scholarly journals Can We Resolve the Basin‐Scale Sea Level Trend Budget From GRACE Ocean Mass?

2020 ◽  
Vol 125 (1) ◽  
Author(s):  
Sam Royston ◽  
Bramha Dutt Vishwakarma ◽  
Richard Westaway ◽  
Jonathan Rougier ◽  
Zhe Sha ◽  
...  
Keyword(s):  
Sea Level ◽  
Ocean Mass ◽  
Basin Scale ◽  
Sea Level Trend

scholarly journals Sea Level Trend and Fronts in the South Atlantic Ocean

Geosciences ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 218
Author(s):  
Laura A. Ruiz-Etcheverry ◽  
Martin Saraceno
Keyword(s):  
Atlantic Ocean ◽  
Sea Level ◽  
Satellite Altimetry ◽  
South Atlantic ◽  
South Atlantic Ocean ◽  
The South ◽  
Steric Height ◽  
Ocean Mass ◽  
Sea Level Trend ◽  
Height Component

The understanding of the physical drivers of sea level trend is crucial on global and regional scales. In particular, little is known about the sea level trend in the South Atlantic Ocean in comparison with other parts of the world. In this work, we computed the South Atlantic mean sea level (SAMSL) trend from 25 years of satellite altimetry data, and we analyzed the contributions of steric height (thermosteric and halosteric components) and ocean mass changes for the period 2005–2016 when all the source data used (Argo, GRACE and satellite altimetry) overlap. The SAMSL trend is 2.65 ± 0.24 mm/yr and is mostly explained by ocean mass trend, which is 2.22 ± 0.21 mm/yr. However, between 50° S–33° S, the steric height component constitutes the main contribution in comparison with the ocean mass component. Within that latitudinal band, three regions with trend values higher than the SAMSL trend are observed when considering 25 years of satellite SLA. In the three regions, a southward displacement of the Subtropical, Subantarctic, and Polar Fronts is observed. The southward shift of the fronts is associated with the strengthening and polar shift of westerly winds and contributes to a clear thermosteric trend that translates to the SLA trend observed in those regions.

scholarly journals Interdecadal Baroclinic Sea Level Changes in the North Pacific Based on Historical Ocean Hydrographic Observations

2015 ◽  
Vol 28 (11) ◽  
pp. 4585-4594 ◽  
Author(s):  
Tatsuo Suzuki ◽  
Masayoshi Ishii
Keyword(s):  
Sea Level ◽  
Wind Stress ◽  
North Pacific ◽  
Water Mass ◽  
Mass Density ◽  
Baroclinic Mode ◽  
Sea Level Changes ◽  
The North ◽  
Basin Scale ◽  
The North Pacific

Abstract Using historical ocean hydrographic observations, decadal to multidecadal sea level changes from 1951 to 2007 in the North Pacific were investigated focusing on vertical density structures. Hydrographically, the sea level changes could reflect the following: changes in the depth of the main pycnocline, density gradient changes across the pycnocline, and modification of the water mass density structure within the pycnocline. The first two processes are characterized as the first baroclinic mode. The changes in density stratification across the pycnocline are sufficiently small to maintain the vertical profile of the first baroclinic mode in this analysis period. Therefore, the first mode should represent mainly the dynamical response to the wind stress forcing. Meanwhile, changes in the composite of all modes of order greater than 1 (remaining baroclinic mode) can be attributed to water mass modifications above the pycnocline. The first baroclinic mode is associated with 40–60-yr fluctuations in the subtropical gyre and bidecadal fluctuations of the Kuroshio Extension (KE) in response to basin-scale wind stress changes. In addition to this, the remaining baroclinic mode exhibits strong variability around the recirculation region south of the KE and regions downstream of the KE, accompanied by 40–60-yr and bidecadal fluctuations, respectively. These fluctuations follow spinup/spindown of the subtropical gyre and meridional shifts of the KE shown in the first mode, respectively. A lag correlation analysis suggests that interdecadal sea level changes due to water mass density changes are a secondary consequence of changes in basin-scale wind stress forcing related to the ocean circulation changes associated with the first mode.

Holocene sea level trend on the west coast of Bohai Bay, China: reanalysis and standardization

2021 ◽  
Vol 40 (7) ◽  
pp. 198-248
Author(s):  
Jianfen Li ◽  
Zhiwen Shang ◽  
Fu Wang ◽  
Yongsheng Chen ◽  
Lizhu Tian ◽  
...  
Keyword(s):  
Sea Level ◽  
West Coast ◽  
Bohai Bay ◽  
The West ◽  
Sea Level Trend ◽  
Holocene Sea Level

scholarly journals Impacts of Basin-Scale Climate Modes on Coastal Sea Level: a Review

2019 ◽  
Vol 40 (6) ◽  
pp. 1493-1541 ◽  
Author(s):  
Weiqing Han ◽  
Detlef Stammer ◽  
Philip Thompson ◽  
Tal Ezer ◽  
Hindu Palanisamy ◽  
...  
Keyword(s):  
Sea Level ◽  
Climate Modes ◽  
Basin Scale ◽  
Coastal Sea

scholarly journals Tropical Pacific spatial trend patterns in observed sea level: internal variability and/or anthropogenic signature?

2012 ◽  
Vol 8 (2) ◽  
pp. 787-802 ◽  
Author(s):  
B. Meyssignac ◽  
D. Salas y Melia ◽  
M. Becker ◽  
W. Llovel ◽  
A. Cazenave
Keyword(s):  
Sea Level ◽  
Climate Models ◽  
Internal Variability ◽  
Tropical Pacific ◽  
External Forcing ◽  
Spatial Trend ◽  
Trend Pattern ◽  
Coupled Climate Models ◽  
Sea Level Trend ◽  
The Tropical Pacific

Abstract. In this study we focus on the sea level trend pattern observed by satellite altimetry in the tropical Pacific over the 1993–2009 time span (i.e. 17 yr). Our objective is to investigate whether this 17-yr-long trend pattern was different before the altimetry era, what was its spatio-temporal variability and what have been its main drivers. We try to discriminate the respective roles of the internal variability of the climate system and of external forcing factors, in particular anthropogenic emissions (greenhouse gases and aerosols). On the basis of a 2-D past sea level reconstruction over 1950–2009 (based on a combination of observations and ocean modelling) and multi-century control runs (i.e. with constant, preindustrial external forcing) from eight coupled climate models, we have investigated how the observed 17-yr sea level trend pattern evolved during the last decades and centuries, and try to estimate the characteristic time scales of its variability. For that purpose, we have computed sea level trend patterns over successive 17-yr windows (i.e. the length of the altimetry record), both for the 60-yr long reconstructed sea level and the model runs. We find that the 2-D sea level reconstruction shows spatial trend patterns similar to the one observed during the altimetry era. The pattern appears to have fluctuated with time with a characteristic time scale of the order of 25–30 yr. The same behaviour is found in multi-centennial control runs of the coupled climate models. A similar analysis is performed with 20th century coupled climate model runs with complete external forcing (i.e. solar plus volcanic variability and changes in anthropogenic forcing). Results suggest that in the tropical Pacific, sea level trend fluctuations are dominated by the internal variability of the ocean–atmosphere coupled system. While our analysis cannot rule out any influence of anthropogenic forcing, it concludes that the latter effect in that particular region is stillhardly detectable.

scholarly journals Assessment of the Greenland ice sheet–atmosphere feedbacks for the next century with a regional atmospheric model coupled to an ice sheet model

2019 ◽  
Vol 13 (1) ◽  
pp. 373-395 ◽  
Author(s):  
Sébastien Le clec'h ◽  
Sylvie Charbit ◽  
Aurélien Quiquet ◽  
Xavier Fettweis ◽  
Christophe Dumas ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Atmospheric Model ◽  
Ice Dynamics ◽  
Surface Slopes ◽  
Regional Atmospheric Model ◽  
Basin Scale ◽  
Coupling Strategies

Abstract. In the context of global warming, growing attention is paid to the evolution of the Greenland ice sheet (GrIS) and its contribution to sea-level rise at the centennial timescale. Atmosphere–GrIS interactions, such as the temperature–elevation and the albedo feedbacks, have the potential to modify the surface energy balance and thus to impact the GrIS surface mass balance (SMB). In turn, changes in the geometrical features of the ice sheet may alter both the climate and the ice dynamics governing the ice sheet evolution. However, changes in ice sheet geometry are generally not explicitly accounted for when simulating atmospheric changes over the Greenland ice sheet in the future. To account for ice sheet–climate interactions, we developed the first two-way synchronously coupled model between a regional atmospheric model (MAR) and a 3-D ice sheet model (GRISLI). Using this novel model, we simulate the ice sheet evolution from 2000 to 2150 under a prolonged representative concentration pathway scenario, RCP8.5. Changes in surface elevation and ice sheet extent simulated by GRISLI have a direct impact on the climate simulated by MAR. They are fed to MAR from 2020 onwards, i.e. when changes in SMB produce significant topography changes in GRISLI. We further assess the importance of the atmosphere–ice sheet feedbacks through the comparison of the two-way coupled experiment with two other simulations based on simpler coupling strategies: (i) a one-way coupling with no consideration of any change in ice sheet geometry; (ii) an alternative one-way coupling in which the elevation change feedbacks are parameterized in the ice sheet model (from 2020 onwards) without taking into account the changes in ice sheet topography in the atmospheric model. The two-way coupled experiment simulates an important increase in surface melt below 2000 m of elevation, resulting in an important SMB reduction in 2150 and a shift of the equilibrium line towards elevations as high as 2500 m, despite a slight increase in SMB over the central plateau due to enhanced snowfall. In relation with these SMB changes, modifications of ice sheet geometry favour ice flux convergence towards the margins, with an increase in ice velocities in the GrIS interior due to increased surface slopes and a decrease in ice velocities at the margins due to decreasing ice thickness. This convergence counteracts the SMB signal in these areas. In the two-way coupling, the SMB is also influenced by changes in fine-scale atmospheric dynamical processes, such as the increase in katabatic winds from central to marginal regions induced by increased surface slopes. Altogether, the GrIS contribution to sea-level rise, inferred from variations in ice volume above floatation, is equal to 20.4 cm in 2150. The comparison between the coupled and the two uncoupled experiments suggests that the effect of the different feedbacks is amplified over time with the most important feedbacks being the SMB–elevation feedbacks. As a result, the experiment with parameterized SMB–elevation feedback provides a sea-level contribution from GrIS in 2150 only 2.5 % lower than the two-way coupled experiment, while the experiment with no feedback is 9.3 % lower. The change in the ablation area in the two-way coupled experiment is much larger than those provided by the two simplest methods, with an underestimation of 11.7 % (14 %) with parameterized feedbacks (no feedback). In addition, we quantify that computing the GrIS contribution to sea-level rise from SMB changes only over a fixed ice sheet mask leads to an overestimation of ice loss of at least 6 % compared to the use of a time variable ice sheet mask. Finally, our results suggest that ice-loss estimations diverge when using the different coupling strategies, with differences from the two-way method becoming significant at the end of the 21st century. In particular, even if averaged over the whole GrIS the climatic and ice sheet fields are relatively similar; at the local and regional scale there are important differences, highlighting the importance of correctly representing the interactions when interested in basin scale changes.

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