Deciphering forcing mechanisms for dynamic sea level variations off the northeast US coast

2020 ◽  
Author(s):  
Tong Lee ◽  
Ou Wang ◽  
Hong Zhang ◽  
Ian Fenty ◽  
ichiro fukumori
Keyword(s):  
Sea Level ◽  
Climate Models ◽  
Freshwater Flux ◽  
Level Variation ◽  
Sea Level Changes ◽  
Sea Level Variation ◽  
Regional Sea Level ◽  
Forcing Mechanisms ◽  
Northeast Us ◽  
Dynamic Sea Level

<p>Regional sea level change is strongly societal relevant. The knowledge about the forcing mechanisms for contemporary regional sea level variation is important to the evaluation of climate models and the fidelity of projected sea level changes using these models. Dynamic sea level variation off the northeast US coast has been a subject of significant interest of late. However, there is inadequate understanding about the forcing mechanisms and the underlying oceanic processes. The Estimating the Circulation and Climate of the Ocean (ECCO) state estimate reproduced well the observed interannual-to-decadal variation of dynamic sea level in the region during the satellite altimeter era. Here we use the ECCO adjoint sensitivity tools to quantify the relative contributions of local and remote winds, surface heat flux, and surface freshwater flux on dynamic sea level variation in this region. We further characterize the salient oceanic processes associated with different surface forcings on different time scales.</p>

scholarly journals Dynamic Sea Level Variation from GNSS: 2020 Shumagin Earthquake Tsunami Resonance and Hurricane Laura

2020 ◽  
Author(s):  
Kristine M. Larson ◽  
Thorne Lay ◽  
Yoshiki Yamazaki ◽  
Kwok Fai Cheung ◽  
Lingling Ye ◽  
...  
Keyword(s):  
Sea Level ◽  
Level Variation ◽  
Sea Level Variation ◽  
Dynamic Sea Level

scholarly journals Technical Note: Mean sea level variation in the Singapore Strait from long-term tide data

2012 ◽  
Vol 9 (3) ◽  
pp. 2255-2271
Author(s):  
P. Tkalich ◽  
M. T. Babu ◽  
P. Vethamony
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
El Niño ◽  
El Nino ◽  
Level Variation ◽  
Sea Level Changes ◽  
Mean Sea Level ◽  
Sea Level Variation ◽  
Singapore Strait

Abstract. Winds over the South China Sea (SCS) are primarily responsible for the observed variability in sea level anomalies (SLAs) in the Singapore Strait (SS). The present study focuses on remote forcing contributing to local mean sea level changes in the SS in seasonal and inter-annual scales, and relating the long term mean sea level variation to El Niño/ENSO. As Tanjong Pagar (TP) tide station in the SS has nearly 23.5 yr (1984–2007) of time series data with less data gaps, this data was subject to harmonic and sea level analyses. The mean sea level changes suggest that the fluctuations are quasi-periodic. Rising and falling of sea level is noticed atleast 7 times in a period of 15 yr, with 3 distinct sharp falls (1984–1987, 1989–1992 and 1995–1996) and 4 sharp rises (1987–1988, 1992–1993, 1994–1995 and 1997–1999). These sea level falls are related to El Niño events. When we segregated the results into 2 time spans, we find that from 1984 to 1999 the sea level was on the rising trend in spite of sharp falls, and from 1999 to 2007 on gradual falling trend. More or less similar trend was observed by other researchers for the SCS with altimetry data. During the El Niño periods of 1987 and 1992, the inter-annual MSL variability is the highest, of the order of 7 cm. In one of the events, sea level recovered from a fall of 60 mm (in 1987) to a rise of 40 mm (in 1988). During 1992 to 1999, sea level was continuously on rising trend (from −50 mm to +60 mm), except in one year (1995–1996). The analysis shows a MSL rise rate of 15.7 mm yr−1, which is very closer to MSL in the SCS. The average rate of sea level rise around Singapore as shown by the Tanjong Pagar tidal station is 1.6 mm yr−1, and this matches with the global sea level rise.

scholarly journals Evaluating Model Simulations of Twentieth-Century Sea-Level Rise. Part II: Regional Sea-Level Changes

2017 ◽  
Vol 30 (21) ◽  
pp. 8565-8593 ◽  
Author(s):  
B. Meyssignac ◽  
A. B. A Slangen ◽  
A. Melet ◽  
J. A. Church ◽  
X. Fettweis ◽  
...  
Keyword(s):  
Twentieth Century ◽  
Sea Level ◽  
Climate Models ◽  
Climate Model ◽  
Tide Gauge ◽  
Groundwater Depletion ◽  
Sea Level Changes ◽  
Tide Gauge Records ◽  
Model Simulations ◽  
Regional Sea Level

Twentieth-century regional sea level changes are estimated from 12 climate models from phase 5 of the Climate Model Intercomparison Project (CMIP5). The output of the CMIP5 climate model simulations was used to calculate the global and regional sea level changes associated with dynamic sea level, atmospheric loading, glacier mass changes, and ice sheet surface mass balance contributions. The contribution from groundwater depletion, reservoir storage, and dynamic ice sheet mass changes are estimated from observations as they are not simulated by climate models. All contributions are summed, including the glacial isostatic adjustment (GIA) contribution, and compared to observational estimates from 27 tide gauge records over the twentieth century (1900–2015). A general agreement is found between the simulated sea level and tide gauge records in terms of interannual to multidecadal variability over 1900–2015. But climate models tend to systematically underestimate the observed sea level trends, particularly in the first half of the twentieth century. The corrections based on attributable biases between observations and models that have been identified in Part I of this two-part paper result in an improved explanation of the spatial variability in observed sea level trends by climate models. Climate models show that the spatial variability in sea level trends observed by tide gauge records is dominated by the GIA contribution and the steric contribution over 1900–2015. Climate models also show that it is important to include all contributions to sea level changes as they cause significant local deviations; note, for example, the groundwater depletion around India, which is responsible for the low twentieth-century sea level rise in the region.

scholarly journals A Study on Regional Sea Level Variation Along the Indian Coast

2015 ◽  
Vol 116 ◽  
pp. 1078-1084 ◽  
Author(s):  
Piyali Chowdhury ◽  
Manasa Ranjan Behera
Keyword(s):  
Sea Level ◽  
Level Variation ◽  
Indian Coast ◽  
Sea Level Variation ◽  
Regional Sea Level

Intraseasonal Variability in the Persian Gulf Revealed by GRACE and Altimetry

2020 ◽  
Author(s):  
Christopher Piecuch ◽  
Rui Ponte ◽  
Ichiro Fukumori
Keyword(s):  
Indian Ocean ◽  
Sea Level ◽  
Persian Gulf ◽  
Large Scale ◽  
Freshwater Flux ◽  
Ocean Bottom ◽  
Level Variation ◽  
Gulf Of Oman ◽  
Sea Level Variation ◽  
The Persian Gulf

<p>The Persian Gulf is a semi-enclosed marginal sea of the Indian Ocean. It connects to the Arabian Sea through the Gulf of Oman and the Strait of Hormuz. The Persian Gulf has a large coastal population, and is relevant economically and geopolitically, and so it is important to understand sea-level changes in the region. We use satellite observations from the Gravity Recovery and Climate Experiment (<strong>GRACE</strong>) and satellite altimetry to study intraseasonal sea level variation over the Persian Gulf during 2002-2015. We interrogate the spatial scales and forcing functions of the variation and its relation to large-scale circulation and climate over the Indian Ocean. Empirical orthogonal function analysis applied to sea level data from satellite altimetry reveals that the intraseasonal sea level variation in the Persian Gulf is dominated by a basin-wide, single-signed mode of fluctuation. Maximum covariance analysis applied to altimetry and GRACE satellite retrievals shows that these basin-wide intraseasonal sea level fluctuations are largely barotropic in nature and coupled to variations in ocean bottom pressure. To interpret the results, we develop a simple linear barotropic theory based on volume and momentum conservation. The theory describes Persian Gulf sea level in terms of freshwater flux over the region, wind stress along the Strait of Hormuz, and sea level in the Gulf of Oman. To test this theory, we perform a complex multiple linear regression using these regional freshwater flux, wind stress, and sea level as inputs, and Persian Gulf sea level as output. The regression model explains ~70% of the intraseasonal Persian Gulf sea level variance. The magnitudes and phases of the coefficients determined from the regression model are consistent with expectations from the simple theory. The Gulf of Oman sea level boundary condition shows significant lagged correlation with intraseasonal sea level upstream along the Indian Subcontinent, Maritime Continent, and equatorial Indian Ocean. This hints at a large-scale circulation and climate influence on intraseasonal sea level variation of the Persian Gulf mediated by waves propagating along equatorial and coastal waveguides. This study highlights the value of GRACE retrievals of ocean bottom pressure for understanding sea level in an understudied semi-enclosed marginal sea.</p>

scholarly journals Reconciling global mean and regional sea level change in projections and observations

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jinping Wang ◽  
John A. Church ◽  
Xuebin Zhang ◽  
Xianyao Chen
Keyword(s):  
Sea Level ◽  
Climate Models ◽  
Tide Gauge ◽  
Sea Level Change ◽  
Global Network ◽  
Weighted Mean ◽  
Level Change ◽  
Regional Sea Level ◽  
Global Mean ◽  
Regional Sea Level Change

AbstractThe ability of climate models to simulate 20th century global mean sea level (GMSL) and regional sea-level change has been demonstrated. However, the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) and Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) sea-level projections have not been rigorously evaluated with observed GMSL and coastal sea level from a global network of tide gauges as the short overlapping period (2007–2018) and natural variability make the detection of trends and accelerations challenging. Here, we critically evaluate these projections with satellite and tide-gauge observations. The observed trends from GMSL and the regional weighted mean at tide-gauge stations confirm the projections under three Representative Concentration Pathway (RCP) scenarios within 90% confidence level during 2007–2018. The central values of the observed GMSL (1993–2018) and regional weighted mean (1970–2018) accelerations are larger than projections for RCP2.6 and lie between (or even above) those for RCP4.5 and RCP8.5 over 2007–2032, but are not yet statistically different from any scenario. While the confirmation of the projection trends gives us confidence in current understanding of near future sea-level change, it leaves open questions concerning late 21st century non-linear accelerations from ice-sheet contributions.

Projected sea-level changes in the marginal seas near China based on dynamical downscaling

2021 ◽  
pp. 1-52
Author(s):  
Yi Jin ◽  
Xuebin Zhang ◽  
John A. Church ◽  
Xianwen Bao
Keyword(s):  
Climate Change ◽  
Sea Level ◽  
Climate Models ◽  
Dynamical Downscaling ◽  
Global Climate Models ◽  
Open Boundary ◽  
Open Boundary Conditions ◽  
Sea Level Changes ◽  
Marginal Seas ◽  
The Pacific

AbstractProjections of future sea-level changes are usually based on global climate models (GCMs). However, the changes in shallow coastal regions, like the marginal seas near China, cannot be fully resolved in GCMs. To improve regional sea-level simulations, a high-resolution (~8 km) regional ocean model is set up for the marginal seas near China for both the historical (1994-2015) and future (2079-2100) periods under representative concentration pathways (RCPs) 4.5 and 8.5. The historical ocean simulations are evaluated at different spatiotemporal scales, and the model is then integrated for the future period, driven by projected monthly climatological climate change signals from 8 GCMs individually via both surface and open boundary conditions. The downscaled ocean changes derived by comparing historical and future experiments reveal greater spatial details than those from GCMs, e.g., a low dynamic sea level (DSL) centre of -0.15 m in the middle of the South China Sea (SCS). As a novel test, the downscaled results driven by the ensemble mean forcings are almost identical with the ensemble average results from individually downscaled cases. Forcing of the DSL change and increased cyclonic circulation in the SCS are dominated by the climate change signals from the Pacific, while the DSL change in the East China marginal seas is caused by both local atmosphere forcing and signals from the Pacific. The method of downscaling developed in this study is a useful modelling protocol for adaptation and mitigation planning for future oceanic climate changes.

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