Western boundary circulation and coastal sea-level variability in Northern Hemisphere oceans

Abstract

Abstract. The northwest basins of the Atlantic and Pacific oceans are regions of intense western boundary currents (WBCs): the Gulf Stream and the Kuroshio. The variability of these poleward currents and their extensions in the open ocean is of major importance to the climate system. It is largely dominated by in-phase meridional shifts downstream of the points at which they separate from the coast. Tide gauges on the adjacent coastlines have measured the inshore sea level for many decades and provide a unique window on the past of the oceanic circulation. The relationship between coastal sea level and the variability of the western boundary currents has been previously studied in each basin separately, but comparison between the two basins is missing. Here we show for each basin that the inshore sea level upstream of the separation points is in sustained agreement with the meridional shifts of the western boundary current extension over the period studied, i.e. the past 7 (5) decades in the Atlantic (Pacific). Decomposition of the coastal sea level into principal components allows us to discriminate this variability in the upstream sea level from other sources of variability such as the influence of large meanders in the Pacific. Our result extends previous findings limited to the altimetry era and suggests that prediction of inshore sea-level changes could be improved by the inclusion of meridional shifts of the western boundary current extensions as predictors. Long-duration tide gauges, such as Key West, Fernandina Beach or Hosojima, could be used as proxies for the past meridional shifts of the western boundary current extensions.

Extended Water Level Trends at Long‐Record Tide Gauges Via Moving Window Averaging and Implications for Future Coastal Flooding

“…Another possible connection not explored here could be the role of western boundary currents (WBCs), which have recently been observed to exhibit significant changes in intensity and in the positions of extension currents (Caesar et al., 2018; Diabaté et al., 2021; Fu et al., 2020; Qiu et al., 2014; Sasaki et al., 2014; Shears & Bowen, 2017). Most locations where strong positive changes in total water level rates were observed are in the vicinity of WBCs, and the observed shifts in EWL may be due to the direct influence that changing WBCs can have on MSL as well as indirect impacts to tides and annual or seasonal cycles.…”

Influence of Deep‐Ocean Warming on Coastal Sea‐Level Decadal Trends in the Gulf of Mexico

“…Previous efforts to explain coastal RSL rise in the GoM and along the US east coast reveal the influence of diverse physical processes (Harvey et al., 2021) including: VLM (Kolker et al., 2011; Liu et al., 2020), shifting atmospheric patterns (Piecuch et al., 2016; Thompson et al., 2016), changes in the dynamical link to western boundary current flow (Diabate et al., 2021; Ezer & Dangendorf, 2020), near‐coast bathymetric geometry (Wise et al., 2018), low frequency internal natural variability (Dangendorf et al., 2023), and the connection to larger‐scale North Atlantic ocean heat uptake (Volkov et al., 2019). Key results highlight the coherence of coastal sea‐level variations south of Cape Hatteras and that land subsidence in the western GoM contributes significantly to local RSL rise.…”

What Forcing Mechanisms Affect the Interannual Sea Level Co‐Variability Between the Northeast and Southeast Coasts of the United States?

“…Interannual sea‐level variations along the East Coast of the United States (U.S.) have been a subject of many studies, because sea‐level rise (SLR) rate in that region exceeded the global mean SLR rate, posing a serious threat to the densely populated and economically important coastal communities (Andres et al., 2013; Little et al., 2017, 2021; Piecuch et al., 2016; Sallenger et al., 2012; Thompson, 1986; Valle‐Levinson et al., 2017; Wang et al., 2022; Woodworth et al., 2014, 2017, 2019; Yin & Goddard, 2013). On interannual through decadal timescales, sea‐level variations along the U.S. Northeast and Southeast Coasts, separated by Cape Hatteras, are distinctively more coherent within each sector than between the two sectors (Calafat et al., 2018; Diabaté et al., 2021; Ezer, 2019; Piecuch et al., 2016; Thompson, 1986). Probably because of this reason, many studies of sea‐level variations along the U.S. East Coast focused on one sector, or even subregions within a particular sector.…”

“…timescales, sea-level variations along the U.S. Northeast and Southeast Coasts, separated by Cape Hatteras, are distinctively more coherent within each sector than between the two sectors (Calafat et al, 2018;Diabaté et al, 2021;Ezer, 2019;Piecuch et al, 2016;Thompson, 1986). Probably because of this reason, many studies of sea-level variations along the U.S. East Coast focused on one sector, or even subregions within a particular sector.…”