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 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.

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 Uncertainties in Long-Term Twenty-First Century Process-Based Coastal Sea-Level Projections

2019 ◽  
Vol 40 (6) ◽  
pp. 1655-1671 ◽  
Author(s):  
R. S. W. van de Wal ◽  
X. Zhang ◽  
S. Minobe ◽  
S. Jevrejeva ◽  
R. E. M. Riva ◽  
...  
Keyword(s):  
Sea Level ◽  
First Century ◽  
Spatial And Temporal Scales ◽  
Level Change ◽  
Geographical Variations ◽  
Ocean Response ◽  
Coastal Sea ◽  
Geophysical Processes ◽  
Global Sea Level

Abstract Many processes affect sea level near the coast. In this paper, we discuss the major uncertainties in coastal sea-level projections from a process-based perspective, at different spatial and temporal scales, and provide an outlook on how these uncertainties may be reduced. Uncertainty in centennial global sea-level rise is dominated by the ice sheet contributions. Geographical variations in projected sea-level change arise mainly from dynamical patterns in the ocean response and other geophysical processes. Finally, the uncertainties in the short-duration extreme sea-level events are controlled by near coastal processes, storms and tides.

scholarly journals Sea level: measuring the bounding surfaces of the ocean

2014 ◽  
Vol 372 (2025) ◽  
pp. 20130336 ◽  
Author(s):  
Mark E. Tamisiea ◽  
Chris W. Hughes ◽  
Simon D. P. Williams ◽  
Richard M. Bingley
Keyword(s):  
Sea Level ◽  
Tide Gauge ◽  
Safe Navigation ◽  
Scientific Disciplines ◽  
Observation Systems ◽  
Global Sea Level ◽  
Geological Constraints ◽  
Bounding Surfaces

The practical need to understand sea level along the coasts, such as for safe navigation given the spatially variable tides, has resulted in tide gauge observations having the distinction of being some of the longest instrumental ocean records. Archives of these records, along with geological constraints, have allowed us to identify the century-scale rise in global sea level. Additional data sources, particularly satellite altimetry missions, have helped us to better identify the rates and causes of sea-level rise and the mechanisms leading to spatial variability in the observed rates. Analysis of all of the data reveals the need for long-term and stable observation systems to assess accurately the regional changes as well as to improve our ability to estimate future changes in sea level. While information from many scientific disciplines is needed to understand sea-level change, this review focuses on contributions from geodesy and the role of the ocean's bounding surfaces: the sea surface and the Earth's crust.

scholarly journals Inferring regional vertical crustal velocities from averaged relative sea level trends: A proof of concept

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
H. Bâki Iz ◽  
C. K. Shum ◽  
C. Zhang ◽  
C. Y. Kuo
Keyword(s):  
Sea Level ◽  
Tide Gauge ◽  
Eastern Coast ◽  
Adjustment Process ◽  
Tide Gauge Records ◽  
Relative Sea Level ◽  
Isostatic Adjustment ◽  
Vertical Crustal Motion ◽  
Gps Time Series

AbstractThis study demonstrates that relative sea level trends calculated from long-term tide gauge records can be used to estimate relative vertical crustal velocities in a region with high accuracy. A comparison of the weighted averages of the relative sea level trends estimated at six tide gauge stations in two clusters along the Eastern coast of United States, in Florida and in Maryland, reveals a statistically significant regional vertical crustal motion of Maryland with respect to Florida with a subsidence rate of −1.15±0.15 mm/yr identified predominantly due to the ongoing glacial isostatic adjustment process. The estimate is a consilience value to validate vertical crustal velocities calculated from GPS time series as well as towards constraining predictive GIA models in these regions.

Mean Sea Level as a Reference for Geodetic Leveling

1974 ◽  
Vol 28 (5) ◽  
pp. 524-530 ◽  
Author(s):  
G. W. Lennon
Keyword(s):  
Sea Level ◽  
World Ocean ◽  
Equipotential Surface ◽  
Scientific Discipline ◽  
Mean Sea Level ◽  
Sea Levels ◽  
Coastal Sea ◽  
Long Time ◽  
Marine System

The use of mean sea level as a surface of reference that might provide an independent control for geodetic leveling has been a long term goal arising from the classical analogy between the geoid as an equipotential surface and the surface assumed by a hypothetical undisturbed world ocean. The problems associated with this aim are now known to be vast, and are associated with the dynamics of the marine system, notably its response to meteorological forces, to variations in density and to the effects of basic circulation patterns. In consequence the mean sea level surface varies rapidly in both time and space. This identifies in fact a distinctive scientific discipline, coastal geodesy, in which contributions are required by both geodesists and oceanographers. It has come to be recognized that the coastal zone is a hazardous environment for all observational techniques concerned. On the one hand, the difficulties of measurement of coastal sea levels have only recently been understood; on the other hand, precise leveling procedures are now known to be influenced by the attraction of marine tides and by crustal deformation of tidal loading. Much of the data available for study are therefore inadequate and, moreover, it should be noted that long-time series are required. It is now possible to lay plans for both geodetic and oceanographic procedures to remedy these deficiencies in the long-term interests of the study.

Periodically forced self-organization in the long-term evolution of planktic foraminifera

2001 ◽  
Vol 38 (2) ◽  
pp. 293-308 ◽  
Author(s):  
Andreas Prokoph ◽  
Anthony D Fowler ◽  
R Timothy Patterson
Keyword(s):  
Sea Level ◽  
Logistic Map ◽  
Late Eocene ◽  
Self Organization ◽  
Extinction Data ◽  
Sea Level Fluctuations ◽  
Global Sea Level ◽  
Extinction Events ◽  
The Impact

Wavelet transform and other signal analysis techniques suggest that the planktic foraminiferal (PF) long-term evolutionary record of the last 127 Ma can be attributed to complex periodic and nonlinear patterns. Correlation of the PF extinction pattern with other geological series favors an origin of the ~30 Ma periodicity and self-organization by quasi-periodic mantle-plume cycles that in turn drive episodic volcanism, CO2-degassing, oceanic anoxic conditions, and sea-level fluctuations. Stationary ~30 Ma periodicity and a weak secular trend of ~100 Ma period are evident in the PF record, even without consideration of the mass extinction at the K–T boundary. The 27–32 Ma periodicity in the impact crater record and lows in the global sea-level curve, respectively, are ~6.5 Ma and ~2.3 Ma out of phase with PF-extinction data, although major PF-extinction events correspond to the bolide impacts at the K–T boundary and in late Eocene. Another six extinction events correspond to abrupt global sea-level falls between the late Albian and early Oligocene. Self-organization in the PF record is characterized by increased radiation rates after major extinction events and a steady number of baseline species. Our computer model of long-term PF evolution replicates this SO pattern. The model consists of output from the logistic map, which is forced at 30 Ma and 100 Ma frequencies. The model has significant correlations with the relative PF-extinction data. In particular, it replicates singularities, such as the K–T event, nonstationary 2.5–10 Ma periodicities, and phase shifts in the ~30 Ma periodicity of the PF record.

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