The last deglaciation of Cape Adare, northern Victoria Land, Antarctica

2008 ◽  
Vol 20 (6) ◽  
pp. 581-587 ◽  
Author(s):  
Joanne S. Johnson ◽  
Claus-Dieter Hillenbrand ◽  
John L. Smellie ◽  
Sergio Rocchi
Keyword(s):  
Before Present ◽  
Last Deglaciation ◽  
Last Glacial Period ◽  
Radiocarbon Dates ◽  
Exposure Age ◽  
Victoria Land ◽  
Younger Age ◽  
The Last Deglaciation ◽  
Exposure Ages ◽  
The Last Glacial

AbstractWe present two 10Be exposure ages from erratic boulders at Cape Adare, northern Victoria Land. The exposure ages obtained suggest that Cape Adare was covered by ice during the last glacial period, and the younger age points to deglaciation around 16.2 ka. Comparison of our younger 10Be exposure age with published radiocarbon dates for Adélie penguin occupation at Cape Adare suggests that the onset of penguin colonization (at 2–3 kyr before present) lagged behind the deglaciation by at least 11.5 kyr. These observations indicate that penguin colonization did not occur until several thousand years after ice free ground became available.

scholarly journals CH<sub>4</sub> and N<sub>2</sub>O fluctuations during the penultimate deglaciation

2021 ◽  
Vol 17 (4) ◽  
pp. 1627-1643
Author(s):  
Loïc Schmidely ◽  
Christoph Nehrbass-Ahles ◽  
Jochen Schmitt ◽  
Juhyeong Han ◽  
Lucas Silva ◽  
...  
Keyword(s):  
Ice Core ◽  
Last Deglaciation ◽  
Glacial Cycle ◽  
Last Glacial Period ◽  
Modes Of Variability ◽  
The Past ◽  
Present Composite ◽  
The Last Deglaciation ◽  
Ch4 And N2o ◽  
The Last Glacial

Abstract. Deglaciations are characterized by the largest natural changes in methane (CH4) and nitrous oxide (N2O) concentrations of the past 800 000 years. Reconstructions of millennial- to centennial-scale variability within these periods are mostly restricted to the last deglaciation. In this study, we present composite records of CH4 and N2O concentrations from the EPICA Dome C ice core covering the penultimate deglaciation at temporal resolutions of ∼100 years. Our data permit the identification of centennial-scale fluctuations during the transition from glacial to interglacial levels. At ∼134 000 and ∼129 000 years before present (hereafter ka), both CH4 and N2O increased on centennial timescales. These abrupt rises are similar to the fluctuations associated with the Dansgaard–Oeschger events identified in the last glacial period. In addition, gradually rising N2O levels at ∼130 ka resemble a pattern of increasing N2O concentrations on millennial timescales characterizing the later part of Heinrich stadials. Overall, the events in CH4 and N2O during the penultimate deglaciation exhibit modes of variability that are also found during the last deglaciation and glacial cycle, suggesting that the processes leading to changes in emission during the transitions were similar but their timing differed.

scholarly journals Near-constant retreat rate of a terrestrial margin of the Laurentide Ice Sheet during the last deglaciation

Geology ◽  
2021 ◽  
Author(s):  
Thomas V. Lowell ◽  
Meredith A. Kelly ◽  
Jennifer A. Howley ◽  
Timothy G. Fisher ◽  
Peter J. Barnett ◽  
...  
Keyword(s):  
Bayesian Modeling ◽  
Gradual Increase ◽  
Ice Core ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Last Deglaciation ◽  
Last Glacial Period ◽  
The Last Deglaciation ◽  
Temperature Records ◽  
The Last Glacial

The Laurentide Ice Sheet (LIS) was the largest ice sheet during the last glacial period. An accurate representation of its behavior during the last deglaciation is critical to understanding its influence on and response to a changing climate. We use 10Be dating and Bayesian modeling to track the recession of the southwest sector of the Labrador Dome of the LIS along an ~500-km-long transect west of Lake Superior during the last deglaciation. This transect reflects terrestrial ice-margin retreat and crosses multiple moraine sets, with the southwestern part of the transect deglaciated by ca. 19 ka and the northeastern part deglaciated by ca. 10 ka. The predominant behavior of the ice margin during this interval is near-constant retreat with retreat rates varying between ~59 m/a and 38 m/a. The moraine sets mark standstills and/or readvances that in total constitute only ~17% of the retreat interval. The spatial and temporal pattern of ice-margin retreat tracked here differs from existing reconstructions that are based on using isochrons to define ice-margin positions. Acknowledging the uncertainties associated with the modeled ages of ice-margin retreat, we suggest that the overall retreat pattern is consistent with forcing by a gradual increase in Northern Hemisphere, high-latitude summer insolation. The pattern of ice-margin retreat is inconsistent with Greenland ice-core temperature records, and thus these records may not be suitable to drive models of the LIS.

scholarly journals Equatorial Pacific seawater pCO2 variability since the last glacial period

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Kaoru Kubota ◽  
Yusuke Yokoyama ◽  
Tsuyoshi Ishikawa ◽  
Takuya Sagawa ◽  
Minoru Ikehara ◽  
...  
Keyword(s):  
Isotope Analysis ◽  
Equatorial Pacific ◽  
Equatorial Pacific Ocean ◽  
Last Deglaciation ◽  
Last Glacial Period ◽  
Near Surface ◽  
Surface Dwelling ◽  
The Last Deglaciation ◽  
Global Carbon ◽  
The Last Glacial

Abstract The ocean may have played a central role in the atmospheric pCO2 rise during the last deglaciation. However, evidence on where carbon was exchanged between the ocean and the atmosphere in this period is still lacking, hampering our understanding of global carbon cycle on glacial–interglacial timescales. Here we report a new surface seawater pCO2 reconstruction for the western equatorial Pacific Ocean based on boron isotope analysis—a seawater pCO2 proxy—using two species of near-surface dwelling foraminifera from the same marine sediment core. The results indicate that the region remained a modest CO2 sink throughout the last deglaciation.

scholarly journals <i>δ</i><sup>13</sup>C decreases in the upper western South Atlantic during Heinrich Stadials 3 and 2

2017 ◽  
Vol 13 (4) ◽  
pp. 345-358 ◽  
Author(s):  
Marília C. Campos ◽  
Cristiano M. Chiessi ◽  
Ines Voigt ◽  
Alberto R. Piola ◽  
Henning Kuhnert ◽  
...  
Keyword(s):  
Climate Change ◽  
South Atlantic ◽  
Meridional Overturning Circulation ◽  
Glacial Period ◽  
Last Deglaciation ◽  
Last Glacial Period ◽  
Last Glacial ◽  
Change Events ◽  
The Last Glacial ◽  
Millennial Scale

Abstract. Abrupt millennial-scale climate change events of the last deglaciation (i.e. Heinrich Stadial 1 and the Younger Dryas) were accompanied by marked increases in atmospheric CO2 (CO2atm) and decreases in its stable carbon isotopic ratios (δ13C), i.e. δ13CO2atm, presumably due to outgassing from the ocean. However, information on the preceding Heinrich Stadials during the last glacial period is scarce. Here we present δ13C records from two species of planktonic foraminifera from the western South Atlantic that reveal major decreases (up to 1 ‰) during Heinrich Stadials 3 and 2. These δ13C decreases are most likely related to millennial-scale periods of weakening of the Atlantic meridional overturning circulation and the consequent increase (decrease) in CO2atm (δ13CO2atm). We hypothesise two mechanisms that could account for the decreases observed in our records, namely strengthening of Southern Ocean deep-water ventilation and weakening of the biological pump. Additionally, we suggest that air–sea gas exchange could have contributed to the observed δ13C decreases. Together with other lines of evidence, our data are consistent with the hypothesis that the CO2 added to the atmosphere during abrupt millennial-scale climate change events of the last glacial period also originated in the ocean and reached the atmosphere by outgassing. The temporal evolution of δ13C during Heinrich Stadials 3 and 2 in our records is characterized by two relative minima separated by a relative maximum. This w structure is also found in North Atlantic and South American records, further suggesting that such a structure is a pervasive feature of Heinrich Stadial 2 and, possibly, also Heinrich Stadial 3.

Postglacial dispersal of freshwater fishes into Ontario

1992 ◽  
Vol 70 (11) ◽  
pp. 2247-2259 ◽  
Author(s):  
Nicholas E. Mandrak ◽  
E. J. Crossman
Keyword(s):  
North America ◽  
Freshwater Fishes ◽  
Eastern North America ◽  
Glacial Period ◽  
Before Present ◽  
Last Glacial Period ◽  
Historical Processes ◽  
Dispersal Routes ◽  
Atlantic Coastal ◽  
The Last Glacial

The present-day distributions of 117 native freshwater fishes in Ontario have been shaped by processes active following the Wisconsinan glacial period, 80 000–10 000 years before present. During this glacial period, these species survived in unglaciated réfugia. To understand the processes that resulted in the recolonization of Ontario by fishes following the last glacial period, the refugial areas occupied by each species were determined using a refugial index, and glacial water bodies used as dispersal routes were identified. The refugial origins of the Ontario populations of 91 species were resolved. Seventy-two species resided in the Mississippian refugium, 13 species in the Atlantic Coastal refugium, 4 species in dual Atlantic Coastal – Mississippian refugia, 1 species in a Missourian refugium, and 1 species in Atlantic Coastal, Mississippian, and Missourian refugia. These conclusions differed significantly from those of other studies. Five general patterns were identified from the distributions of 104 species. In addition, there are 13 species that do not fit any of the general patterns. Most species with similar distributions in Ontario shared the same refugia and dispersal routes in eastern North America, therefore it is hypothesized that historical processes were important in shaping the present-day distributions of Ontario freshwater fishes.

scholarly journals Transient climate simulations of the deglaciation 21–9 thousand years before present; PMIP4 Core experiment design and boundary conditions

2015 ◽  
Vol 8 (10) ◽  
pp. 9045-9102 ◽  
Author(s):  
R. F. Ivanovic ◽  
L. J. Gregoire ◽  
M. Kageyama ◽  
D. M. Roche ◽  
P. J. Valdes ◽  
...  
Keyword(s):  
Working Group ◽  
Ad Hoc ◽  
Climate Models ◽  
Ice Sheet ◽  
Before Present ◽  
Last Deglaciation ◽  
Transient Simulations ◽  
The Last Deglaciation ◽  
Set Up ◽  
Core Simulation

Abstract. The last deglaciation, which marked the transition between the last glacial and present interglacial periods, was punctuated by a series of rapid (centennial and decadal) climate changes. Numerical climate models are useful for investigating mechanisms that underpin the events, especially now that some of the complex models can be run for multiple millennia. We have set up a Paleoclimate Modelling Intercomparison Project (PMIP) working group to coordinate efforts to run transient simulations of the last deglaciation, and to facilitate the dissemination of expertise between modellers and those engaged with reconstructing the climate of the last 21 thousand years. Here, we present the design of a coordinated Core simulation over the period 21–9 thousand years before present (ka) with time varying orbital forcing, greenhouse gases, ice sheets, and other geographical changes. A choice of two ice sheet reconstructions is given, but no ice sheet or iceberg meltwater should be prescribed in the Core simulation. Additional focussed simulations will also be coordinated on an ad-hoc basis by the working group, for example to investigate the effect of ice sheet and iceberg meltwater, and the uncertainty in other forcings. Some of these focussed simulations will focus on shorter durations around specific events to allow the more computationally expensive models to take part.

scholarly journals CH<sub>4</sub> and N<sub>2</sub>O fluctuations during the penultimate deglaciation

2020 ◽  
Author(s):  
Loïc Schmidely ◽  
Christoph Nehrbass-Ahles ◽  
Jochen Schmitt ◽  
Juhyeong Han ◽  
Lucas Silva ◽  
...  
Keyword(s):  
Ice Core ◽  
Meridional Overturning Circulation ◽  
Trace Gas ◽  
Last Deglaciation ◽  
Last Glacial Period ◽  
Modes Of Variability ◽  
Present Composite ◽  
Meridional Overturning ◽  
The Last Deglaciation ◽  
Ch4 And N2o

Abstract. Deglaciations are characterized by the largest natural changes in methane (CH4) and nitrous oxide (N2O) concentrations of the past 800 thousand years. Reconstructions of millennial to centennial-scale variability within these periods are mostly restricted to the last deglaciation. In this study, we present composite records of CH4 and N2O concentrations from the EPICA Dome C ice core covering the penultimate deglaciation at temporal resolutions of about ~ 100 years. Our data permit the identification of centennial-scale fluctuations standing out of the overall transition to interglacial levels. These features occurred in concert with reinvigorations of the Atlantic Meridional Overturning Circulation (AMOC) and northward shifts of the Intertropical Convergence Zone. The abrupt CH4 and N2O rises at about ~ 134 and ~ 128 thousand of years before present (hereafter ka BP) are assimilated to the fluctuations accompanying the Dansgaard–Oeschger events of the last glacial period, while rising N2O levels at ~ 130.5 ka BP are assimilated to a pattern of increasing N2O concentrations that characterized the end of Heinrich stadials. We suggest the 130.5-ka event to be driven by a partial reinvigoration of the AMOC. Overall, the CH4 and N2O fluctuations during the penultimate deglaciation exhibit modes of variability that are also found during the last deglaciation. However, trace gas responses may differ for similar type of climatic events, as exemplified by the reduced amplitude and duration of the 134-ka event compared to the fluctuations of the Bølling–Allerød during the last deglaciation.

Pollen Diagram from the Nebraska Sandhills and the Age of the Dunes

1985 ◽  
Vol 24 (1) ◽  
pp. 115-120 ◽  
Author(s):  
H. E. Wright ◽  
J. C. Almendinger ◽  
J. Grüger
Keyword(s):  
Sand Dunes ◽  
Dune Sand ◽  
Last Glacial Period ◽  
Pollen Diagram ◽  
Radiocarbon Dates ◽  
The Holocene ◽  
Swan Lake ◽  
Nebraska Sandhills ◽  
Prairie Vegetation ◽  
The Last Glacial

Radiocarbon dates of organic alluvium beneath as much as 40 m of dune sand along the Dismal River have led to the suggestion that the Nebraska Sandhills date from the Holocene rather than the last glacial period. On the other hand, the basal layers of lake and marsh deposits in interdune depressions at three localities date in the range of 9000 to 12,000 yr B.P., implying a pre-Holocene age for the sand dunes. A pollen diagram for one of these sites, Swan Lake, indicates prairie vegetation throughout the last 9000 yr, with no suggestion that the landscape was barren enough to permit the shaping of the massive dunes characterizing the area. Sand was not transported across the site during the Holocene, either during the marsh phase, which lasted until 3700 yr B.P., or during the subsequent lake phase. The sand that buries the alluvium along the Dismal River may represent only local eolian activity, or it may indicate that the younger of the two main dune series identified by H. T. U. Smith (1965, Journal of Geology 73, 557–578) is Holocene in age, and the older one Late Wisconsin in age.

A 45 kyr laminae record from the Dead Sea: Implications for basin erosion and floods recurrence

2020 ◽  
Author(s):  
Nicolas Waldmann ◽  
Yin Lu ◽  
Revital Bookman ◽  
Shmulik Marco
Keyword(s):  
High Frequency ◽  
Lake Level ◽  
Dead Sea ◽  
Last Deglaciation ◽  
The Holocene ◽  
Lamina Thickness ◽  
The Last Deglaciation ◽  
The Dead ◽  
Basin Erosion ◽  
The Last Glacial

&lt;p&gt;Recording and analyzing how climate change impacts flood recurrence, basin erosion, and sedimentation can improve our understanding of these systems. The aragonite-detritus laminae couplets comprising the lacustrine formations that were deposited in the Dead Sea Basin are considered as faithful monitors of the freshwater supply to the lakes. We count a total of ~5600 laminae couplets deposited in the last 45 kyr (MIS3-MIS1) at the Dead Sea depocenter, which encompass the upper 141.6 m of the ICDP Core 5017-1. The present study shows that aragonite and detritus laminae are thinner and occur at high frequency during MIS 3-2, while they are much thicker and less frequent during MIS 1. By analyzing multiple climate-connected factors, we propose that significant lake-level drops, enhanced dust input, and low vegetative cover in the drainage basin during the last deglaciation (22-11.6 ka) have considerably increased erodible materials in the Dead Sea watershed. We find a decoupling existed between the significant lake-level drop/lake size reduction and lamina thickness change during the last deglaciation. We argue that during the last glacial and the Holocene, the variation of lamina thickness at the multiple-millennium scale was not controlled directly by the lake-level/size change. We interpret this decoupling implying the transport capacity of flash-floods is low and might be saturated by the oversupply of erodible materials, and indicating a transport-limited regime during the time period. We suggest that the observed thickness and frequency distribution of aragonite-detritus laminae points to the high frequency of small-magnitude floods during the last glacial period, in contrast to low frequency, but large-magnitude floods during the Holocene.&lt;/p&gt;

scholarly journals Cancelation of Deglacial Thermosteric Sea Level Rise by a Barosteric Effect

2020 ◽  
Vol 50 (12) ◽  
pp. 3623-3639
Author(s):  
Geoffrey Gebbie
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Steric Effect ◽  
Three Dimensional ◽  
Steric Effects ◽  
Last Deglaciation ◽  
Effect Analysis ◽  
Height Change ◽  
The Last Deglaciation ◽  
The Last Glacial

AbstractSea level rise over the last deglaciation is dominated by the mass of freshwater added to the oceans by the melting of the great ice sheets. While the steric effect of changing seawater density is secondary over the last 20 000 years, processes connected to deglacial warming, the redistribution of salt, and the pressure load of meltwater all influence sea level rise by more than a meter. Here we develop a diagnostic for steric effects that is valid when oceanic mass is changing. This diagnostic accounts for seawater compression due to the added overlying pressure of glacial meltwater, which is here defined to be a barosteric effect. Analysis of three-dimensional global seawater reconstructions of the last deglaciation indicates that thermosteric height change (1.0–1.5 m) is counteracted by barosteric (−1.9 m) and halosteric (from −0.4 to 0.0 m) effects. The total deglacial steric effect from −0.7 to −1.1 m has the opposite sign of analyses that assume that thermosteric expansion is dominant. Despite the vertical oceanic structure not being well constrained during the Last Glacial Maximum, net seawater contraction appears robust as it occurs in four reconstructions that were produced using different paleoceanographic datasets. Calculations that do not account for changes in ocean pressure give the misleading impression that steric effects enhanced deglacial sea level rise.

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