Temperature and salt balances on Georges Bank February–August 1995

Abstract

Temperature and salinity variability over the crest and southern flank of Georges Bank are investigated using moored observations obtained from February to August 1995 and historical data. There was a large seasonal variation in water temperature, which decreased 1°C–2°C in February to a minimum of 5°C due to surface cooling and wind‐forced cross‐bank advection, and then increased steadily due to surface heating, reaching 10°C (southern flank) to 17°C (crest) in August. The crest warmed more than the southern flank because it is shallower. Temperature variability at shorter timescales (days to weeks) was primarily due to surface heating on the crest and horizontal advection on the southern flank. Salinity variability over the southern flank was primarily associated with two processes. Intrusions of warm, salty, shelf‐slope‐front water in May and August were associated with Gulf Stream warm‐core rings, but did not cause longer‐term changes on the southern flank or penetrate onto the crest. Alongbank advection brought low‐salinity, cool Scotian Shelf Water to the southern flank sites in March and early May, about three weeks after crossing the Northeast Channel onto the northeastern flank of Georges Bank (≈130 km away). This low‐salinity water on the southern flank in the spring did not penetrate immediately onto the crest. Instead, the crest salinity steadily decreased from April to August due to both precipitation (evaporation was small) and, based on historical data, a tidally forced, cross‐frontal exchange flow (0.01–0.02 m s−1) that both freshens and cools the crest.

Heat and salt balances over the New England continental shelf, August 1996 to June 1997

“…[9] The CMO moored array consisted of four sites located on the outer half of the New England continental shelf south of Cape Cod, Massachusetts [Lentz et al, 2003b;Shearman and Lentz, 2003]. A heavily instrumented central site on the 70-m isobath was surrounded by three more lightly instrumented sites, an inshore site 11 km onshore of the central site in 64 m of water, an offshore site 12.5 km offshore of the central site in 86 m of water, and an alongshore site 14.5 km east of the central site in 69 m of water (Figure 1).…”

“…Lentz et al [2003b] used a 6-month moored array deployment to examine the heat balance at mid-shelf on the southern flank of Georges Bank, to the northeast of the New England shelf. They found that the seasonal increase in temperature from February to August 1995 was primarily due to surface heating while advective heat fluxes dominated the temperature variability over time scales of days to weeks.…”

“…These studies suggest there is an onshore flux of salt at the shelf break but the magnitude is poorly constrained. However, there has been only one study that provided direct estimation of the terms in the local salt balance in the region, the study on the southern flank of Georges Bank [Lentz et al, 2003b]. They found that salinity variations were dominated by advection, notably movement of saltier slope water onto the southern flank of Georges Bank.…”

On the cause of Scotian Shelf Water crossovers

“…Temperature and salinity of shelf water on Georges Bank and off-bank slope water change seasonally [Flagg, 1987;Wright and Parker, 1976;Lentz et al, 2002]. Temperature and salinity for shelf water are about 5°C and 33.2 (1026.25 kg/m 3 in density) and for upper slope water about 10°C and 35 (1026.95 kg/m 3 ) in winter, whereas they are about 15°C and 33 (1024.43 kg/m 3 ) and about 21°C and 35 (1024.50 kg/m 3 ) in summer, respectively.…”

Influência do campo de ventos e do meandramento da Corrente do Brasil na concentração de clorofila-<i>a</i> e nutrientes ao largo de Ubatuba - SP

“…A coerência entre o transporte de Ekman calculado pela tensão de cisalhamento do vento e a temperatura de fundo em diversos sistemas costeiros foi observada por autores como de Szoeke e Richman (1984), Mitchum e Clarke (1986), Lentz (1995Lentz ( , 2001), Samelson (1997), Austin e Lentz (2002). Austin e Barth (2002) O vento de nordeste pode gerar dois tipos de ressurgência, uma ressurgência local devido ao transporte de Ekman, e outra remota, provocada pelo transporte barotrópico de águas ressurgidas ao longo da costa.…”