scholarly journals Sea level, paleogeography, and archeology on California's Northern Channel islands

2015 ◽  
Vol 83 (2) ◽  
pp. 263-272 ◽  
Author(s):  
Leslie Reeder-Myers ◽  
Jon M. Erlandson ◽  
Daniel R. Muhs ◽  
Torben C. Rick
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Late Pleistocene ◽  
New World ◽  
Channel Islands ◽  
Glacial Isostatic Adjustment ◽  
Human Occupation ◽  
Isostatic Adjustment ◽  
The World ◽  
Northern Channel Islands

Sea-level rise during the late Pleistocene and early Holocene inundated nearshore areas in many parts of the world, producing drastic changes in local ecosystems and obscuring significant portions of the archeological record. Although global forces are at play, the effects of sea-level rise are highly localized due to variability in glacial isostatic adjustment (GIA) effects. Interpretations of coastal paleoecology and archeology require reliable estimates of ancient shorelines that account for GIA effects. Here we build on previous models for California's Northern Channel Islands, producing more accurate late Pleistocene and Holocene paleogeographic reconstructions adjusted for regional GIA variability. This region has contributed significantly to our understanding of early New World coastal foragers. Sea level that was about 80-85 m lower than present at the time of the first known human occupation brought about a landscape and ecology substantially different than today. During the late Pleistocene, large tracts of coastal lowlands were exposed, while a colder, wetter climate and fluctuating marine conditions interacted with rapidly evolving littoral environments. At the close of the Pleistocene and start of the Holocene, people in coastal California faced shrinking land, intertidal, and subtidal zones, with important implications for resource availability and distribution.

Glacial isostatic adjustment near the center of the former Patagonian Ice Sheet (48°S) during the last 16.5 kyr

2021 ◽  
Author(s):  
Matthias Troch ◽  
Sebastien Bertrand ◽  
Carina B. Lange ◽  
Paola Cardenas ◽  
Helge Arz ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Average Rate ◽  
Ice Sheet ◽  
Late Glacial ◽  
Glacial Isostatic Adjustment ◽  
Isostatic Rebound ◽  
Isostatic Adjustment ◽  
Modelling Studies ◽  
Global Sea Level

<p>Our understanding of glacial isostatic rebound across Patagonia is highly limited, despite its importance to constrain past ice volume estimates and better comprehend relative sea-level variations. With this in mind, our research objective is to reconstruct the magnitude and rate of Late Glacial to Holocene glacial isostatic adjustment near the center of the former Patagonian Ice Sheet. We focus on Larenas Bay (48°S; 1.26 km<sup>2</sup>), which is connected to Baker Channel through a shallow (<em>ca.</em> 7.4 m) and narrow (<em>ca.</em> 150 m across) inlet, and hence has the potential to record periods of basin isolation and marine ingression. The paleoenvironmental evolution of the bay was investigated through a sedimentological analysis of a 9.2 m long, radiocarbon-dated, sediment core covering the last 16.8 cal. kyr BP. Salinity indicators, including diatom paleoecology, alkenone concentrations and CaCO<sub>3</sub> content, were used to reconstruct the bay’s connectivity to the fjord. Results indicate that Larenas Bay was a marine environment before 16.5 cal. kyr BP and after 9.1 cal. kyr BP, but that it was disconnected from Baker Channel in-between. We infer that glacial isostatic adjustment outpaced global sea-level rise between 16.5 – 9.1 cal. kyr BP. During the Late Glacial - Holocene transition, the center of the former Patagonian Ice Sheet rose <em>ca.</em> 96 m, at an average rate of 1.30 cm/year. During the remainder of the Holocene, glacial isostatic adjustment continued (<em>ca.</em> 19.5 m), but at a slower average pace of 0.21 cm/year. Comparisons between multi-centennial variations in the salinity indicators and existing records of global sea-level rise suggest that the glacial isostatic adjustment rate fluctuated during these time intervals, in agreement with local glacier dynamics. More specifically, most of the glacial isostatic adjustment registered between 16.5 – 9.1 cal. kyr BP seems to have occurred before meltwater pulse 1A (14.5 – 14.0 kyr BP). Likewise, it appears that the highest Holocene glacial isostatic rebound rates occurred during the last 1.4 kyr, most likely in response to glacier recession from Neoglacial maxima. This implies a relatively rapid response of the local solid earth to ice unloading, which agrees with independent modelling studies investigating contemporary uplift. We conclude that the center of the former Patagonian Ice Sheet experienced a glacial isostatic adjustment of <em>ca.</em> 115 m over the last 16.5 kyr, and that >80% occurred during the Late Glacial and early Holocene.</p>

scholarly journals SELEN<sup>4</sup> (SELEN version 4.0): a Fortran program for solving the gravitationally and topographically self-consistent Sea Level Equation in Glacial Isostatic Adjustment modeling

2019 ◽  
Author(s):  
Giorgio Spada ◽  
Daniele Melini
Keyword(s):  
Open Source ◽  
Sea Level ◽  
Late Pleistocene ◽  
Ice Sheets ◽  
Glacial Isostatic Adjustment ◽  
Open Source Program ◽  
Isostatic Adjustment ◽  
Source Program ◽  
Supplementary Document ◽  
Self Consistent

Abstract. We present SELEN4 (a SealEveL EquatioN solver), an open-source program written in Fortran 90 that simulates the Glacial Isostatic Adjustment (GIA) process in response to the melting of the late-Pleistocene ice sheets. Using a pseudo-spectral approach complemented by a spatial discretization on an icosahedron-based spherical geodesic grid, SELEN4 solves a generalised Sea Level Equation (SLE) for a spherically symmetric Earth with linear viscoelastic rheology, taking the migration of the shorelines and the rotational feedback on sea level into account. The approach is gravitationally and topographically self-consistent, since it considers the gravitational interactions between the solid Earth, the cryosphere and the oceans, and it accounts for the evolution of the Earth's topography in response to changes in sea level. Program SELEN4 can be employed to study a broad range of geophysical effects of GIA, including past relative sea-level variations induced by the melting of the late-Pleistocene ice sheets, the time-evolution of paleogeography and of the ocean function since the Last Glacial Maximum, the history of the Earth's rotational variations, present-day geodetic signals observed by Global Navigation Satellite Systems and geopotential field variations detected by satellite gravity missions like GRACE (the Gravity Recovery and Climate Experiment). The GIA fingerprints constitute a standard output of SELEN4. Along with the source code, we provide a supplementary document with a full account of the theory, some numerical results obtained from a standard run, and a User guide. Program SELEN was conceived by GS in 2005 as a tool for students eager to learn about GIA. Still, it is the only open-source program for the solution of the SLE available to the community.

scholarly journals Optimal locations of sea-level indicators in glacial isostatic adjustment investigations

2013 ◽  
Vol 5 (2) ◽  
pp. 2419-2448 ◽  
Author(s):  
H. Steffen ◽  
P. Wu ◽  
H. Wang
Keyword(s):  
Sea Level ◽  
Element Formulation ◽  
Glacial Isostatic Adjustment ◽  
Load History ◽  
Lithospheric Thickness ◽  
Ice Load ◽  
Isostatic Adjustment ◽  
Almost Everywhere ◽  
The World ◽  
Thickness Variations

Abstract. Fréchet (sensitivity) kernels are an important tool in glacial isostatic adjustment (GIA) investigations to understand lithospheric thickness, mantle viscosity and ice-load model variations. These parameters influence the interpretation of geologic, geophysical and geodetic data, which contribute to our understanding of global change. Recently, sensitivity kernels have been extended to laterally heterogeneous Earth models using the finite-element formulation, which enabled detailed studies on the sensitivity of the different geodetic observations of GIA such as GPS and terrestrial and space gravimetry. In this study, we discuss global sensitivities of relative sea-level (RSL) data of the last 18 000 yr. This also includes indicative RSL-like data (e.g. lake levels) on the continents far off the coasts. We present detailed sensitivity maps for four parameters important in GIA investigations (ice-load history, lithospheric thickness, background viscosity, lateral viscosity variations) for up to 9 dedicated times. Assuming an accuracy of 2 m of RSL data of all ages, we highlight areas around the world where, if the environmental conditions allowed its deposition and survival until today, RSL data of at least this accuracy may help to quantify the GIA modelling parameters above. The sensitivity to ice-load history variations is the dominating pattern covering in times of 14 ka BP and older almost the whole world. Lithospheric thickness variations are mainly only possible to be determined in certain high-latitude areas around the large former and current ice sheets. Background viscosity as well as lateral viscosity variations can be traced at most coast and shelf areas around the world, especially when dated to be older than 10 ka BP. The latter three are almost everywhere overlapped by the ice-load history pattern. In general we find that the more recent the data are, the smaller is the area of possible RSL locations which could provide enough information on the four GIA modelling parameters. But, we also note that when the accuracy of RSL data can be improved, e.g. from 2 m to 1 m, these areas become larger allowing better inference of background viscosity and lateral heterogeneity. Although the patterns depend on the chosen models and error limit, our results are indicative enough to outline areas where one should look for helpful RSL data of a certain time period.

scholarly journals SELEN<sup>4</sup> (SELEN version 4.0): a Fortran program for solving the gravitationally and topographically self-consistent sea-level equation in glacial isostatic adjustment modeling

2019 ◽  
Vol 12 (12) ◽  
pp. 5055-5075 ◽  
Author(s):  
Giorgio Spada ◽  
Daniele Melini
Keyword(s):  
Sea Level ◽  
Late Pleistocene ◽  
Ice Sheets ◽  
Global Navigation Satellite Systems ◽  
Glacial Isostatic Adjustment ◽  
Satellite Gravity ◽  
Full Account ◽  
Isostatic Adjustment ◽  
Supplementary Document ◽  
Self Consistent

Abstract. We present SELEN4 (SealEveL EquatioN solver), an open-source program written in Fortran 90 that simulates the glacial isostatic adjustment (GIA) process in response to the melting of the Late Pleistocene ice sheets. Using a pseudo-spectral approach complemented by a spatial discretization on an icosahedron-based spherical geodesic grid, SELEN4 solves a generalized sea-level equation (SLE) for a spherically symmetric Earth with linear viscoelastic rheology, taking the migration of the shorelines and the rotational feedback on sea level into account. The approach is gravitationally and topographically self-consistent, since it considers the gravitational interactions between the solid Earth, the cryosphere, and the oceans, and it accounts for the evolution of the Earth's topography in response to changes in sea level. The SELEN4 program can be employed to study a broad range of geophysical effects of GIA, including past relative sea-level variations induced by the melting of the Late Pleistocene ice sheets, the time evolution of paleogeography and of the ocean function since the Last Glacial Maximum, the history of the Earth's rotational variations, present-day geodetic signals observed by Global Navigation Satellite Systems, and gravity field variations detected by satellite gravity missions like GRACE (the Gravity Recovery and Climate Experiment). The “GIA fingerprints” constitute a standard output of SELEN4. Along with the source code, we provide a supplementary document with a full account of the theory, some numerical results obtained from a standard run, and a user guide. Originally, the SELEN program was conceived by Giorgio Spada (GS) in 2005 as a tool for students eager to learn about GIA, and it has been the first SLE solver made available to the community.

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