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Decadal Variability Of The Gulf Stream North Wall Position And Its Connection To Ocean Heat Content
  • Alexey Mishonov,
  • Dan Seidov,
  • James Reagan
Alexey Mishonov

Corresponding Author:alexey.mishonov@noaa.gov

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Dan Seidov
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James Reagan
ESSIC - University of Maryland
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To trace the Gulf Stream (GS) path across five decades from 1965 to 2017, we mapped the annually averaged positions of the Gulf Stream North Wall (GSNW) defined by the 15°C isotherm at 200 m depth computed using in situ seawater temperature records from the World Ocean Database 2018 (WOD18). Inter-annual GSNW variability is noticeably different west and east of ~50°W. There are two distinct variability zones west and east of that longitude—a zone with a rather narrow envelope (~3° of latitude-wide) west and a zone with a twice as wide envelope (~ 6° of latitude-wide) east of that longitude. The more disperse annual pathways are near the Mid-Latitude Transition Zone. Moreover, within the ~50-year timeline, the quasi-decadal period of 2005–2017 is marked by far larger spread in the annual GSNW positions than the previous decades, especially between 50°W and 40°W. The principal conclusion of our analysis, is that the GS between Cape Hatteras and the Grand Banks (west of 50°W) is not only stiff but maintains its position with astounding resiliency. The GSNW average position along that stretch of longitudes migrates slowly northward as a whole, but it is unlikely that such a slow and spatially insignificant migration could cause substantial changes in the Atlantic Meridional Overturning Circulation (AMOC). In contrast, near the Grand Banks (east of 50°W), the GSNW northward shift is quite noticeable—over 2.6° in latitude over ~50 years—and thus could have some impacts on the AMOC long-term dynamics. There are significant correlations between the GSNW and Ocean Heat Content (OHC) variability east of 50°W that may be critical for the GS path resilience and its future changes over decadal and longer time scales. Furthermore, the significant correlations between OHC and GSNW in the extension zone rose from r=0.5 for annual to r=0.8 for pentadal to r=0.9 decadal time scales. We assert that the OHC may become the best indicator of the GS path’s variability on decadal and longer time scales.