Western boundary circulation and sea level patterns in northern hemisphere oceans

2021 ◽  
Author(s):  
Samuel Diabaté ◽  
Didier Swingedouw ◽  
Joël Hirschi ◽  
Aurélie Duchez ◽  
Philip Leadbitter ◽  
...  
Keyword(s):  
North America ◽  
Sea Level ◽  
Gulf Stream ◽  
Atlantic Coast ◽  
Ocean Dynamics ◽  
Western Boundary ◽  
Tide Gauges ◽  
Sea Level Changes ◽  
Coastal Sea ◽  
The Kuroshio

<p>The sea level changes along the Atlantic coast of the US have received a lot of attention recently because of an increased rate of rise north of the Gulf Stream separation point since the late 1980s (Sallenger et al., 2012 ; Boon, 2012). While sea-level rise is a major issue for coastal community, sea-level measurements in the region are key to understand the past of the nearby Gulf Stream and the large-scale ocean dynamics. Tide gauges on the coastline have measured the inshore sea-level for many decades and provide a unique window on past oceanic circulation. So far, numerous studies have linked the interannual to multi-decadal coastal sea-level changes to ocean dynamics, including the Gulf Stream strength, the divergence of the Sverdrup transport in the basin interior and the Atlantic meridional overturning circulation. However, other studies argue that local and regional processes, such as the alongshore winds or the river discharges, are processes of greater importance to the coastal sea level.</p><p>The general picture in the Atlantic is hence unclear. Yet, the northwest Atlantic is not the only western boundary region where sea-level has been well sampled. In this study we extend the analysis to the northwest Pacific, where links between the state of the Kuroshio and sea-level are evident (Kawabe, 2005; Sasaki et al., 2014). We discuss similarities and dissimilarities between the western boundary regions. We show for each basin, that the inshore sea level upstream the separation points is in sustained agreement with the meridional shifts of the western boundary current extension. This indicates that long duration tide gauges, such as Fernandina Beach (US) and Hosojima (Japan) could be used as proxies for the Gulf Stream North Wall and the Kuroshio Extension state, respectively.</p><p><strong>References:</strong></p><p>Boon, J. D. (2012). Evidence of sea level acceleration at US and Canadian tide stations, Atlantic Coast, North America. Journal of Coastal Research, 28(6), 1437-1445.<strong> </strong></p><p>Kawabe, M. (2005). Variations of the Kuroshio in the southern region of Japan: Conditions for large meander of the Kuroshio. Journal of oceanography, 61(3), 529-537.</p><p>Sallenger, A. H., Doran, K. S., & Howd, P. A. (2012). Hotspot of accelerated sea-level rise on the Atlantic coast of North America. Nature Climate Change, 2(12), 884-888.</p><p>Sasaki, Y. N., Minobe, S., & Miura, Y. (2014). Decadal sea‐level variability along the coast of Japan in response to ocean circulation changes. Journal of Geophysical Research: Oceans, 119(1), 266-275.</p>

scholarly journals Western boundary circulation and coastal sea-level variability in northern hemisphere oceans

2021 ◽  
Author(s):  
Samuel Tiéfolo Diabaté ◽  
Didier Swingedouw ◽  
Joël Jean-Marie Hirschi ◽  
Aurélie Duchez ◽  
Philip J. Leadbitter ◽  
...  
Keyword(s):  
Sea Level ◽  
Western Boundary Current ◽  
Western Boundary ◽  
Tide Gauges ◽  
Sea Level Changes ◽  
Boundary Current ◽  
Western Boundary Currents ◽  
Boundary Currents ◽  
The Past ◽  
Coastal Sea

Abstract. The northwest basins of the Atlantic and Pacific oceans are regions of intense Western Boundary Currents (WBC), the Gulf Stream and the Kuroshio. The variability of these poleward currents and their extension 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 where 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 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 seven (five) 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. This result 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. Conversely, 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.

scholarly journals Global sea level reconstruction for 1900–2015 reveals regional variability in ocean dynamics and an unprecedented long weakening in the Gulf Stream flow since the 1990s

Ocean Science ◽  
2020 ◽  
Vol 16 (4) ◽  
pp. 997-1016
Author(s):  
Tal Ezer ◽  
Sönke Dangendorf
Keyword(s):  
Sea Level ◽  
Gulf Stream ◽  
Tide Gauge ◽  
Meridional Overturning Circulation ◽  
Ocean Dynamics ◽  
South Atlantic Bight ◽  
Regional Variability ◽  
Coastal Sea ◽  
Global Sea Level

Abstract. A new monthly global sea level reconstruction for 1900–2015 was analyzed and compared with various observations to examine regional variability and trends in the ocean dynamics of the western North Atlantic Ocean and the US East Coast. Proxies of the Gulf Stream (GS) strength in the Mid-Atlantic Bight (GS-MAB) and in the South Atlantic Bight (GS-SAB) were derived from sea level differences across the GS. While decadal oscillations dominate the 116-year record, the analysis showed an unprecedented long period of weakening in the GS flow since the late 1990s. The only other period of long weakening in the record was during the 1960s–1970s, and red noise experiments showed that is very unlikely that those just occurred by chance. Ensemble empirical mode decomposition (EEMD) was used to separate oscillations at different timescales, showing that the low-frequency variability of the GS is connected to the Atlantic Multi-decadal Oscillation (AMO) and the Atlantic Meridional Overturning Circulation (AMOC). The recent weakening of the reconstructed GS-MAB was mostly influenced by weakening of the upper mid-ocean transport component of AMOC as observed by the RAPID measurements for 2005–2015. Comparison between the reconstructed sea level near the coast and tide gauge data for 1927–2015 showed that the reconstruction underestimated observed coastal sea level variability for timescales less than ∼5 years, but lower-frequency variability of coastal sea level was captured very well in both amplitude and phase by the reconstruction. Comparison between the GS-SAB proxy and the observed Florida Current transport for 1982–2015 also showed significant correlations for oscillations with periods longer than ∼5 years. The study demonstrated that despite the coarse horizontal resolution of the global reconstruction (1∘ × 1∘), long-term variations in regional dynamics can be captured quite well, thus making the data useful for studies of long-term variability in other regions as well.

scholarly journals River-discharge effects on United States Atlantic and Gulf coast sea-level changes

2018 ◽  
Vol 115 (30) ◽  
pp. 7729-7734 ◽  
Author(s):  
Christopher G. Piecuch ◽  
Klaus Bittermann ◽  
Andrew C. Kemp ◽  
Rui M. Ponte ◽  
Christopher M. Little ◽  
...  
Keyword(s):  
United States ◽  
Sea Level ◽  
River Discharge ◽  
Sea Level Change ◽  
The United States ◽  
Ocean Dynamics ◽  
Sea Level Changes ◽  
Level Change ◽  
Vertical Land Motion ◽  
Coastal Sea

Identifying physical processes responsible for historical coastal sea-level changes is important for anticipating future impacts. Recent studies sought to understand the drivers of interannual to multidecadal sea-level changes on the United States Atlantic and Gulf coasts. Ocean dynamics, terrestrial water storage, vertical land motion, and melting of land ice were highlighted as important mechanisms of sea-level change along this densely populated coast on these time scales. While known to exert an important control on coastal ocean circulation, variable river discharge has been absent from recent discussions of drivers of sea-level change. We update calculations from the 1970s, comparing annual river-discharge and coastal sea-level data along the Gulf of Maine, Mid-Atlantic Bight, South Atlantic Bight, and Gulf of Mexico during 1910–2017. We show that river-discharge and sea-level changes are significantly correlated (p<0.01), such that sea level rises between 0.01 and 0.08 cm for a 1 km3 annual river-discharge increase, depending on region. We formulate a theory that describes the relation between river-discharge and halosteric sea-level changes (i.e., changes in sea level related to salinity) as a function of river discharge, Earth’s rotation, and density stratification. This theory correctly predicts the order of observed increment sea-level change per unit river-discharge anomaly, suggesting a causal relation. Our results have implications for remote sensing, climate modeling, interpreting Common Era proxy sea-level reconstructions, and projecting coastal flood risk.

scholarly journals Bathymetric Influence on the Coastal Sea Level Response to Ocean Gyres at Western Boundaries

2018 ◽  
Vol 48 (12) ◽  
pp. 2949-2964 ◽  
Author(s):  
Anthony Wise ◽  
Chris W. Hughes ◽  
Jeff A. Polton
Keyword(s):  
Sea Level ◽  
Ocean Dynamics ◽  
Western Boundary ◽  
Thermocline Depth ◽  
Vertical Sidewall ◽  
Weakly Nonlinear ◽  
Coastal Sea ◽  
Effective Depth ◽  
Ocean Gyres ◽  
Maximum Penetration

AbstractIt is our aim with this paper to investigate how the presence of a continental shelf and slope alters the relationship between interior ocean dynamics and western boundary (coastal) sea level. The assumption of a flat-bottomed basin with vertical sidewall at the coast is shown to hide the role that depth plays in the net force acting on the coast. A linear β-plane theory is then developed describing the transmission of sea level over variable depth bathymetry as analogous to the steady advection–diffusion of a thermal fluid. The parameter , relating the friction parameter r to the bathymetry depth H and width , is found to determine the contribution of interior sea level to coastal sea level, with small giving maximum penetration and large maximum insulation. In the small (infinite friction) limit the frictional boundary layer extends far offshore, and coastal sea level tends toward the vertical sidewall solution. Adding simple stratification produces exactly the same result but with reduced effective depth and hence enhanced penetration. Penetration can be further enhanced by permitting weakly nonlinear variations of thermocline depth. Wider and shallower shelves relative to the overall scales are also shown to maximize penetration for realistic values of . The theory implies that resolution of bathymetry and representation of friction can have a large impact on simulated coastal sea level, calling into question the ability of coarse-resolution models to accurately represent processes determining the dynamic coastal sea level.

Evolution of marine climates of the U.S. Atlantic coast during the past four million years

1988 ◽  
Vol 318 (1191) ◽  
pp. 661-678 ◽  
Keyword(s):  
Sea Level ◽  
Late Pleistocene ◽  
Gulf Stream ◽  
Climatic Variability ◽  
Atlantic Coast ◽  
High Amplitude ◽  
Climatic Conditions ◽  
Eastern United States ◽  
Sea Level Changes ◽  
Isthmus Of Panama

Marine climatic and sea-level changes in the eastern United States show two distinct modes: a gradual, directional Pliocene warming that ended with an abrupt regression, and a quasi-cyclic, high-amplitude, high-frequency middle-late Pleistocene pattern of alternating glacials and interglacials. Pliocene marine sediments of the Duplin Formation, deposited during a period of high sea level between 4.0 and 2.8 Ma BP, contain increasing percentages of tropical and subtropical ostracods, signifying a gradual warming. After maximum warm-water temperatures ca . 3.2-2.8 Ma BP, sea level dropped; this was followed by extensive subaerial erosion between about 2.8 and 2.0 Ma BP. This series of events reflects the emergence of the Isthmus of Panama between about 3.5 and 3.0 Ma BP, concomitant intensification of warm Gulf Stream flow along the eastern U.S.A., and initial Pliocene glaciation in the Northern Hemisphere. In the middle-late Pleistocene, glacial-interglacial cycles occurred with a periodicity of ca . 100 ka. Four (possibly five) emerged interglacial marine sequences correlate with deep-sea oxygen-isotope stages 13/11, 7, 5, and 1. During some interglacials, however, climatic conditions ranged from full interglacial warmth to cool, nearly interstadial conditions; this observation indicates short-term regional climatic variability.

scholarly journals Coastal Sea Level Trends from a Joint Use of Satellite Radar Altimetry, GPS and Tide Gauges: Case Study of the Northern Adriatic Sea

2021 ◽  
Author(s):  
Stefano Vignudelli ◽  
Francesco De Biasio
Keyword(s):  
Sea Level ◽  
Tide Gauges ◽  
Sea Level Changes ◽  
Northern Adriatic Sea ◽  
Radar Altimetry ◽  
Northern Adriatic ◽  
Coastal Sea ◽  
Satellite Radar ◽  
Along Track ◽  
Satellite Radar Altimetry

For the last century, tide gauges have been used to measure sea level change along the world’s coastline. However, tide gauges are heterogeneously distributed and sparse in coverage. The measured sea level changes are also affected by solid-Earth geophysics. Since 1992, satellite radar altimetry technique made possible to measure heights at sea independent of land changes. Recently various efforts started to improve the sea level record reprocessing past altimetry missions to create an almost 30 year-long combined record for sea level research studies. Moreover, coastal altimetry, i.e. the extension of altimetry into the oceanic coastal zone and its exploitation for looking at climate-scale variations of sea level, has had a steady progress in recent years and has become a recognized mission target for present and future satellite altimeters. Global sea level rise is today well acknowledged. On the opposite, the regional and local patterns are much more complicated to observe and explain. Sea level falls in some places and rises in others, as a consequence of natural cycles and anthropogenic causes. As relative sea level height continues to increase, many coastal cities can have the local elevation closer to the flooding line. It is evident that at land-sea interface a single technique is not enough to de-couple land and sea level changes. Satellite radar altimetry and tide gauges would coincide at coast if land had no vertical motion. By noting this fact, the difference of the two independent measurements is a proxy of land motion. In this chapter, we review recent advances in open ocean and coastal altimetry to measure sea level changes close to the coasts over the satellite radar altimetry era. The various methods to measure sea level trends are discussed, with focus on a more robust inverse method that has been tested in the Northern Adriatic Sea, where Global Positioning System (GPS) data are available to conduct a realistic assessment of uncertainties. The results show that the classical approach of estimating Vertical Land Motion (VLM) provides values that are almost half of those provided by the new Linear Inverse Problem With Constraints (LIPWC) method, in a new formulation which makes use of a change of variable (LIPWCCOV). Moreover, the accuracy of the new VLM estimates is lower when compared to the VLM estimated from GPS measurements. The experimental Sea Level Climate Change Initiative (SLCCI) data set (high resolution along track) coastal sea level product (developed within Climate Change Initiative (CCI project) that has been also assessed in the Gulf of Trieste show that the trends calculated with the gridded and along track datasets exhibit some differences, probably due to the different methodologies used in the generation of the products.

scholarly journals Global sea level reconstruction for 1900–2015 reveals regional variability in ocean dynamics and an unprecedented long weakening in the Gulf Stream flow since the 1990s

2020 ◽  
Author(s):  
Tal Ezer ◽  
Sonke Dangendorf
Keyword(s):  
Sea Level ◽  
Time Scales ◽  
Gulf Stream ◽  
Tide Gauge ◽  
Meridional Overturning Circulation ◽  
Ocean Dynamics ◽  
Regional Variability ◽  
Coastal Sea ◽  
Global Sea Level

Abstract. A new monthly global sea level reconstruction for 1900–2015 was analyzed and compared with various observations to examine regional variability and trends in the ocean dynamics of the western North Atlantic Ocean and the U.S. East Coast. A proxy of the Gulf Stream (GS) strength in the Mid-Atlantic Bight (GS-MAB) and in the South Atlantic Bight (GS-SAB) were derived from sea level differences across the GS in the two regions. While decadal oscillations dominate the 116-year record, the analysis showed an unprecedented long period of weakening in the GS flow since the late 1990s. The only other period of long weakening in the record was during the 1960s–1970s. Ensemble Empirical Mode Decomposition (EEMD) was used to separate oscillations at different time scales, showing that the low-frequency variability of the GS is connected to the Atlantic Multidecadal Oscillations (AMO) and the Atlantic Meridional Overturning Circulation (AMOC). The recent weakening of the reconstructed GS-MAB was mostly influenced by weakening of the upper mid-ocean transport component of AMOC as observed by the RAPID measurements for 2005–2015. Comparison between the reconstructed sea level near the coast and tide gauge data for 1927–2015 showed that the reconstruction underestimated observed coastal sea level variability for time scales less than ~ 5 years, but lower frequency variability of coastal sea level was captured very well in both amplitude and phase by the reconstruction. Comparison between the GS-SAB proxy and the observed Florida Current transport for 1982–2015 also showed significant correlations for oscillations with periods longer than ~ 5 years. The study demonstrated that despite the coarse horizontal resolution of the global reconstruction (1° x 1°), long-term variations in regional dynamics can be captured quite well, thus making the data useful for studies of long-term variability in other regions as well.

Coastal sea level change from Sentinel-3A SRAL over the U.S. Eastern seaboard

2021 ◽  
Author(s):  
Anrijs Abele ◽  
Sam Royston ◽  
Jonathan Bamber
Keyword(s):  
Sea Level ◽  
Spatial Scales ◽  
Atlantic Coast ◽  
Height Anomaly ◽  
Radar Altimeter ◽  
Sea Level Changes ◽  
Coastal Sea ◽  
Global Coverage ◽  
Sea Surface Height Anomaly

&lt;p&gt;Several satellite missions are planned or have been launched to contribute to our understanding of coastal oceanography and to observe sea level, a variable of high societal importance. One of those satellites is Sentinel-3A, which was launched in February 2016, giving near-global coverage at 27-day repeat cycle and carrying Ku- and C-band synthetic aperture radar altimeter (SRAL). SRAL has enabled more reliable remote sensing of coastal ocean sea level with a higher resolution than conventional altimetry. Here, the ability to robustly discern coherent sea level changes with Sentinel-3A SRAL products is evaluated at the oceanographically complex coastal regions of the Atlantic coast of North America.&lt;/p&gt;&lt;p&gt;We used RADS (Radar Altimeter Database System) L2 product to calculate sea surface height anomaly (SSHA) at a set of comparison points (CP)&amp;#8212;interpolating the measurements onto nominal ground tracks&amp;#8212;within 250 km around selected tide gauges (TG). We compared these CP with TG measurements and ECCO2 Cube92 model output to determine the correlations and obtain spatial scales and patterns of decorrelation between the SRAL observations and the other source of data (in situ and the model).&lt;/p&gt;

Multi-temporal Spaceborne InSAR technique to compensate Vertical Land Motion in Sea Level Change records: A case study of Tide gauges in Korean Peninsula

2020 ◽  
Author(s):  
Suresh Krishnan Palanisamy Vadivel ◽  
Duk-jin Kim ◽  
Jungkyo Jung ◽  
Yang-Ki Cho
Keyword(s):  
Sea Level ◽  
Ground Motion ◽  
Korean Peninsula ◽  
Ocean Dynamics ◽  
The Yellow Sea ◽  
Tide Gauges ◽  
Sea Level Changes ◽  
Vertical Land Motion ◽  
Multi Temporal ◽  
Sar Data

&lt;p&gt;Relative sea-level changes observed by tide gauges are commonly corrected for several components including crustal displacement, ocean dynamics, and vertical land motion. Vertical Land Motion (VLM) due to local land hydrology is a crucial component that observed as localized ground motion and varies with each tide gauges. Permanent GNSS stations are used to measure the VLM trend at tide gauges, however, only few tide gauges are equipped with collocated GNSS stations. Multi-temporal InSAR analysis provides ground displacements in both the spatial and temporal domains. Therefore, in our study, we applied the spaceborne Interferometric SAR technique to measure the local ground motion using Sentinel-1 SAR data. The Korean peninsula is surrounded by the East Sea/Sea of Japan, the Yellow Sea and the East China Sea have continuously monitoring tide gauges with a record length of more than 30 years. We acquire C-band Sentinel-1 SAR data (both ascending and descending mode) over the Korean Peninsula during 2014/11 and 2019/04. We estimate the high-resolution (~ 10 m) land motion at tide gauges (mm-level accuracy) over these 21 tide gauges and, compared with available collocated GNSS observations. 2D displacements (vertical and horizontal) are derived from ascending and descending mode InSAR displacements. The linear trend of VLM observed from our InSAR estimates is used to compensate for the relative velocity of sea-level changes observed from tide gauges.&lt;/p&gt;

scholarly journals On the Relationship between Synoptic Wintertime Atmospheric Variability and Path Shifts in the Gulf Stream and the Kuroshio Extension

2009 ◽  
Vol 22 (12) ◽  
pp. 3177-3192 ◽  
Author(s):  
Terrence M. Joyce ◽  
Young-Oh Kwon ◽  
Lisan Yu
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Gulf Stream ◽  
Kuroshio Extension ◽  
Storm Track ◽  
Western Boundary ◽  
Atmospheric Variability ◽  
The North ◽  
The Kuroshio ◽  
The North Pacific

Abstract Coherent, large-scale shifts in the paths of the Gulf Stream (GS) and the Kuroshio Extension (KE) occur on interannual to decadal time scales. Attention has usually been drawn to causes for these shifts in the overlying atmosphere, with some built-in delay of up to a few years resulting from propagation of wind-forced variability within the ocean. However, these shifts in the latitudes of separated western boundary currents can cause substantial changes in SST, which may influence the synoptic atmospheric variability with little or no time delay. Various measures of wintertime atmospheric variability in the synoptic band (2–8 days) are examined using a relatively new dataset for air–sea exchange [Objectively Analyzed Air–Sea Fluxes (OAFlux)] and subsurface temperature indices of the Gulf Stream and Kuroshio path that are insulated from direct air–sea exchange, and therefore are preferable to SST. Significant changes are found in the atmospheric variability following changes in the paths of these currents, sometimes in a local fashion such as meridional shifts in measures of local storm tracks, and sometimes in nonlocal, broad regions coincident with and downstream of the oceanic forcing. Differences between the North Pacific (KE) and North Atlantic (GS) may be partly related to the more zonal orientation of the KE and the stronger SST signals of the GS, but could also be due to differences in mean storm-track characteristics over the North Pacific and North Atlantic.

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