Interannual variability of temperature and salinity in shallow water: Long Island Sound, New York

Abstract

[1] Variabilities of temperature and salinity over Long Island Sound (LIS), New York, are examined using observations from 1991 to 2002. There is a strong seasonal variation in the temperature, and its interannual variability is characterized by a higher variance during winter than summer. The salinity exhibits regular seasonal patterns driven by freshwater input, but there is a long-term change throughout LIS. Anomaly maps of temperature and salinity indicate strong longitudinal gradients increasing in the westward direction. Empirical orthogonal function analyses indicate that the first modes of temperature and salinity anomalies can explain 87% and 89% of the total variances, respectively. The first mode principle components of the temperature and salinity anomaly contain quasi-biennial periodicities. The salinity anomaly also contains an additional signal at a decadal timescale. Seasonal variations in the temperature and salinity are primarily associated with heat flux and freshwater discharge. However, the surface heat flux anomaly only accounts for 17% of the total variance of the time rate change of the temperature anomaly, and the freshwater discharge anomaly explains 25% of the variance of the salinity anomaly. Contrary to traditional paradigm about estuaries, this result shows that forcings other than local processes control the interannual variabilities of the temperature and salinity in LIS, most probably through horizontal exchanges. Also, the significant correlation between the salinity anomaly and the Gulf Stream (GS) position suggests that the interannual variability of salinity in LIS is possibly connected to shelf slope water properties associated with changes in the GS position.Citation: Lee, Y. J., and K. Lwiza (2005), Interannual variability of temperature and salinity in shallow water: Long Island Sound, New York,

Importance of the bacterial dynamics in model simulations of seasonal hypoxia

“…Previous studies in western LIS indicate that variations in salinity are controlled by seasonal cycles of freshwater input from the East, Harlem, Connecticut and Hudson Rivers (Lee and Lwiza 2005), tidal and wind mixing, exchange with the ocean and balance between precipitation and evaporation (Lee and Lwiza 2005;O'Donnell et al, 2013;Whitney, 2010). Our model accurately reproduced major variability in observed salinity, and provided reasonable representation of water column structure for DO simulation.…”

Interannual surface salinity on Northwest Atlantic shelf

“…Over the longer period (1993–2015), salinity variations on the shelf also lead the GSNW latitude shifts, but the lagged correlation is weaker (∼0.35). The latter estimate is line with values reported by Lee and Lwiza [] and suggests that factors other than Gulf Stream front excursions contribute to the interannual variability of shelf water properties.…”

“…The GSNW may serve as a proxy for variable slope water properties. Indeed, it moderately correlates with interannual salinity even in the inner shelf regions like the Long Island Sound ( at zero lag) [ Lee and Lwiza , ].…”

Estimates of horizontal fluxes of oxygen, heat, and salt in western Long Island Sound

“…Since the residual upwelling term from equation , , would create additional heat losses, this estimate represents a lower bound on the downward heat flux needed to close the budget. This estimate of the lower bound of the downward heat flux is consistent with the estimates made by McCardell and O'Donnell [] of downward across‐pycnocline heat fluxes during July and August of 2004 at EXRK of 100–400 W m −2 and with those made by Lee and Lwiza [] who estimated summertime net downward surface heat fluxes to be 150–200 W m −2 . Our estimates also indicate the variability in these fluxes at the 5 day scale is of similar magnitude to the fluxes themselves.…”