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

Abstract

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.

Growth Response of Arctica Islandica to North Atlantic Oceanographic Conditions Since 1850

“…The positive correlations between A. islandica SGI and winter temperature at different bathymetric levels in Station 27 seem to confirm that a warmer LC inshore branch during winter enhances A. islandica growth in SPM. This result seems consistent with our previous findings, as warmer winter conditions on the Newfoundland shelf are related to NAO negative phase (Wanner et al, 2001), stronger LC flowing equatorward passing the Tail of the Grand Banks (Han et al, 2014), southward shift of the SSF (Peterson et al, 2017) allowing penetration of LC nutrient rich water into SPM region. The lack of correlations between our chronology and Station 27 temperatures above 100 m depth from March to December (stratified period) is quite certainly related to local (Eastern Newfoundland) atmospheric phenomena which are probably not the same as at SPM.…”

“…Correlations between A. islandica growth and SSF positions were always negative, meaning that a northward shift of warm slope water leads to decreased A. islandica shell growth in SPM. The positive correlation between shell growth and westward transport and negative correlation between shell growth and northward extension of the SSF could be explained by the recent study of Peterson et al (2017). They showed that the "SSF is the surface expression of the southwestward extension of the Labrador Current."…”

“…This possibility led us to investigate the Tail of the Grand Banks circulation (Figure 1) which was already known to affect the SPM region under certain conditions (Petrie and Drinkwater, 1993;Peterson et al, 2017). A part of the offshore branch of LC that follows the continental slope retroflexes to the east, joining the North Atlantic Current before reaching the Tail end of the Grand Banks (Fratantoni and McCartney, 2009).…”

Refinement and utilization of the marine climate proxy Arctica islandica: An ideal replication strategy for stable isotope studies and an investigation into the shell growth and hydrographic variability of Georges Bank (Northwestern Atlantic)

“…A positive NAO coincides with a decrease in shell growth, when shell growth lags the NAO by about two years. A two-year lag between these records corresponds with previous studies that found it takes 1-2 years for the North Atlantic to respond to changes in the NAO/AO (Taylor and Stephens, 1998;Mountain et al, 2012;Peterson et al, 2017).…”

Assessing Coastal SMAP Surface Salinity Accuracy and Its Application to Monitoring Gulf of Maine Circulation Dynamics

“…Key water mass inflows influencing this marginal sea include the upstream fresh/cold Scotian Shelf and Labrador Sea currents, and the adjoining salty/warm northwestern (NW) Atlantic shelf (Mountain [1]; Townsend et al [2]; Feng et al [3]; Peterson et al [4]). The primary inflow to the GoM is through The dominance of subsurface GoM exchange pathways has, so far, limited the utility of surface remote sensing data for monitoring GoM dynamics.…”