the tight coupling between physics and biogeochemislry at two opposite phases of the monsoon A combination of ship-based and autonomous surveys of physical and optical properties could sample processes associated with stratification, sediment resuspension, biological patchiness and adaptation, all of which can be related to properties that can be observed using satellite remote sensing Objectives This observational program is designed to understand: The physical response to the monsoon The resulting effect of the physical fields on the coastal biogeochemistry as reflected in optical properties The contribution of dissolved and particulate matter to in-water optical properties and their effect on ocean color remote sensing Relationship between the surface expressions of three-dimensional ocean processes and the interior processes Large riverine freshwater inflows, coupled with seasonally reversing monsoonal wind forcing and complex topography govern dynamics and biological variability over the shelf and slope surrounding Vietnam Large scale wind-forced dynamics, dominated by the monsoons, explain the underiying basin-scale circulation in the Vietnamese East Sea (Bayler and Liu 2008), though processes acting at shorter spatial and temporal scales, such as riverine buoyancy input, topographic effects, and enhanced mixing driven by local and remote internal tides will modulate response to broad monsoonal wind patterns Moreover, the seasonal phasing of riverine inflows and monsoonal winds results in tight coupling between physical Craig M L« — ^ Hoi thao khoa hoc - Hop tac Quic ti dieu tra, nghien cuu tai nguygn va mfli truang biin and biological processes along the Vietnamese coast The winter (Northeast) monsoon (Figure la) imposes strong northeasterly winds over the South China Sea, shifting rapidly in spring to the slightly weaker southwesterly winds of the summer monsoon The combination of southward (downwelling-favorable) alongshore wind forcing and the predominant cyclonic circulation produces an intense (speeds greater than I m/s; (Tseng 2006)), southflowing coastal jet that extends from the continental slope south of China to the eastern seaboard of Vietnam and onto the broad shelf near the Mekong delta Wlntflr (northeast) monsoon , ^ Summer tsouthwestl monsoon |t»aw™[ffBtopHnWon Intloctiaia pGfiinsua WIND^ f \ \ J / cbntc cir IdilofTnaland) phytc^anUon Non masieitf w n i s s m lorUwoDasulleL Fig Schematic of the East Sea circulation and phytoplankton blooms during (a) winter and (b) summer monsoons (adapted from Tang et al., 2006) The solid gray area Indicates the region dominated by the Mel