Interannual variability of the shelf-slope front position between 75° and 50° W

Subsurface temperatures in the Slope Water region of the Northwest Atlantic from Argo profiling floats and on the adjacent continental shelf from ship‐based measurements are compared with the latitudinal position of the Shelf‐Slope Front (SSF) and the Gulf Stream North Wall (GSNW). The Slope Water and shelf temperature anomalies at 200 m depth are in agreement for the period, 2002–2015. For the period 1978–2015, shelf temperatures are significantly correlated with the SSF position, and to a lesser extent with the GSNW position. Annual SSF position anomalies near the Grand Banks at 50°W–55°W lead anomalies to the west at 65°W–75°W by 1–2 years. Wind stress curl is compared with the annual change in the SSF and GSNW latitudinal positions, rather than with the positions directly. Changes in the mean position of the SSF are related to the wind stress curl pattern in the mid‐Atlantic, with an 8 month lag. It is suggested that a wind pattern favoring a southward shift of the SSF is associated with a southward shift of the zero‐curl line near 40°W, resulting in an expanded subpolar gyre and enhanced flow of Labrador Current Water westward from the Tail of the Grand Banks. However, changes in the GSNW position are related to an NAO‐like wind stress curl pattern in the eastern Atlantic in the winter‐spring period, in agreement with other studies. High sea surface temperatures in the Gulf of Maine and on the Scotian Shelf in recent years can be largely attributed to positive local onshore wind anomalies.

show abstract

“…Using a different method, Bisagni et al . [] estimated a lag of 4 years for the annual mean SSF position between 50°W and 75°W.…”

Section: Resultssupporting

confidence: 54%

Variability and wind forcing of ocean temperature and thermal fronts in the Slope Water region of the Northwest Atlantic

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Negative vorticity was clearly identified near the center of the meander. At this time, the surface outcrop of the shelfbreak front in the MAB [ Linder and Gawarkiewicz , ; Bisagni et al ., ] was close to the shelfbreak and oriented parallel to the local isobaths, suggesting that the direct impact of the meander had not yet reached the shelf region.…”

Section: Resultsmentioning

confidence: 99%

Data assimilative modeling investigation of Gulf Stream Warm Core Ring interaction with continental shelf and slope circulation

Chen

Powell

et al. 2014

JGR Oceans

View full text Add to dashboard Cite

A data assimilative ocean circulation model is used to hindcast the interaction between a large Gulf Stream Warm Core Ring (WCR) with the Mid-Atlantic Bight (MAB) shelf and slope circulation. Using the recently developed Incremental Strong constraint 4D Variational (I4D-Var) data assimilation algorithm, the model assimilates mapped satellite sea surface height (SSH), sea surface temperature (SST), in situ temperature, and salinity profiles measured by expendable bathythermograph, Argo floats, shipboard CTD casts, and glider transects. Model validations against independent hydrographic data show 60% and 57% error reductions in temperature and salinity, respectively. The WCR significantly changed MAB continental slope and shelf circulation. The mean cross-shelf transport induced by the WCR is estimated to be 0.28 Sv offshore, balancing the mean along-shelf transport by the shelfbreak jet. Large heat/salt fluxes with peak values of 8900 W m 22 /4 3 10 24 kg m 22 s 21 are found when the WCR was impinging upon the shelfbreak.Vorticity analysis reveals the nonlinear advection term, as well as the residual of joint effect of baroclinicity and bottom relief (JEBAR) and advection of potential vorticity (APV) play important roles in controlling the variability of the eddy vorticity.

show abstract

“…4). Inter-annual variability (IAV) of the surface SBF position at each longitude was computed as the annual mean of the 12 monthly anomalies for each year after removal of the mean annual cycle for each month similar to Bisagni et al (2009).…”

Section: Shelf Break Front (Sbf) Positional Datamentioning

confidence: 99%

“…Unrelated to Ekman forcing, an annual westward-propagating, seaward meander of the SBF occurs between November (at the Tail of the Grand Banks, 50° W) and April (south of Newfoundland, 56° W), corresponding to earlier upstream maximal seasonal transport of the Labrador Current during October near Hamilton Bank (Lazier and Wright, 1993;Bisagni et al, 2006). Inter-annual variability (IAV) of the SBF surface position over the same domain shows alternating periods of westward-propagating offshore (late 1970s, late 1980s, late 1990s) and onshore (early 1980s, early 1990s, early 2000s) annual mean SBF surface position anomalies, thus exhibiting a period of approximately 10 years (Bisagni et al, 2009), possibly related to shelf water volume variations. Moreover, at least from 1977-1999 within the Middle Atlantic Bight (MAB), IAV of the annual mean SBF position does appear related to the MAB-wide mean shelf water volume and salinity anomalies (Mountain 2003), with offshore (onshore) SBF anomalies corresponding to periods with positive (negative) volume and negative (positive) salinity anomalies (Bisagni et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Salinity variability along the eastern continental shelf of Canada and the United States, 1973–2013

Bisagni

2016

Continental Shelf Research

Self Cite

View full text Add to dashboard Cite

Continental shelf waters located off the east coast of Canada and the United States are part of a long shelf current system that is partly comprised of colder, less-saline waters originating from high latitudes, including waters from the North Atlantic sub-polar gyre, along with ice-melt and freshwater input from local rivers. A 41-year analysis (1973-2013) of near-surface salinity (NSS) using three hydrographic datasets (Bedford Institute of Oceanography "Climate", NOAA/ESDIM, and Canadian Marine Environmental Data Service (MEDS)) allowed an examination of NSS variability within 11 continental shelf sub-regions, extending from the southern Newfoundland Shelf of eastern Canada to the DelMarVa/Hatteras Shelf of the United States. Although the periods of record containing sufficient data vary between sub-regions, regional mean NSS values are lowest within the Gulf of St. Lawrence and highest on the DelMarVa/Hatteras shelf, with largest annual variability within the Gulf of St. Lawrence. After removal of outliers, long-term linear trends computed from annual mean NSS were detected along the Newfoundland Shelf (+0.011 y-1), Western Scotian Shelf (-0.007 y-1), Gulf of Maine (-0.014 y-1), Georges Bank (-0.011 y-1), and DelMarVa/Hatteras Shelf (+0.024 y-1). A long-term quadratic fit to annual mean NSS from the Eastern Scotian Shelf displays a salinity increase through 1992 of +0.026 y-1 , decreasing thereafter until 2013 by-0.028 y-1. A quadratic fit for the Western Grand Banks displays a NSS increase through 2007 of +0.022 y-1 , decreasing thereafter through 2013 by-0.006 y-1. Annual mean NSS from the Eastern Grand Banks, Tail of the Grand Banks, Gulf of St. Lawrence, and Middle Atlantic Bight display no long-term trends. Interannual variability (IAV) of NSS residuals shows similar small mean squared error (mse) of 0.02-0.04 for the four northern-most sub-regions (Newfoundland Shelf, Eastern, Tail and Western Grand Banks) and are correlated at 0-year lag. IAV of NSS residuals (mse) are larger for the Gulf of St. Lawrence (~0.19), Eastern and Western Scotian Shelf (~0.09-0.06), Gulf of Maine and Georges Bank (~0.08-0.06), Middle Atlantic Bight (~0.19), and maximal for the DelMarVa/Hatteras Shelf (~0.36), and are also correlated at 0-year lag, but are uncorrelated with the four northern-most sub-regions. Consideration of a simple "flux variation" model that includes along-shelf, altimeter-derived velocity anomalies measured upstream on the Western Scotian Shelf and the positive along-shelf mean salinity gradient between the Eastern Scotian Shelf and the DelMarVa/Hatteras Shelf, may explain the synchronous nature of NSS residuals for the southern-most 6 sub-regions. Furthermore, the flux variation model results in calculated NSS residuals that are within a factor of two of observed NSS residuals for the southern-most DelMarVa/Hatteras Shelf. Co-varying broad-scale coastal sea level and shelf break front position anomalies also support the flux variation model, as do CMV Oleander temperature anomalies across a limited Midd...

show abstract

Interannual variability of the shelf-slope front position between 75° and 50° W

Cited by 18 publications

References 45 publications

Variability and wind forcing of ocean temperature and thermal fronts in the Slope Water region of the Northwest Atlantic

Variability and wind forcing of ocean temperature and thermal fronts in the Slope Water region of the Northwest Atlantic

Data assimilative modeling investigation of Gulf Stream Warm Core Ring interaction with continental shelf and slope circulation

Salinity variability along the eastern continental shelf of Canada and the United States, 1973–2013

Contact Info

Product

Resources

About