Woods Hole Oceanographic Institution

About: Woods Hole Oceanographic Institution is a nonprofit organization based out in Falmouth, Massachusetts, United States. It is known for research contribution in the topics: Population & Mantle (geology). The organization has 5685 authors who have published 18396 publications receiving 1202050 citations. The organization is also known as: WHOI.

Hydrography of the Labrador Sea during Active Convection

Abstract: The hydrographic structure of the Labrador Sea during wintertime convection is described. The cruise, part of the Deep Convection Experiment, took place in February‐March 1997 amidst an extended period of strong forcing in an otherwise moderate winter. Because the water column was preconditioned by previous strong winters, the limited forcing was enough to cause convection to approximately 1500 m. The change in heat storage along a transbasin section, relative to an occupation done the previous October, gives an average heat loss that is consistent with calibrated National Centers for Environmental Prediction surface heat fluxes over that time period (; 200 Wm 22). Deep overturning was observed both seaward of the western continental slope (which was expected), as well as within the western boundary current itself—something that had not been directly observed previously. These two geographical regions, separated by roughly the 3000-m isobath, produce separate water mass products. The offshore water mass is the familiar cold/fresh/dense classical Labrador Sea Water (LSW). The boundary current water mass is a somewhat warmer, saltier, lighter vintage of classical LSW (though in the far field it would be difficult to distinguish these products). The offshore product was formed within the cyclonic recirculating gyre measured by Lavender et al. in a region that is limited to the north, most likely by an eddy flux of buoyant water from the eastern boundary current. The velocity measurements taken during the cruise provide a transport estimate of the boundary current ‘‘throughput’’ and offshore ‘‘recirculation.’’ Finally, the overall trends in stratification of the observed mixed layers are described.

Trajectories of sinking particles in the Sargasso Sea: modeling of statistical funnels above deep-ocean sediment traps

Abstract: Characteristics of statistical funnels above moored deep-ocean sediment traps at the Oceanic Flux Program (OFP) site in the Sargasso Sea were determined by Lagrangian analysis of particles sinking through a realistic horizontal velocity field. Stochastic simulations support previous assertions that the trajectories of sinking particles are, for the most part, far from vertical, and that traps sample particles from rather large “catchment” areas when evaluated over long time scales (much greater than 1 year). The dimensions and geographic centers of these catchment areas are determined by the characteristics of the ocean flow field, particle sinking speeds and depth of the traps. The predicted extent and center of the 3200 m OFP trap is nearly identical to that inferred from a previous analysis of OFP trap fluxes and Coastal Zone Color Scanner (CZCS) imagery. Traps moored at different depths may collect particles originating in widely separated areas at the sea surface. This is an important issue when the catchment area is assessed over short time scales (less than 60 days), which typify the collection times of most moored sediment traps. Given the typically patchy distribution of particles and particle producers, this can result in short-period flux measurements that show little or no coherence between collections made at the same location for adjacent times or those made simultaneously but at different depths. The effects of eddy dispersion will be greater for most other oceanic regions, as the Sargasso Sea is characterized by relatively low levels of both eddy and mean kinetic energy. The results of this study demonstrate that an understanding of the temporal and spatial characteristics of the flow field above deep-ocean sediment traps is just as important to the interpretation of flux measurements as is the analysis of the material collected by the traps.

Regional estimates of the export flux of particulate organic carbon derived from thorium-234 during the JGOFS EqPac program

Abstract: The upper ocean 234Th activity distribution at 77 stations was measured between 12°N and 10°S, and 95°W and 170°W in the spring and autumn of 1992. A regional scavenging model was used to estimate vertical export of particulate 234Th. Given the relatively high upwelling rates in this region, particularly at equatorial latitudes near 140°W, it was necessary to include upwelling of 234Th in our model in order to quantify particulate export. Using this export flux and the measured organic C or N to 234Th ratio on particles, one can empirically determine POC and PON fluxes for this region. The estimated particulate organic C flux varies spatially and temporally within this region, ranging from 1 to 7 mmol C m−2 day−1, with enhanced export occurring over the equator. Fluxes are also enhanced along 95°W coincident with a low temperature/high nutrient peak at 4°S. Along 140°W, particulate organic C export from the upper 100 m is on the order of 2 mmol C m−2 day−1 at latitudes beyond 4°N and 4°S, with an equatorial peak of 3–5 mmol C m−2 day−1 in both spring and fall. These results suggest that a relatively small per cent of the total production is exported locally on sinking particles (particle export/primary production C 234 Th ratios. Given the measured C N ratio, particulate N fluxes from the upper 100 m would be 6 times lower than for POC.

Westerly Wind Bursts: ENSO’s Tail Rather than the Dog?.

Abstract: Westerly wind bursts (WWBs) in the equatorial Pacific occur during the development of most El Nino events and are believed to be a major factor in ENSO’s dynamics. Because of their short time scale, WWBs are normally considered part of a stochastic forcing of ENSO, completely external to the interannual ENSO variability. Recent observational studies, however, suggest that the occurrence and characteristics of WWBs may depend to some extent on the state of ENSO components, implying that WWBs, which force ENSO, are modulated by ENSO itself. Satellite and in situ observations are used here to show that WWBs are significantly more likely to occur when the warm pool is extended eastward. Based on these observations, WWBs are added to an intermediate complexity coupled ocean–atmosphere ENSO model. The representation of WWBs is idealized such that their occurrence is modulated by the warm pool extent. The resulting model run is compared with a run in which the WWBs are stochastically applied. The modulation of WWBs by ENSO results in an enhancement of the slow frequency component of the WWBs. This causes the amplitude of ENSO events forced by modulated WWBs to be twice as large as the amplitude of ENSO events forced by stochastic WWBs with the same amplitude and average frequency. Based on this result, it is suggested that the modulation of WWBs by the equatorial Pacific SST is a critical element of ENSO’s dynamics, and that WWBs should not be regarded as purely stochastic forcing. In the paradigm proposed here, WWBs are still an important aspect of ENSO’s dynamics, but they are treated as being partially stochastic and partially affected by the large-scale ENSO dynamics, rather than being completely external to ENSO. It is further shown that WWB modulation by the large-scale equatorial SST field is roughly equivalent to an increase in the ocean–atmosphere coupling strength, making the coupled equatorial Pacific effectively self-sustained.