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Abstract: Ocean circulation influences nearly all aspects of the marine ecosystem. This study describes the water circulation patterns on time scales from hours to years across Torres Strait and adjacent gulfs and seas, including the north of the Great Barrier Reef. The tridimensional circulation model incorporated realistic atmospheric and oceanographic forcing, including winds, waves, tides, and large-scale regional circulation taken from global model outputs. Simulations covered a hindcast period of 8 years (i.e. 01/03/1997–31/12/2004), allowing the tidal, seasonal, and interannual flow characteristics to be investigated. Results indicated that the most energetic current patterns in Torres Strait were strongly dominated by the barotropic tide and its spring-neap cycle. However, longer-term flow through the strait was mainly controlled by prevailing winds. A dominant westward drift developed in summer over the southeasterly trade winds season, which then weakened and reversed in winter over the northwesterly monsoon winds season. The seasonal flow through Torres Strait was strongly connected to the circulation in the north of the Great Barrier Reef, but showed little connectivity with the coastal circulation in the Gulf of Papua. Interannual variability in Torres Strait was highest during the monsoon period, reflecting variability in wind forcing including the timing of the monsoon. The characteristics of the circulation were also discussed in relation to fine sediment transport. Turbidity level in Torres Strait is expected to peak at the end of the monsoon, while it is likely to be at a low at the end of the trade season, eventually leading to a critically low bottom light level which constitutes a severe risk of seagrass dieback. [Copyright &y& Elsevier]

Abstract: The seasonal cycles of some atmospheric parameters at Cochin (southwest coast of India) have been studied with a specific emphasis on the role played by them in forcing the seasonal sea level. Equatorward along-shore wind stress as well as equatorward volume transport by coastal currents along the Indian peninsula could play an important role in the sea level low during the premonsoon and southwest monsoon seasons. During postmonsoon season, along-shore wind stress plays no major role in the high sea level whereas this could be due to the poleward volume transport by the coastal along-shore currents. Atmospheric pressure and river discharge do not seem to influence much the sea level during the southwest monsoon period, even though the river discharge during that period is considerable. The sea level was minimal during the southwest monsoon season, when the river discharge was at its annual maximum. The difference between the seasonal march of observed and pressure corrected sea level (CSL) was not significant for the study region. Harmonic analysis of the climatological data on the various parameters revealed that air temperature is the only parameter with a dominance of the semi-annual over the annual cycle. Cross-shore wind stress indicated strong interannual variability whereas relative density showed strong seasonal variability. The climatological seasonal cycles of CSL at eight other tide gauge stations along the west coast of the Indian subcontinent are also examined, to assess the role of various forcings on the seasonal sea level cycle. The signatures of El Nino-Southern Oscillation (ENSO) phenomenon could be seen in some of the parameters (SST, air temperature, atmospheric pressure, along-shore wind stress, relative density and sea level). The signature of ENSO was particularly strong in the case of atmospheric pressure followed by relative density, the variance accounted by the relationship being 47% and 16%, respectively. [Copyright &y& Elsevier]

Abstract: The present study of temporal and spatial variations of shore-fast ice in the Kara Sea includes utilization of aircraft observations by the Arctic and Antarctic Research Institute (AARI) from 1953 to 1990, and surface brightness temperature from SSM/I from 1987 to 2001. Analyses of a time series of spatially distributed SSM/I brightness temperatures provide estimates of the shore-fast ice extent. The present work shows spatial distributions of frequencies of shore-fast ice coverage in the Kara Sea for each month, and it gives a time series of its area. The fast ice extent in early spring typically reaches a stable configuration, which falls into one of two different categories (modes) with significantly different area. The smaller of these two modes tends to appear with increased frequency since 1980. This gives, for this period, a negative trend in fast ice area during spring. There is a correlation above 0.5 between the average winter temperature and maximum ice thickness anomalies and fast ice area. Analysis of surface wind data and sea level pressure indicates that wind during winter controls much of the shore-fast ice development. Specially strong westerly and southwesterly winds tend to give a smaller fast ice extent than otherwise. Variations in river discharge tend only to have an observable effect on the ice at the river mouths. [Copyright &y& Elsevier]

This project examines the role of local atmospheric forcing during the transition from relatively cold wintertime to relatively warmer springtime temperatures in the northern Middle Atlantic Bight (MAB) region during 1965–1973. A one-dimensional water column model is run for eight consecutive winter seasons with local surface heat flux used as the only external forcing. Historical data from the Nantucket Light Ship, along with modeled radiation estimates for New York and Boston are used for the heat flux calculations. Two model simulations were made for each winter season, allowing for both a qualitative and quantitative comparison of model output with observed regional temperature variability and with observed temperature changes measured at Nantucket Lightship (NLS). Interannual variability (IAV) in local atmospheric heat flux during wintertime is shown to be a dominant factor in determining springtime temperature conditions during the study period. However, the residuals from a regression analysis suggest that advective processes may have contributed to the observed temperature variability, although it is believed that the advective influence is secondary to local surface heat flux in the northern MAB for this study period. [Copyright &y& Elsevier]

We examine the first in situ velocity data collected on the shelf of Southern Brazil. The mooring station with two current meters was deployed at 32°41′S, 51°27′W on March 4, 1997, and recovered on August 2, 1997. Also analyzed are wind data for the same period obtained at a nearby coastal meteorological station. The observed velocity series can be interpreted as a sum of highly variable flow correlated with local wind stress and a “residual” mean current flowing northward along the shore at a few centimetres per second. In winter, the currents observed in the bulk of the water column exhibited a dramatic decrease in magnitude, as compared to the remainder of the series, although there was no similar decay of winds. We hypothesize that this is due to the impact of very stable salinity controlled winter stratification in a narrow subsurface layer because of enhanced river discharges that effectively isolates the deeper layers from atmospheric forcing. The frequency band corresponding to the periods from 2 to 10 days, presumably associated with meteorological forcing, dominated the velocity spectrum. The tidal currents were weak and predominantly diurnal. [Copyright &y& Elsevier]

TELEMAC-2D, a two-dimensional depth-averaged finite element flow model, has been chosen for modelling the hydrodynamics of the Patos Lagoon during the 1998 El Nin˜o event. The model is initially calibrated against measurements carried out between 20 and 29/10/98, and good agreement is achieved between measured and predicted longitudinal velocities. Model validation is carried out by comparing measurements and predictions for one reference station in the estuarine area for the period between 23/05 and 06/06/98. Results indicate an excellent agreement between measurements and predictions, and the model is considered calibrated and validated for the Patos Lagoon hydrodynamics.A study of the Patos Lagoon hydrodynamics under the El Nin˜o extreme conditions shows that the local and non-local wind effects associated with the freshwater discharge at the top of the lagoon promote longitudinal and lateral set-up/set-down mechanisms that influence the circulation. Results indicate that velocities in the lagoon and estuary during the extreme conditions observed in the El Nin˜o period are much stronger than the normal periods.The response of the Patos Lagoon entrance to the local and non-local forcing is studied for the first time in terms of the inflow and outflow of water in the system. Results indicate that during the 1998 El Nin˜o event the non-local forcing dominated, promoting exchanges that represent around 7% of the lagoon initial volume in the simulation. Strong freshwater discharges at the top of the lagoon combined with pressure gradients due to changes in elevation generated by the local and non-local wind favours the predominant seawards flow at the mouth, with outflows in the order of 5000 m3 s−1. The strong outflow observed during the El Nin˜o extreme flow conditions generates huge plumes of freshwater into the adjacent coastal area. [Copyright &y& Elsevier]

The structure of the wind-induced exchange between Indian River Bay, Delaware and the adjacent continental shelf is examined based on current measurements made at the Indian River Inlet which represents the only conduit of exchange between the bay and the coastal ocean. Local wind measurements and sea levels from stations located along the open coast and in the interior of the bay are also obtained. Coastal sea level fluctuations are coherent with winds over periodicities of 2–10 days, with the highest response corresponding to winds aligned along two bands, one broadly centered around the general orientation of the Middle Atlantic Bight coastline between New Jersey and Virginia (040°T), and the other narrowly focused on the direction perpendicular to the local coastline (090°T). Currents in the inlet are also highly coherent with the wind along these two directions, but the high coherence is limited to time scales between 2 and 5 days. Within those time scales the currents in the inlet show largely depth-independent fluctuations which are highly coherent and in quadrature phase with the coastal sea level fluctuations, indicating that the subtidal exchanges in those time scales are principally accomplished by the remote wind effects on the shelf through the impingement of coastal sea level fluctuations at the entrance to the inlet. This coastal pumping effect produces unidirectional inflow throughout the water column under coastal set-up conditions, and outflow occurs under coastal set-down conditions. There is indication that a weaker, but still significant mode of bi-directional exchange also exists in the inlet, with currents in the upper layer fluctuating in opposite directions relative to those in the lower layer. [Copyright &y& Elsevier]