scholarly journals Crustal uplift and sea level rise in northern Cascadia from GPS, absolute gravity, and tide gauge data

2007 ◽  
Vol 34 (15) ◽  
Author(s):  
S. Mazzotti ◽  
A. Lambert ◽  
N. Courtier ◽  
L. Nykolaishen ◽  
H. Dragert
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Tide Gauge ◽  
Absolute Gravity ◽  
Tide Gauge Data ◽  
Gauge Data ◽  
Crustal Uplift ◽  
And Sea Level

scholarly journals Measuring rates of present-day relative sea-level rise in low-elevation coastal zones: A critical evaluation

2018 ◽  
Author(s):  
Molly E. Keogh ◽  
Torbjörn E. Törnqvist
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Land Surface ◽  
Tide Gauge ◽  
Tide Gauges ◽  
Coastal Zones ◽  
Tide Gauge Data ◽  
Relative Sea Level ◽  
Gauge Data ◽  
Coastal Louisiana

Abstract. Although tide gauges are the primary source of data used to calculate multi-decadal to century-scale rates of relative sea-level change, we question the reliability of tide-gauge data in rapidly subsiding low-elevation coastal zones (LECZs). Tide gauges measure relative sea-level rise (RSLR) with respect to the base of associated benchmarks. Focusing on coastal Louisiana, the largest LECZ in the United States, we find that these benchmarks (n = 35) are anchored an average of 21.5 m below the land surface. Because at least 60 % of subsidence occurs in the top 5–10 m of the sediment column in this area, tide gauges in coastal Louisiana do not capture the primary contributor to RSLR. Similarly, GPS stations (n = 10) are anchored an average of > 14.3 m below the land surface and therefore also do not capture shallow subsidence. As a result, tide gauges and GPS stations in coastal Louisiana, and likely in LECZs worldwide, systematically underestimate rates of RSLR as experienced at the land surface. We present an alternative approach that explicitly measures RSLR in LECZs with respect to the land surface and eliminates the need for tide-gauge data. Shallow subsidence is measured by rod surface-elevation table‒marker horizons (RSET-MHs) and added to measurements of deep subsidence from GPS data, plus sea-level rise from satellite altimetry. We show that for a LECZ the size of coastal Louisiana (25,000–30,000 km2), about 40 RSET-MH instruments suffice to collect useful data. Rates of RSLR obtained from this approach are substantially higher than rates as inferred from tide-gauge data. We therefore conclude that LECZs may be at higher risk of flooding, and within a shorter time horizon, than previously assumed.

scholarly journals Use of tide gauge data in operational oceanography and sea level hazard warning systems

2013 ◽  
Vol 6 (2) ◽  
pp. 1-18 ◽  
Author(s):  
B Pérez ◽  
E Álvarez Fanjul ◽  
S Pérez ◽  
M de Alfonso ◽  
J Vela
Keyword(s):  
Sea Level ◽  
Tide Gauge ◽  
Warning Systems ◽  
Tide Gauge Data ◽  
Operational Oceanography ◽  
Gauge Data ◽  
Hazard Warning ◽  
And Sea Level

scholarly journals Measuring rates of present-day relative sea-level rise in low-elevation coastal zones: a critical evaluation

Ocean Science ◽  
2019 ◽  
Vol 15 (1) ◽  
pp. 61-73 ◽  
Author(s):  
Molly E. Keogh ◽  
Torbjörn E. Törnqvist
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Land Surface ◽  
Tide Gauge ◽  
Tide Gauges ◽  
Coastal Zones ◽  
Tide Gauge Data ◽  
Relative Sea Level ◽  
Gauge Data ◽  
Coastal Louisiana

Abstract. Although tide gauges are the primary source of data used to calculate multi-decadal- to century-scale rates of relative sea-level change, we question the usefulness of tide-gauge data in rapidly subsiding low-elevation coastal zones (LECZs). Tide gauges measure relative sea-level rise (RSLR) with respect to the base of associated benchmarks. Focusing on coastal Louisiana, the largest LECZ in the United States, we find that these benchmarks (n=35) are anchored an average of 21.5 m below the land surface. Because at least 60 % of subsidence occurs in the top 5 m of the sediment column in this area, tide gauges in coastal Louisiana do not capture the primary contributor to RSLR. Similarly, global navigation satellite system (GNSS) stations (n=10) are anchored an average of > 14.3 m below the land surface and therefore also do not capture shallow subsidence. As a result, tide gauges and GNSS stations in coastal Louisiana, and likely in LECZs worldwide, systematically underestimate rates of RSLR as experienced at the land surface. We present an alternative approach that explicitly measures RSLR in LECZs with respect to the land surface and eliminates the need for tide-gauge data in this context. Shallow subsidence is measured by rod surface-elevation table–marker horizons (RSET-MHs) and added to measurements of deep subsidence from GNSS data, plus sea-level rise from satellite altimetry. We show that for an LECZ the size of coastal Louisiana (25 000–30 000 km2), about 40 RSET-MH instruments suffice to collect useful data. Rates of RSLR obtained from this approach are substantially higher than rates as inferred from tide-gauge data. We therefore conclude that LECZs may be at higher risk of flooding within a shorter time horizon than previously assumed.

Past, Present and Future Sea Levels in Singapore 

2021 ◽  
Author(s):  
Timothy Shaw ◽  
Stephen Chua ◽  
Jedrzej Majewski ◽  
Li Tanghua ◽  
Dhrubajyoti Samanta ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Land Surface ◽  
Tide Gauge ◽  
Ocean Dynamics ◽  
Tide Gauge Data ◽  
Sea Levels ◽  
Vertical Land Motion ◽  
Gauge Data ◽  
Probabilistic Projections

<p>Singapore is a small (728 km<sup>2</sup>) island nation that is vulnerable to rising sea levels with 30% of its land surface area less than 5 m above present sea level. Rising relative sea level (RSL), however, is not uniform with regional RSL changes differing from the global mean due to processes associated with vertical land motion (e.g., glacial-isostatic adjustment) and atmospheric and ocean dynamics. Understanding magnitudes, rates, and driving processes on past and present-day sea level are therefore important to provide greater confidence in accurately quantifying future sea-level rise projections and their uncertainty. Here, we present a synopsis of Singapore’s past and present RSL history using newly developed proxy RSL reconstructions from mangrove peats, coral microatolls and tide gauge data and conclude with probabilistic projections of future RSL change.</p><p>Past RSL is characterized by rapid rise during the early Holocene driven primarily by deglaciation of northern hemisphere ice sheets. Sea-level index points (SLIPs) from mangrove peats show sea levels rose rapidly from -20.7 m at 9.5 ka BP to -0.6 m at 7 ka BP at rates of 6-12 mm/yr. This is substantially greater than predicted magnitudes of RSL change from the ICE-6G_C GIA model which shows RSL increasing from -6.4 m at 9.5 ka BP to a ~2.8 m highstand at ~7 ka BP. SLIPs show the mid-Holocene highstand of ~4 ± 3.6 m at 5.2 ka BP before falling towards present at rates up to -2 mm/yr driven by hydro-isostatic processes. The nature of RSL changes during the mid- to late-Holocene transition remains poorly resolved with evidence of sea levels falling below present level to -2.2 ± 2.0 m at 1.2 ka BP. Present RSL reconstructions from coral microatolls coupled with tide-gauge data extend the limited instrumental period in this region beyond ~50 years. They show RSL rose ~0.03 m from 1915 to 1990 at 0.7 ± 1.4 mm/yr before increasing to 1.5 ± 2.1 mm/yr after 1990 to 2019. Future RSL change from probabilistic projections to 2100 under low (RCP 2.6) and high (RCP 8.5) emission scenarios show sea levels rising 0.43 m (50<sup>th</sup> percentile) (0.06 – 0.96 m; 95% credible interval) and 0.74 m (0.28 – 1.4 m), respectively. However, projected magnitudes of sea-level rise driven by rapid ice sheet dynamics and the unknown contribution of atmospheric and ocean dynamics in Southeast Asia have the potential to exacerbate projection magnitudes.</p>

scholarly journals Review article: Sea-level rise in Venice: historic and future trends

2020 ◽  
Author(s):  
Davide Zanchettin ◽  
Sara Bruni ◽  
Fabio Raicich ◽  
Piero Lionello ◽  
Fanny Adloff ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Tide Gauge ◽  
Tide Gauge Data ◽  
Relative Sea Level ◽  
Mean Sea Level ◽  
The Past ◽  
Gauge Data ◽  
Relative Sea Level Rise ◽  
Global Mean

Abstract. The City of Venice and the surrounding lagoonal ecosystem are highly vulnerable to variations in relative sea level. In the past ~150 years, this was characterized by a secular linear trend of about 2.5 mm/year resulting from the combined contributions of vertical land movement and sea-level rise. This literature review reassesses and synthesizes the progress achieved in understanding, estimating and predicting the individual contributions to local relative sea level, with focus on the most recent publications. The current best estimate of historical sea-level rise in Venice, based on tide-gauge data after removal of subsidence effects, is 1.23 ± 0.13 mm/year (period from 1872 to 2019). Subsidence thus contributed to about half of the observed relative sea-level rise over the same period. A higher – yet more uncertain – rate of sea-level rise is observed during recent decades, estimated from tide-gauge data to be about 2.76 ± 1.75 mm/year in the period 1993–2019 for the climatic component alone. An unresolved issue is the contrast between the observational capacity of tide gauges and satellite altimetry, with the latter tool not covering the Venice Lagoon. Water mass exchanges through the Gibraltar Strait currently constitute a source of substantial uncertainty for estimating future deviations of the Mediterranean mean sea-level trend from the global-mean value. Subsidence and regional atmospheric and oceanic circulation mechanisms can deviate Venetian relative sea-level trends from the global mean values for several decades. Regional processes will likely continue to determine significant interannual and interdecadal variability of Venetian sea level with magnitude comparable to that observed in the past, as well as non-negligible differential trends. Our estimate of the likely range of mean sea-level rise in Venice by 2100 due to climate change is presently estimated between 11 and 110 centimetres. An improbable yet possible high-end scenario linked to strong ice-sheet melting yields about 170 centimetres of mean sea-level rise in Venice by 2100. Projections of natural and human induced vertical land motions are currently not available, but historical evidence demonstrates that they can produce a significant contribution to the relative sea-level rise in Venice, further increasing the hazard posed by climatically-induced sea-level changes.

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