Coherent Coastal Sea-Level Variability at Interdecadal and Interannual Scales from Tide Gauges

Validation of the ALES Coastal Altimetry Dataset against the Norwegian Tide Gauges

10.5194/egusphere-egu21-14596 ◽

2021 ◽

Author(s):

Fabio Mangini ◽

Antonio Bonaduce ◽

Léon Chafik ◽

Laurent Bertino

Keyword(s):

Sea Level ◽

Satellite Altimetry ◽

Tide Gauge ◽

Linear Trend ◽

Tide Gauges ◽

Sea Level Variability ◽

Preliminary Results ◽

In Situ Data ◽

Coastal Sea

<p>Satellite altimetry measurements, complemented by in-situ records, have made a fundamental contribution to the understanding of global sea level variability for almost 30 years. Due to land contamination, it performs best over the open ocean. However, over the years, there has been a significant effort to improve the altimetry products in coastal regions. Indeed, altimetry observations could be fruitfully used in the coastal zone to complement the existing tide gauge network which, despite its relevance, does not represent the entire coast.&#160;Given the important role of coastal altimetry in oceanography, we have recently decided to check the quality of a new coastal altimetry dataset, ALES, along the coast of Norway. The Norwegian coast is well covered by tide gauges and, therefore, particularly suitable to validate a coastal altimetry dataset. Preliminary results show a good agreement between in-situ and remote sensing sea-level signals in terms of linear trend, seasonal cycle and inter-annual variability. For example, the linear correlation coefficient between the inter-annual sea level variability from altimetry and tide gauges exceeds 0.8. Likewise, the root mean square difference between the two is less than 2 cm at most tide gauge locations. A comparison with Breili et al. (2017) shows that ALES performs better than the standard satellite altimetry products at estimating sea level trends along the coast of Norway. Notably, in the Lofoten region, the difference between the sea level trends computed using ALES and the tide gauges range between 0.0 to 0.7 mm/year, compared to circa 1 to 3 mm/year found by Breili et al. (2017). These preliminary results go in the direction of obtaining an accurate characterization of coastal sea-level at the high latitudes based on coastal altimetry records, which can represent a valuable source of information to reconstruct coastal sea-level signals in areas where in-situ data are missing or inaccurate.</p>

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Sea-level variability and change along the Norwegian coast between 2003 and 2018 from satellite altimetry, tide gauges and hydrography

10.5194/os-2021-55 ◽

2021 ◽

Author(s):

Fabio Mangini ◽

Léon Chafik ◽

Antonio Bonaduce ◽

Laurent Bertino ◽

Jan Even Øie Nilsen

Keyword(s):

Sea Level ◽

Annual Cycle ◽

Satellite Altimetry ◽

Tide Gauges ◽

Sea Level Anomaly ◽

Sea Level Variability ◽

Norwegian Coast ◽

Coastal Sea ◽

Sea Level Variations ◽

Sea Level Trend

Abstract. Sea-level variations in coastal areas can differ significantly from those in the nearby open ocean. Monitoring coastal sea-level variations is therefore crucial to understand how climate variability can affect the densely populated coastal regions of the globe. In this paper, we study the sea-level variability along the coast of Norway by means of in situ records, satellite altimetry data, and a network of eight hydrographic stations over a period spanning 16 years (from 2003 to 2018). At first, we evaluate the performance of the ALES-reprocessed coastal altimetry dataset by comparing it with the sea-level anomaly from tide gauges over a range of timescales, which include the long-term trend, the annual cycle and the detrended and deseasoned sea level anomaly. We find that coastal altimetry outperforms conventional altimetry products at most locations along the Norwegian coast. We later take advantage of the coastal altimetry dataset to perform a sea level budget along the Norwegian coast. We find that the thermosteric and the halosteric signals give a comparable contribution to the sea-level trend along the Norwegian coast, except for three, non-adjacent hydrographic stations, where salinity variations affect the sea-level trend more than temperature variations. We also find that the sea-level annual cycle is more affected by variations in temperature than in salinity, and that both temperature and salinity give a comparable contribution to the detrended and deseasoned sea-level along the entire Norwegian coast.

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Long-Term Changes, Inter-Annual, and Monthly Variability of Sea Level at the Coasts of the Spanish Mediterranean and the Gulf of Cádiz

Geosciences ◽

10.3390/geosciences11080350 ◽

2021 ◽

Vol 11 (8) ◽

pp. 350

Author(s):

Manuel Vargas-Yáñez ◽

Elena Tel ◽

Francina Moya ◽

Enrique Ballesteros ◽

Mari Carmen García-Martínez

Keyword(s):

Sea Level ◽

Linear Models ◽

Numerical Models ◽

Eastern Mediterranean ◽

Tide Gauges ◽

Atmospheric Forcing ◽

Contributing Factors ◽

Sea Level Variability ◽

Coastal Sea

One of the effects of climate change is the rise of sea level, which poses an important threat to coastal areas. Therefore, the protection and management of coastal ecosystems as well as human infrastructures and constructions require an accurate knowledge of those changes occurring at a local scale. In this study, long time series of sea level from tide gauges distributed along the southern (Atlantic) and eastern (Mediterranean) Spanish coasts were analyzed. Linear trends were calculated for two periods, from early 1940s to 2018 and from 1990 to 2018. Values for the former period ranged between 0.68 and 1.22 mm/year. These trends experienced a significant increase for the second period, when they ranged between 1.5 and 4.6 mm/year. Previous research analyzed the effect of atmospheric forcing in the Mediterranean Sea by means of 2D numerical models, and the steric contribution was directly evaluated by the integration of density along the water column. In this study, the effect of atmospheric forcing and the thermosteric and halosteric contributions on coastal sea level were empirically determined by means of statistical linear models that established which factors affected sea level at each location and what the numerical response of the observed sea level was to the contributing factors. Atmospheric pressure and the west–east component of the wind hada significant contribution to the sea level variability at most of the tide gauges. The thermosteric and halosteric components of sea level also contributed to the sea level variability at all the tide gauges, with the only exception of Alicante. Atmospheric forcing and the steric components of sea level experienced long-term trends. The combination of such trends, with the response of sea level to these factors, allowed us to estimate their contribution to the observed sea level trends. The part of these trends not explained by the atmospheric variables and the steric contributions was attributed to mass addition. Trends associated with mass addition ranged between 0.6 and 1.2 mm/year for the period 1948–2018 and between 1.0 and 4.5 mm/year for the period 1990–2018.

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Coastal sea level variability in the Bohai Bay: influence of atmospheric forcing and prediction

Journal of Oceanology and Limnology ◽

10.1007/s00343-019-7383-y ◽

2018 ◽

Vol 37 (2) ◽

pp. 486-497 ◽

Cited By ~ 1

Author(s):

Xianqing Lü ◽

Daosheng Wang ◽

Bing Yan ◽

Hua Yang

Keyword(s):

Sea Level ◽

Bohai Bay ◽

Atmospheric Forcing ◽

Sea Level Variability ◽

Coastal Sea

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Atmospheric circulation changes and their impact on extreme sea levels around Australia

Natural Hazards and Earth System Science ◽

10.5194/nhess-19-1067-2019 ◽

2019 ◽

Vol 19 (5) ◽

pp. 1067-1086 ◽

Cited By ~ 4

Author(s):

Frank Colberg ◽

Kathleen L. McInnes ◽

Julian O'Grady ◽

Ron Hoeke

Keyword(s):

Sea Level ◽

Large Scale ◽

Climate Models ◽

Tide Gauge ◽

Austral Summer ◽

Sea Level Changes ◽

Sea Level Variability ◽

Sea Levels ◽

Extreme Sea Levels ◽

Coastal Sea

Abstract. Projections of sea level rise (SLR) will lead to increasing coastal impacts during extreme sea level events globally; however, there is significant uncertainty around short-term coastal sea level variability and the attendant frequency and severity of extreme sea level events. In this study, we investigate drivers of coastal sea level variability (including extremes) around Australia by means of historical conditions as well as future changes under a high greenhouse gas emissions scenario (RCP 8.5). To do this, a multi-decade hindcast simulation is validated against tide gauge data. The role of tide–surge interaction is assessed and found to have negligible effects on storm surge characteristic heights over most of the coastline. For future projections, 20-year-long simulations are carried out over the time periods 1981–1999 and 2081–2099 using atmospheric forcing from four CMIP5 climate models. Changes in extreme sea levels are apparent, but there are large inter-model differences. On the southern mainland coast all models simulated a southward movement of the subtropical ridge which led to a small reduction in sea level extremes in the hydrodynamic simulations. Sea level changes over the Gulf of Carpentaria in the north are largest and positive during austral summer in two out of the four models. In these models, changes to the northwest monsoon appear to be the cause of the sea level response. These simulations highlight a sensitivity of this semi-enclosed gulf to changes in large-scale dynamics in this region and indicate that further assessment of the potential changes to the northwest monsoon in a larger multi-model ensemble should be investigated, together with the northwest monsoon's effect on extreme sea levels.

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Sea level variability and trends in the Adriatic Sea in 1993–2008 from tide gauges and satellite altimetry

Physics and Chemistry of the Earth Parts A/B/C ◽

10.1016/j.pce.2011.05.014 ◽

2012 ◽

Vol 40-41 ◽

pp. 47-58 ◽

Cited By ~ 22

Author(s):

Luciana Fenoglio-Marc ◽

Carla Braitenberg ◽

Lavinia Tunini

Keyword(s):

Sea Level ◽

Satellite Altimetry ◽

Adriatic Sea ◽

Tide Gauges ◽

Sea Level Variability

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Atmospheric Circulation Changes and their Impact on Extreme Sea Levels around Australia

10.5194/nhess-2018-64 ◽

2018 ◽

Author(s):

Frank Colberg ◽

Kathleen L. McInnes ◽

Julian O'Grady ◽

Ron K. Hoeke

Keyword(s):

Sea Level ◽

Atmospheric Circulation ◽

Climate Models ◽

Tide Gauge ◽

Austral Summer ◽

Sea Level Variability ◽

Sea Levels ◽

Extreme Sea Levels ◽

Coastal Sea ◽

Circulation Changes

Abstract. Projections of sea level rise (SLR) will lead to increasing coastal impacts during extreme sea level events globally, however, there is significant uncertainty around short-term coastal sea level variability and the attendant frequency and severity of extreme sea level events. In this study, we investigate drivers of coastal sea level variability (including extremes) around Australia by means of historical conditions as well as future changes under a high greenhouse gas emissions scenario (RCP8.5). To do this, a multi-decade hindcast simulation is validated against tide gauge data. The role of tide-surge interaction is assessed and found to have negligible effects on storm surge characteristic heights over most of the coastline. For future projections, twenty-year long simulations are carried out over the time periods 1981–1999 and 2081–2099 using atmospheric forcing from four CMIP5 climate models. Results provide insights into how future atmospheric circulation changes may impact Australia's coastal zone and highlight regions of potential sensitivity to atmospheric circulation changes. Areas of note are the Gulf of Carpentaria in the north where changes to the northwest monsoon could lead to relatively large increases in extreme sea levels during Austral summer. For the southern mainland coast the simulated scenarios suggest that a southward movement of the subtropical ridge leads to a small reduction in sea level extremes.

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The zone of influence: matching sea level variability from coastal altimetry and tide gauges for vertical land motion estimation

Ocean Science ◽

10.5194/os-17-35-2021 ◽

2021 ◽

Vol 17 (1) ◽

pp. 35-57

Author(s):

Julius Oelsmann ◽

Marcello Passaro ◽

Denise Dettmering ◽

Christian Schwatke ◽

Laura Sánchez ◽

...

Keyword(s):

Sea Level ◽

Spatial Scales ◽

Tide Gauges ◽

Sea Level Changes ◽

Relative Sea Level ◽

Sea Level Variability ◽

Vertical Land Motion ◽

Spatial Coverage ◽

Coupling Procedure ◽

Zone Of Influence

Abstract. Vertical land motion (VLM) at the coast is a substantial contributor to relative sea level change. In this work, we present a refined method for its determination, which is based on the combination of absolute satellite altimetry (SAT) sea level measurements and relative sea level changes recorded by tide gauges (TGs). These measurements complement VLM estimates from the GNSS (Global Navigation Satellite System) by increasing their spatial coverage. Trend estimates from the SAT and TG combination are particularly sensitive to the quality and resolution of applied altimetry data as well as to the coupling procedure of altimetry and TGs. Hence, a multi-mission, dedicated coastal along-track altimetry dataset is coupled with high-frequency TG measurements at 58 stations. To improve the coupling procedure, a so-called “zone of influence” (ZOI) is defined, which confines coherent zones of sea level variability on the basis of relative levels of comparability between TG and altimetry observations. Selecting 20 % of the most representative absolute sea level observations in a 300 km radius around the TGs results in the best VLM estimates in terms of accuracy and uncertainty. At this threshold, VLMSAT-TG estimates have median formal uncertainties of 0.58 mm yr−1. Validation against GNSS VLM estimates yields a root mean square (rmsΔVLM) of VLMSAT-TG and VLMGNSS differences of 1.28 mm yr−1, demonstrating the level of accuracy of our approach. Compared to a reference 250 km radius selection, the 300 km zone of influence improves trend accuracies by 15 % and uncertainties by 35 %. With increasing record lengths, the spatial scales of the coherency in coastal sea level trends increase. Therefore, the relevance of the ZOI for improving VLMSAT-TG accuracy decreases. Further individual zone of influence adaptations offer the prospect of bringing the accuracy of the estimates below 1 mm yr−1.

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