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Sea level: measuring the bounding surfaces of the ocean.

Tamisiea ME, Hughes CW, Williams SD, Bingley RM - Philos Trans A Math Phys Eng Sci (2014)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: National Oceanography Centre, Joseph Proudman Building, 6 Brownlow Street, Liverpool L3 5DA, UK mtam@noc.ac.uk.

No MeSH data available.


Related in: MedlinePlus

(a,b) Fingerprint of relative sea-level change caused by a mass loss scenario equivalent to 1 mm per year of globally averaged sea-level rise from (a) Greenland and (b) West Antarctica. The 1 mm per year contour is marked with a black line in these panels and in the colour bar. These results assume that mass loss occurs rapidly compared with the time over which the mantle would flow. Under this assumption, these maps can be scaled by the actual contributions from each region. (From fig. 4a,b in [33]. Copyright © 2011 The Oceanography Society, Inc.). (c–f) An example GIA model predication of change in (c) relative sea level (tide gauges), (d) geocentric sea level (altimetry), (e) geoid change (GRACE) and (f) crustal motion (GNSS) [34]. These results use a modified version [34] of the ICE-5G ice model and VM2 Earth model [35].
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RSTA20130336F3: (a,b) Fingerprint of relative sea-level change caused by a mass loss scenario equivalent to 1 mm per year of globally averaged sea-level rise from (a) Greenland and (b) West Antarctica. The 1 mm per year contour is marked with a black line in these panels and in the colour bar. These results assume that mass loss occurs rapidly compared with the time over which the mantle would flow. Under this assumption, these maps can be scaled by the actual contributions from each region. (From fig. 4a,b in [33]. Copyright © 2011 The Oceanography Society, Inc.). (c–f) An example GIA model predication of change in (c) relative sea level (tide gauges), (d) geocentric sea level (altimetry), (e) geoid change (GRACE) and (f) crustal motion (GNSS) [34]. These results use a modified version [34] of the ICE-5G ice model and VM2 Earth model [35].

Mentions: Many processes can drive the change to the geoid and crust, on a wide range of time scales. One of the most-modelled examples is the effect of mass loss from ice sheets and glaciers on sea-level change. (Other processes, such as earthquakes, can have large regional effects, but the global impact on sea-level estimates is not as extensively modelled [20,21].) The mass component of the associated freshwater flux into the oceans would be redistributed globally on a subweekly time scale by barotropic waves [22–24]. (Sea-level variations are also driven by the resulting temperature and salinity perturbations, but these take much longer to redistribute [25].) However, this does not imply that the rapid mass redistribution would be uniform [26–30]. The redistribution of mass drives crustal motion and gravity changes, which introduce long length-scale variations into the sea-level change. Initially, the response of the Earth is nearly elastic, i.e. deformation occurs as soon as the surface or potential load changes and recovers as soon as the load returns to its initial state. A demonstration that the Earth does respond on very short time scales to changing applied forces is the solid Earth's centimetre-level tidal response [31,32]. Figure 3a,b shows model predictions for tide gauge measurements of sea level measured relative to the crust as a result of mass loss from Greenland and West Antarctica [33]. In regions where the mass loss occurs, whether owing to sublimation, melting or discharge, the gravitational attraction is reduced, causing the geoid to lower near the ice sheet. Thus, an altimeter would observe a sea-level fall. However, this fall is even larger for a tide gauge measurement in the region owing to the resulting crustal uplift. Owing to this near-field relative sea-level fall and a need for this to be balanced in the global average, far-field sea level in some regions must rise by more than average.Figure 3.


Sea level: measuring the bounding surfaces of the ocean.

Tamisiea ME, Hughes CW, Williams SD, Bingley RM - Philos Trans A Math Phys Eng Sci (2014)

(a,b) Fingerprint of relative sea-level change caused by a mass loss scenario equivalent to 1 mm per year of globally averaged sea-level rise from (a) Greenland and (b) West Antarctica. The 1 mm per year contour is marked with a black line in these panels and in the colour bar. These results assume that mass loss occurs rapidly compared with the time over which the mantle would flow. Under this assumption, these maps can be scaled by the actual contributions from each region. (From fig. 4a,b in [33]. Copyright © 2011 The Oceanography Society, Inc.). (c–f) An example GIA model predication of change in (c) relative sea level (tide gauges), (d) geocentric sea level (altimetry), (e) geoid change (GRACE) and (f) crustal motion (GNSS) [34]. These results use a modified version [34] of the ICE-5G ice model and VM2 Earth model [35].
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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RSTA20130336F3: (a,b) Fingerprint of relative sea-level change caused by a mass loss scenario equivalent to 1 mm per year of globally averaged sea-level rise from (a) Greenland and (b) West Antarctica. The 1 mm per year contour is marked with a black line in these panels and in the colour bar. These results assume that mass loss occurs rapidly compared with the time over which the mantle would flow. Under this assumption, these maps can be scaled by the actual contributions from each region. (From fig. 4a,b in [33]. Copyright © 2011 The Oceanography Society, Inc.). (c–f) An example GIA model predication of change in (c) relative sea level (tide gauges), (d) geocentric sea level (altimetry), (e) geoid change (GRACE) and (f) crustal motion (GNSS) [34]. These results use a modified version [34] of the ICE-5G ice model and VM2 Earth model [35].
Mentions: Many processes can drive the change to the geoid and crust, on a wide range of time scales. One of the most-modelled examples is the effect of mass loss from ice sheets and glaciers on sea-level change. (Other processes, such as earthquakes, can have large regional effects, but the global impact on sea-level estimates is not as extensively modelled [20,21].) The mass component of the associated freshwater flux into the oceans would be redistributed globally on a subweekly time scale by barotropic waves [22–24]. (Sea-level variations are also driven by the resulting temperature and salinity perturbations, but these take much longer to redistribute [25].) However, this does not imply that the rapid mass redistribution would be uniform [26–30]. The redistribution of mass drives crustal motion and gravity changes, which introduce long length-scale variations into the sea-level change. Initially, the response of the Earth is nearly elastic, i.e. deformation occurs as soon as the surface or potential load changes and recovers as soon as the load returns to its initial state. A demonstration that the Earth does respond on very short time scales to changing applied forces is the solid Earth's centimetre-level tidal response [31,32]. Figure 3a,b shows model predictions for tide gauge measurements of sea level measured relative to the crust as a result of mass loss from Greenland and West Antarctica [33]. In regions where the mass loss occurs, whether owing to sublimation, melting or discharge, the gravitational attraction is reduced, causing the geoid to lower near the ice sheet. Thus, an altimeter would observe a sea-level fall. However, this fall is even larger for a tide gauge measurement in the region owing to the resulting crustal uplift. Owing to this near-field relative sea-level fall and a need for this to be balanced in the global average, far-field sea level in some regions must rise by more than average.Figure 3.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: National Oceanography Centre, Joseph Proudman Building, 6 Brownlow Street, Liverpool L3 5DA, UK mtam@noc.ac.uk.

No MeSH data available.


Related in: MedlinePlus