scholarly journals Ocean Bottom Deformation Due To Present‐Day Mass Redistribution and Its Impact on Sea Level Observations

2017 ◽  
Vol 44 (24) ◽  
Author(s):  
Thomas Frederikse ◽  
Riccardo E. M. Riva ◽  
Matt A. King
Keyword(s):  
Sea Level ◽  
Ocean Bottom ◽  
Bottom Deformation ◽  
Mass Redistribution

scholarly journals Sea Level Budgets Should Account for Ocean Bottom Deformation

2020 ◽  
Vol 47 (3) ◽  
Author(s):  
B. D. Vishwakarma ◽  
S. Royston ◽  
R. E. M. Riva ◽  
R. M. Westaway ◽  
J. L. Bamber
Keyword(s):  
Sea Level ◽  
Ocean Bottom ◽  
Bottom Deformation

Sea level response to Quartenary erosion and deposition in Scandinavia 

2021 ◽  
Author(s):  
Gustav Pallisgaard-Olesen ◽  
Vivi Kathrine Pedersen ◽  
Natalya Gomez
Keyword(s):  
Sea Level ◽  
Sea Level Changes ◽  
Glacial Cycles ◽  
Glacial Erosion ◽  
Erosion And Deposition ◽  
Late Pliocene ◽  
Glacial Origin ◽  
Sediment Deposits ◽  
Mass Redistribution ◽  
Global Sea Level

<div> <p>The landscape in western Scandinavia has undergone dramatic changes through numerous glaciations during the Quaternary. These changes in topography and in the volumes of offshore sediment deposits, have caused significant isostatic adjustments and local sea level changes, owing to erosional unloading and depositional loading of the lithosphere. Mass redistribution from erosion and deposition also has the potential to cause significant pertubations of the geoid, resulting in additional sea-level changes. The combined sea-level response from these processes, is yet to be investigated in detail for Scandinavia.</p> </div><div> <p>In this study we estimate the total sea level change from late-Pliocene- Quaternary glacial erosion and deposition in the Scandinavian region, using a gravitationally self-consistent global sea level model that includes the full viscoelastic response of the solid Earth to surface loading and unloading. In addition to the total late Pliocene-Quaternary mass redistribution, we <span>also </span>estimate transient sea level changes related specifically to the two latest glacial cycles.</p> </div><div> <p>We utilize existing observations of offshore sediment thicknesses of glacial origin, and combine these with estimates of onshore glacial erosion and estimates of erosion on the inner shelf. Based on these estimates, we can define mass redistribution and construct a preglacial landscape setting.</p> </div><div> <p>Our preliminary results show <span>perturbations of</span> the local sea level up to ∼ 200 m since<span> the</span> late-Pliocene in the Norwegian Sea, suggesting that erosion and deposition ha<span>ve</span> influenced the local paleo sea level history in Scandinavia significantly.</p> </div>

scholarly journals Seismic Characteristics of the Nootka Fault Zone: Results from the Seafloor Earthquake Array Japan–Canada Cascadia Experiment (SeaJade)

2019 ◽  
Vol 109 (6) ◽  
pp. 2252-2276 ◽  
Author(s):  
Jesse Hutchinson ◽  
Honn Kao ◽  
George Spence ◽  
Koichiro Obana ◽  
Kelin Wang ◽  
...  
Keyword(s):  
Sea Level ◽  
Fault Zone ◽  
Cascadia Subduction Zone ◽  
Ocean Bottom ◽  
Deformation Front ◽  
Thrust Faulting ◽  
Modes Of Failure ◽  
Ocean Bottom Seismometers ◽  
Thrust Zone ◽  
Depth Ranges

Abstract The Nootka fault zone (NFZ) divides the incoming Explorer and Juan de Fuca plates of the Cascadia subduction zone. Three months of seafloor monitoring using 33 ocean‐bottom seismometers off the west coast of Vancouver Island has allowed us to better understand the tectonic configuration and seismogenic characteristics of the NFZ. We have learned that the NFZ is comprised of northern and southern primary bounding faults, and several conjugate faults developed subperpendicular to the primary faults. Earthquakes typically occur over the depth ranges of 15–20 and 6–15 km along the primary bounding and conjugate faults, respectively. Focal mechanisms reveal that the most common modes of failure in this region are left‐lateral strike slip, with normal faulting occurring along the southwestern extent of the NFZ and thrust faulting to the northeast before the subduction front. Seismic tomography suggests that the oceanic Moho is at a depth of 12–14 km below sea level (10–12 km below seafloor) just seaward of the Cascadia deformation front, and that it deepens to 19 km (17 km below seafloor) approximately 20 km landward of the deformation front. Converted phase analysis illuminates four velocity‐contrasting interfaces with average depths below sea level deepening landward of the subduction front at ∼4–6, ∼6–9, ∼11–14, and ∼14–18  km. We interpret them as the sedimentary basement, upper–lower crust boundary, oceanic Moho, and the base of the highly fractured and seawater or mineral enriched veins within mantle. The precipitation of minerals such as quartz or the formation of talc, which is made possible by the intense degree of fracturing within the NFZ facilitating the infiltration of seawater, may reduce mantle velocities, as well as VP/VS ratios. The lack of seismicity observed along the interplate thrust zone in northern Cascadia may suggest that the megathrust fault is completely locked, consistent with prior studies.

scholarly journals The imprints of contemporary mass redistribution on regional sea level and vertical land motion observations

2019 ◽  
Author(s):  
Thomas Frederikse ◽  
Felix W. Landerer ◽  
Lambert Caron
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Tide Gauge ◽  
Large Fraction ◽  
Tide Gauge Records ◽  
Vertical Land Motion ◽  
Mass Redistribution ◽  
Uncertainty Estimates ◽  
Regional Sea Level ◽  
Sea Level Trend

Abstract. We derive trends and monthly anomalies in global and regional sea-level and solid-earth deformation that result from mass redistribution observed by GRACE and an ensemble of GIA models. With this ensemble, we do not only compute mean changes, but we also derive uncertainty estimates of all quantities. We find that over the GRACE era, the trend in land mass change has led to a sea-level trend of 1.28–1.82 mm/yr, which is driven by ice mass loss, while terrestrial water storage has increased over the GRACE period, causing a sea-level drop of 0.11–0.47 mm/yr. This redistribution of mass causes sea-level and deformation patterns that do not only vary in space, but also in time. The temporal variations affect GNSS-derived vertical land motion (VLM) observations, which are now commonly used to correct tide-gauge observations. We find that for many GNSS stations, including GNSS stations in coastal locations, solid-earth deformation resulting from present-day mass redistribution causes trends in the order of 1 mm/yr or higher. Since GNSS records often only span a few years, these trends are generally not representative for the tide-gauge records, which often span multiple decades, and extrapolating them backwards in time could cause substantial biases. To avoid this possible bias, we computed trends and associated uncertainties for 8228 GNSS stations after removing deformation due to GIA and present-day mass redistribution. With this separation, we are able to explain a large fraction of the discrepancy between observed sea-level trends at multiple long tide-gauge records and the reconstructed global-mean sea-level trend from recent reconstructions.

Impact of Low-Degree Stokes Coefficients and Spatial Leakage on Barystatic Sea-Level Rise from GRACE/GRACE-FO

2021 ◽  
Author(s):  
Maik Thomas ◽  
Henryk Dobslaw ◽  
Meike Bagge ◽  
Robert Dill ◽  
Volker Klemann ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Temporal Variations ◽  
Ocean Bottom ◽  
Spatial Integration ◽  
Buffer Zones ◽  
Ocean Mass ◽  
Low Degree ◽  
Gravity Fields ◽  
The Impact

<p>Temporal variations in the total ocean mass representing the barystatic part of present-day global-mean sea-level rise can be directly inferred from time-series of global gravity fields as provided by the GRACE and GRACE-FO missions. A spatial integration over all ocean regions, however, largely underestimates present-day rates as long as the effects of spatial leakage along the coasts of in particular Antarctica, Greenland, and the various islands of the Canadian Archipelago are not properly considered.</p><p>Based on the latest release 06 of monthly gravity fields processed at GFZ, we quantify (and subsequently correct) the contribution of spatial leakage to the post-processed mass anomalies of continental water storage and ocean bottom pressure. We find that by utilizing the sea level equation to predict spatially variable ocean mass trends out of the (leakage-corrected) terrrestial mass distributions from GRACE and GRACE-FO consistent results are obtained also from spatial integrations over ocean masks with different coastal buffer zones ranging from 400 to 1000 km. However, the results are critically dependent on coefficients of degree 1, 2 and 3, that are not precisely determined from GRACE data alone and need to be augemented by information from satellite laser ranging. We will particularly discuss the impact of those low-degree harmonics on the secular rates in global barystatic sea-level.</p>

scholarly journals Revisiting the contemporary sea-level budget on global and regional scales

2016 ◽  
Vol 113 (6) ◽  
pp. 1504-1509 ◽  
Author(s):  
Roelof Rietbroek ◽  
Sandra-Esther Brunnabend ◽  
Jürgen Kusche ◽  
Jens Schröter ◽  
Christoph Dahle
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Water Cycle ◽  
Joint Inversion ◽  
Ice Sheets ◽  
The Philippines ◽  
Ocean Bottom ◽  
Mass Rate ◽  
Sea Level Anomalies ◽  
The Pacific

Dividing the sea-level budget into contributions from ice sheets and glaciers, the water cycle, steric expansion, and crustal movement is challenging, especially on regional scales. Here, Gravity Recovery And Climate Experiment (GRACE) gravity observations and sea-level anomalies from altimetry are used in a joint inversion, ensuring a consistent decomposition of the global and regional sea-level rise budget. Over the years 2002–2014, we find a global mean steric trend of 1.38 ± 0.16 mm/y, compared with a total trend of 2.74 ± 0.58 mm/y. This is significantly larger than steric trends derived from in situ temperature/salinity profiles and models which range from 0.66 ± 0.2 to 0.94 ± 0.1 mm/y. Mass contributions from ice sheets and glaciers (1.37 ± 0.09 mm/y, accelerating with 0.03 ± 0.02 mm/y2) are offset by a negative hydrological component (−0.29 ± 0.26 mm/y). The combined mass rate (1.08 ± 0.3 mm/y) is smaller than previous GRACE estimates (up to 2 mm/y), but it is consistent with the sum of individual contributions (ice sheets, glaciers, and hydrology) found in literature. The altimetric sea-level budget is closed by coestimating a remaining component of 0.22 ± 0.26 mm/y. Well above average sea-level rise is found regionally near the Philippines (14.7 ± 4.39 mm/y) and Indonesia (8.3 ± 4.7 mm/y) which is dominated by steric components (11.2 ± 3.58 mm/y and 6.4 ± 3.18 mm/y, respectively). In contrast, in the central and Eastern part of the Pacific, negative steric trends (down to −2.8 ± 1.53 mm/y) are detected. Significant regional components are found, up to 5.3 ± 2.6 mm/y in the northwest Atlantic, which are likely due to ocean bottom pressure variations.

scholarly journals Icebergs Reveal Contours of the Ocean Bottom

Eos ◽  
2019 ◽  
Vol 100 ◽  
Author(s):  
Katherine Kornei
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Satellite Imagery ◽  
Water Depth ◽  
Ocean Bottom ◽  
Shed Light

Using satellite imagery of grounded icebergs near Greenland, researchers estimate the drafts of these ice masses and therefore water depth, measurements that shed light on future sea level rise.

scholarly journals RECESSION OF MARINE TERRACES - WITH SPECIAL REFERENCE TO THE COASTAL AREA NORTH OF SANTA CRUZ, CALIFORNIA

1968 ◽  
Vol 1 (11) ◽  
pp. 42
Author(s):  
Robert M. Sorenson
Keyword(s):  
Sea Level ◽  
Wave Climate ◽  
Army Corps ◽  
Ocean Bottom ◽  
Army Corps Of Engineers ◽  
Santa Cruz ◽  
Marine Terraces ◽  
History Of ◽  
Recession Rates ◽  
Area North

The concept "wave base" (or "surf base"), i.e. the maximum depth below mean sea level at which shoaling waves will effectively erode the ocean bottom leading to the recession of a shoreline, is discussed. Also, past and present opinions as to the magnitude of wave base in general and specifically in the area near Santa Cruz, California, and the variables controlling this phenomenon are presented. Then, an account of the author's successful and unsuccessful attempts to determine average rates of cliff retreat in the study area is presented along with the specific cliff recession rates obtained. These compare favorably with the recession rates measured by the U. S. Army Corps of Engineers for nearby areas of similar geology and topography and with rates determined for similar coastal areas in various parts of the world. A brief discussion of the spectrum of cliff recession rates found m areas of varying geology and wave climate is also presented. The accepted history of sea level since the last glacial maximum, particularly during the last 7,000 years, is reviewed as well as pertinent information on the geology, topography and wave climate of the study area. It is then shown that average recession rates estimated by relating extrapolated bedrock profiles of the lowest marine terraces with the accepted history of the latest sea level rise compare favorably with the recently measured recession rates. However, a conflict exists between the present wave-cut terrace profiles, the accepted history of sea level and the accepted value of wave base.

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