Salinity maximum in the pycnocline of the Middle Atlantic Bight1,2

Gordon, Arnold L.; Aikman, Frank

doi:10.4319/lo.1981.26.1.0123

Cited by 43 publications

(21 citation statements)

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“…Standard deviations of the depth-averaged temperature (100-km along-isobath bins) are relatively constant (18-1.58C) from Georges Bank to Delaware Bay and then increase as the 70-m isobath gets near the shelf break and encounters both shelf water and the warmer slope and Gulf Stream water. Occasional, relatively warm, individual depthaveraged temperatures (.158C) evident throughout the MAB are probably warm salty intrusions of slope water (e.g., Gordon and Aikman 1981;Churchill 1985;Flagg et al 1994;Lentz et al 2003c). These general features of the along-isobath distribution of depth-averaged temperatures are also evident along the 30-, 50-, and 90-m isobaths.…”

Section: A Along-isobath Heat Balancementioning

confidence: 99%

The Mean Along-Isobath Heat and Salt Balances over the Middle Atlantic Bight Continental Shelf

Lentz

2010

Journal of Physical Oceanography

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The mean heat and salt balances over the Middle Atlantic Bight continental shelf are investigated by testing the hypothesis that surface fluxes of heat or freshwater are balanced by along-isobath fluxes resulting from the mean, depth-averaged, along-isobath flow acting on the mean, depth-averaged, along-isobath temperature or salinity gradient. This hypothesized balance is equivalent in a Lagrangian frame to a column of water, for example, warming because of surface heating as it is advected southward along isobath by the mean flow.Mean depth-averaged temperatures increase from north to south along isobath at a rate of 28C (1000 km) 21at midshelf, which is consistent with the hypothesized balance and mean surface heat flux estimates from the 50-yr NCEP Reanalysis. However, mean surface heat flux estimates from the higher-resolution 20-yr Objectively Analyzed Air-Sea Fluxes (OAFlux) reanalysis are too small to balance the along-isobath heat flux divergence implying a cross-shelf heat flux convergence. It is unclear which surface heat flux estimate, NCEP or OAFlux, is more accurate. The cross-shelf heat flux convergence resulting from the mean cross-shelf circulation is too small to balance the along-isobath heat flux divergence. Mean depth-averaged salinities increase from north to south along isobath at a rate of 1 (psu) (1000 km) 21at midshelf. Mean precipitation and evaporation rates nearly balance so that the net freshwater flux is too small by more than an order of magnitude to account for the observed along-isobath increase in salinity. The cross-shelf salt flux divergence resulting from the mean cross-shelf circulation has the wrong sign to balance the divergence in the along-isobath salt flux. These results imply there must be an onshore ''eddy'' salt flux resulting from the time-dependent current and salinity variability. The along-isobath temperature and salinity gradients compensate for each other so that the mean, depthaveraged, along-isobath density gradient is approximately zero. This suggests that there may be a feedback between the along-isobath density gradient and the onshore salt and heat fluxes that maintains the density gradient near zero.

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Section: A Along-isobath Heat Balancementioning

confidence: 99%

The Mean Along-Isobath Heat and Salt Balances over the Middle Atlantic Bight Continental Shelf

Lentz

2010

Journal of Physical Oceanography

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“…Increasing insolation and freshwater input and decreasing wind stress during the spring promote the development of stratification, eventually obliterating the shelf-slope front above the seasonal thermocline. Interleaving of the two water masses increases (Voorhis et al 1976;Flagg et al 1994), and they become connected along isopycnal surfaces, facilitating exchange (Gordon and Aikman 1981;Houghton et al 1988). Nutrient depletion develops in the upper ϳ20-30 m of the shelf by ca.…”

mentioning

confidence: 99%

Enhanced chlorophyll at the shelfbreak of the Mid‐Atlantic Bight and Georges Bank during the spring transition

Ryan

Yoder

Cornillon

1999

Limnology & Oceanography

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In 8 yr (1979)(1980)(1981)(1982)(1983)(1984)(1985)(1986) of Coastal Zone Color Scanner (CZCS) imagery, we find annual enhancement of chlorophyll at the shelfbreak of the Mid-Atlantic Bight (MAB) and Georges Bank during the spring transition from well-mixed to stratified conditions. Spatial and temporal extents of enhancement vary interannually, and expression is intermittent intraannually. This feature can span the entire MAB and southern flank of Georges Bank (ϳ1,100 km) and can be expressed for as long as 10 weeks (mid-April to late June). Pigment concentrations within the feature average more than two times that of adjacent shelf and slope waters. Enhanced shelfbreak chlorophyll consistently coincided with the shelf-slope front and often extended inshore of the surface outcrop of the front a few to ϳ10 km. In all years except 1986, it coincided with seaward entrainment of shelf water by Gulf Stream warm-core rings (WCRs) or meanders. Shelfbreak chlorophyll enhancement was most pronounced during 1980. Using satellite and in situ observations, we found that during 1980, it coincided with the shelf-slope front for 10 weeks, and, unlike the spring bloom, it was dominated by the nanophytoplankton (Ͻ20 m) size fraction. During the peak of the 1980 occurrence, four WCRs simultaneously interacted with shelf water, and chlorophyll enhancement inshore of one WCR coincided with a slope-water intrusion onto the shelf. Empirical orthogonal function (EOF) decomposition of CZCS images for late March-June 1980 showed that shelfbreak enhancement was strongly pronounced in an EOF that accounted for Ͼ10% of the variance about the mean. This annual biological feature, brought to light in satellite ocean color imagery, is an important aspect of the shelf-slope ecology of the MAB and Georges Bank.

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“…This diapycnal mixing also led to inflated particle counts in the highly stratified slope waters, particularly in the smallest size range (100-400 pixels). Flattening of isopycnals at the thermocline during the summer stratified months has been documented previously (Barth et al, 2004;Houghton et al, 1988), with strongest density changes containing intrusions of salty slope water onto the shelf (Gordon and Aikman, 1981). Because many characteristics documented by ISIIS were consistent with previous studies of the shelf-slope front, it is likely that frontal circulation patterns, including bottom boundary convergence, upwelling along isopycnals, and a strong southward flowing frontal jet (Chapman and Lentz, 1994;Houghton and Visbeck, 1998;Mann and Lazier, 2006), were occurring during this study.…”

Section: Physical Environment At the Frontmentioning

confidence: 56%

Fine-scale planktonic habitat partitioning at a shelf-slope front revealed by a high-resolution imaging system

Greer

Cowen

Guigand³

et al. 2015

Journal of Marine Systems

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Salinity maximum in the pycnocline of the Middle Atlantic Bight1,2

Abstract: This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.

Cited by 43 publications

References 9 publications

The Mean Along-Isobath Heat and Salt Balances over the Middle Atlantic Bight Continental Shelf

The Mean Along-Isobath Heat and Salt Balances over the Middle Atlantic Bight Continental Shelf

Enhanced chlorophyll at the shelfbreak of the Mid‐Atlantic Bight and Georges Bank during the spring transition

Fine-scale planktonic habitat partitioning at a shelf-slope front revealed by a high-resolution imaging system

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