scholarly journals A 180-Million-Year Record of Sea Level and Ice Volume Variations from Continental Margin and Deep-Sea Isotopic Records

Oceanography ◽  
2011 ◽  
Vol 24 (2) ◽  
pp. 40-53 ◽  
Author(s):  
Kenneth Miller ◽  
Gregory Mountain ◽  
James Wright ◽  
James Browning
Keyword(s):  
Sea Level ◽  
Continental Margin ◽  
Deep Sea ◽  
Ice Volume ◽  
Isotopic Records

Antarctic ice volume for the last 740 ka calculated with a simple ice sheet model

2005 ◽  
Vol 17 (2) ◽  
pp. 281-287 ◽  
Author(s):  
J. OERLEMANS
Keyword(s):  
Sea Level ◽  
Deep Sea ◽  
Relative Phase ◽  
Ice Sheet ◽  
Ice Cores ◽  
Temperature History ◽  
Glacial Cycle ◽  
Ice Volume ◽  
The Antarctic ◽  
And Sea Level

Fluctuations in the volume of the Antarctic ice sheet for the last 740 ka are calculated by forcing a simple ice sheet model with a sea-level history (from a composite deep sea δ18O record) and a temperature history (from the Dome C deuterium record). Antarctic ice volume reaches maximum values of about 30 × 1015 m3, 3 to 8 ka after glacial maxima [defined as maximum values of the deep sea δ18O record]. Minimum values of ice volume reached in the course of interglacial periods are about 26 × 1015 m3. Most of the time the temperature forcing (larger accumulation) and sea-level forcing (grounding-line retreat) tend to have competing effects. However, towards the end of a glacial cycle, when temperature rises and sea-level is still relatively low, the ice volume reaches a peak. The peak value is very sensitive to the relative phase of the sea-level forcing with respect to the temperature forcing. This is further studied by looking at the response of the model to purely periodic forcings with different relative phase. The large sensitivity of ice sheet size to the phase of the forcings may have some implications for dating of deep ice cores. Care has to be taken by using anchor points from the deep sea record.

scholarly journals Sea level and deep-sea temperature reconstructions suggest quasi-stable states and critical transitions over the past 40 million years

2021 ◽  
Vol 7 (26) ◽  
pp. eabf5326
Author(s):  
Eelco J. Rohling ◽  
Jimin Yu ◽  
David Heslop ◽  
Gavin L. Foster ◽  
Bradley Opdyke ◽  
...  
Keyword(s):  
Sea Level ◽  
Deep Sea ◽  
Dynamical Behavior ◽  
Linear Scaling ◽  
Sea Level Changes ◽  
Stable States ◽  
Sea Temperature ◽  
Ice Volume ◽  
The Past ◽  
Critical Transitions

Sea level and deep-sea temperature variations are key indicators of global climate changes. For continuous records over millions of years, deep-sea carbonate microfossil–based δ18O (δc) records are indispensable because they reflect changes in both deep-sea temperature and seawater δ18O (δw); the latter are related to ice volume and, thus, to sea level changes. Deep-sea temperature is usually resolved using elemental ratios in the same benthic microfossil shells used for δc, with linear scaling of residual δw to sea level changes. Uncertainties are large and the linear-scaling assumption remains untested. Here, we present a new process-based approach to assess relationships between changes in sea level, mean ice sheet δ18O, and both deep-sea δw and temperature and find distinct nonlinearity between sea level and δw changes. Application to δc records over the past 40 million years suggests that Earth’s climate system has complex dynamical behavior, with threshold-like adjustments (critical transitions) that separate quasi-stable deep-sea temperature and ice-volume states.

scholarly journals The response of a simple Antarctic ice-flow model to temperature and sea-level fluctuations over the Cenozoic era

2007 ◽  
Vol 46 ◽  
pp. 69-77 ◽  
Author(s):  
C.I. Van Tuyll ◽  
R.S.W. Van De Wal ◽  
J. Oerlemans
Keyword(s):  
Sea Level ◽  
Deep Sea ◽  
Flow Model ◽  
Ice Sheet ◽  
Temperature Record ◽  
Ice Flow ◽  
Antarctic Ice Sheet ◽  
Sea Temperature ◽  
Ice Volume ◽  
The Antarctic

AbstractAn ice-flow model is used to simulate the Antarctic ice-sheet volume and deep-sea temperature record during Cenozoic times. We used a vertically integrated axisymmetric ice-sheet model, including bedrock adjustment. In order to overcome strong numerical hysteresis effects during climate change, the model is solved on a stretching grid. The Cenozoic reconstruction of the Antarctic ice sheet is accomplished by splitting the global oxygen isotope record derived from benthic foraminifera into an ice-volume and a deep-sea temperature component. The model is tuned to reconstruct the initiation of a large ice sheet of continental size at 34 Ma. The resulting ice volume curve shows that small ice caps (<107 km3) could have existed during Paleocene and Eocene times. Fluctuations during the Miocene are large, indicating a retreat back from the coast and a vanishing ice flux across the grounding line, but with ice volumes still up to 60% of the present-day volume. The resulting deep-sea temperature curve shows similarities with the paleotemperature curve derived from Mg/Ca in benthic calcite from 25 Ma till the present, which supports the idea that the ice volume is well reproduced for this period. Before 34 Ma, the reproduced deep-sea temperature is slightly higher than is generally assumed. Global sea-level change turns out to be of minor importance when considering the Cenozoic evolution of the ice sheet until 5 Ma.

THE STRUCTURE OF THE NATURALISTE PLATEAU AND TROUGH

1977 ◽  
Vol 17 (1) ◽  
pp. 3 ◽  
Author(s):  
Derk Jongsma ◽  
Peter Petkovic
Keyword(s):  
Sea Level ◽  
Early Cretaceous ◽  
Continental Margin ◽  
Deep Sea ◽  
Magnetic Anomalies ◽  
Seismic Profiles ◽  
Northern Margin ◽  
Reflection Seismic ◽  
Southwest Australia ◽  
Water Depths

The Naturaliste Plateau is a broad, relatively flat feature lying at a depth below sea level of around 2500 m off the continental margin of southwest Australia. A northerly trending trough with water depths of 3000 to 4000 m separates the Plateau from the continental shelf. Reflection seismic profiles over the Plateau reveal 500 to 1000 m thicknesses of post-Neocomian sediments on the Plateau and up to 2000 m thicknesses in the Trough. An erosional unconformity which is thought to be of Neocomian age separates folded, faulted sediments and intruded metamorphic and igneous basement from the overlying sediments. Deep sea drilling has shown the upper section as being composed of deep-sea clays and oozes. Several hiatuses occur in this upper section.Magnetic anomalies over the Plateau are intense and have magnitudes of up to 850 nT. The anomalies are much more subdued over the Trough. Depths to the bodies causing the magnetic anomalies are estimated to be between zero and three km below the Neocomian unconformity. The gravity field over the Plateau indicates that the crust is of intermediate thickness. A phase of rifting in the Early Cretaceous gave rise to a gently sloping northern margin, whereas rifting in the Eocene produced a steep, faulted, southern margin. The Plateau appears to have been at its present depths since the Early Cretaceous. Prospectivity for petroleum over the Plateau and Trough is poor.

scholarly journals On the geophysical processes impacting palaeo-sea-level observations

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Yusuke Yokoyama ◽  
Anthony Purcell
Keyword(s):  
Sea Level ◽  
Large Scale ◽  
Global Climate ◽  
Sea Level Change ◽  
Sea Level Changes ◽  
Factors Affecting ◽  
Ice Volume ◽  
Level Change ◽  
Recent Developments ◽  
Geophysical Processes

AbstractPast sea-level change represents the large-scale state of global climate, reflecting the waxing and waning of global ice sheets and the corresponding effect on ocean volume. Recent developments in sampling and analytical methods enable us to more precisely reconstruct past sea-level changes using geological indicators dated by radiometric methods. However, ice-volume changes alone cannot wholly account for these observations of local, relative sea-level change because of various geophysical factors including glacio-hydro-isostatic adjustments (GIA). The mechanisms behind GIA cannot be ignored when reconstructing global ice volume, yet they remain poorly understood within the general sea-level community. In this paper, various geophysical factors affecting sea-level observations are discussed and the details and impacts of these processes on estimates of past ice volumes are introduced.

Assessing the Global Meltwater Spike

1982 ◽  
Vol 17 (2) ◽  
pp. 148-172 ◽  
Author(s):  
Glenn A. Jones ◽  
William F. Ruddiman
Keyword(s):  
Deep Sea ◽  
Planktonic Foraminifera ◽  
World Ocean ◽  
Equatorial Atlantic ◽  
Low Salinity ◽  
Ice Volume ◽  
Middle Latitudes ◽  
Mixing Intensity ◽  
Entire World ◽  
Isotopic Signal

AbstractL. V. Worthington (1968, Meteorological Monographs 8, 63–67) hypothesized that a low-salinity lid covered the entire world ocean. By deconvolving isotopic curves from the western equatorial Pacific and equatorial Atlantic, W. H. Berger, R. F. Johnson, and J. S. Killingley (1977), Nature (London) 269, 661–663) and W. H. Berger (1978, Deep-Sea Research 25, 473–480) reconstructed “meltwater spikes” similar to those actually observed in the Gulf of Mexico and thus apparently confirmed the Worthington hypothesis. It is shown that this conclusion is unwarranted. The primary flaw in the reconstructed meltwater spikes is that the mixing intensity used in the deconvolution operation is overestimated. As a result, structure recorded in the mixed isotopic record becomes exaggerated in the attempt to restore the original unmixed record. This structure can be attributed to variable ice-volume decay during deglaciation, effects of differential solution on planktonic foraminifera, temporal changes in abundance of the foraminifera carrying the isotopic signal, and analytical error. An alternative geographic view to the global low-salinity lid is offered: a map showing portions of the ocean potentially affected by increased deglacial meltwater at middle and high latitudes and by increased precipitation-induced runoff at low and middle latitudes.

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