A high-resolution record of vegetation and climate through the last glacial cycle from Caledonia Fen, southeastern highlands of Australia

AbstractPrevious paleoceanographic studies along the NW African margin focused on the dynamics of surface and intermediate waters, whereas little attention has been devoted to deep-water masses. Currently, these deep waters consist mainly of North Atlantic Deep Waters as part of the Atlantic Meridional Overturning Circulation (AMOC). However, this configuration was altered during periods of AMOC collapse. We present a high-resolution reconstruction of bottom-water ventilation and current evolution off Mauritania from the last glacial maximum into the early Holocene. Applying redox proxies (Mo, U and Mn) measured on sediments from off Mauritania, we describe changes in deep-water oxygenation and we infer the evolution of deep-water conditions during millennial-scale climate/oceanographic events in the area. The second half of Heinrich Event 1 and the Younger Dryas were recognized as periods of reduced ventilation, coinciding with events of AMOC reduction. We propose that these weakening circulation events induced deficient deep-water oxygenation in the Mauritanian upwelling region, which together with increased productivity promoted reducing conditions and enhanced organic-matter preservation. This is the first time the effect of AMOC collapse in the area is described at high resolution, broadening the knowledge on basin-wide oceanographic changes associated with rapid climate variability during the last deglaciation.

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Detailed spatially distributed geothermal heat-flow data for modeling of basal temperatures and meltwater production beneath the Fennoscandian ice sheet

Annals of Glaciology ◽

10.3189/172756405781813582 ◽

2005 ◽

Vol 40 ◽

pp. 95-101 ◽

Cited By ~ 29

Author(s):

Jens-Ove Näslund ◽

Peter Jansson ◽

James L. Fastook ◽

Jesse Johnson ◽

Leif Andersson

Keyword(s):

High Resolution ◽

Heat Flow ◽

Ice Sheets ◽

Ice Sheet ◽

Flow Density ◽

Glacial Cycle ◽

Geothermal Heat ◽

Last Glacial ◽

Uniform Value ◽

The Last Glacial

AbstractAccurate modeling of ice sheets requires proper information on boundary conditions, including the geothermal heat flow (or heat-flow density (HFD)). Traditionally, one uniform HFD value is adopted for the entire modeled domain. We have calculated a distributed, high-resolution HFD dataset for an approximate core area (Sweden and Finland) of the Scandinavian ice sheet, and imbedded this within lower-resolution data published for surrounding regions. Within the Last Glacial Maximum ice margin, HFD varies with a factor of as much as 2.8 (HFD values ranging between 30 and 83 mWm–2), with an average of 49 mWm–2. This average value is 17% higher than 42 mWm–2, a common uniform value used in ice-sheet modeling studies of Fennoscandia. Using this new distributed dataset on HFD, instead of a traditional uniform value of 42 mWm–2, yields a 1.4 times larger total basal meltwater production for the last glacial cycle. Furthermore, using the new dataset in high-resolution modeling results in increased spatial thermal gradients at the bed. This enhances and introduces new local and regional effects on basal ice temperatures and melt rates. We observed significant strengthening of local ‘ice streaming’, which in one case correlates to an ice-flow event previously interpreted from geomorphology. Regional to local variations in geothermal heat flow need to be considered for proper identification and treatment of thermal and hydraulic bed conditions, most likely also when studying Laurentide, Greenland and Antarctic ice sheets.

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Millennial-scale atmospheric CO<sub>2</sub> variations during the Marine Isotope Stage 6 period (190–135 ka)

Climate of the Past ◽

10.5194/cp-16-2203-2020 ◽

2020 ◽

Vol 16 (6) ◽

pp. 2203-2219

Author(s):

Jinhwa Shin ◽

Christoph Nehrbass-Ahles ◽

Roberto Grilli ◽

Jai Chowdhry Beeman ◽

Frédéric Parrenin ◽

...

Keyword(s):

High Resolution ◽

Northern Hemisphere ◽

Marine Isotope Stage ◽

Atmospheric Co2 ◽

Temperature Record ◽

Glacial Period ◽

Glacial Cycle ◽

High Resolution Data ◽

Last Glacial ◽

The Last Glacial

Abstract. Using new and previously published CO2 data from the EPICA Dome C ice core (EDC), we reconstruct a new high-resolution record of atmospheric CO2 during Marine Isotope Stage (MIS) 6 (190 to 135 ka) the penultimate glacial period. Similar to the last glacial cycle, where high-resolution data already exists, our record shows that during longer North Atlantic (NA) stadials, millennial CO2 variations during MIS 6 are clearly coincident with the bipolar seesaw signal in the Antarctic temperature record. However, during one short stadial in the NA, atmospheric CO2 variation is small (∼5 ppm) and the relationship between temperature variations in EDC and atmospheric CO2 is unclear. The magnitude of CO2 increase during Carbon Dioxide Maxima (CDM) is closely related to the NA stadial duration in both MIS 6 and MIS 3 (60–27 ka). This observation implies that during the last two glacials the overall bipolar seesaw coupling of climate and atmospheric CO2 operated similarly. In addition, similar to the last glacial period, CDM during the earliest MIS 6 show different lags with respect to the corresponding abrupt CH4 rises, the latter reflecting rapid warming in the Northern Hemisphere (NH). During MIS 6i at around 181.5±0.3 ka, CDM 6i lags the abrupt warming in the NH by only 240±320 years. However, during CDM 6iv (171.1±0.2 ka) and CDM 6iii (175.4±0.4 ka) the lag is much longer: 1290±540 years on average. We speculate that the size of this lag may be related to a larger expansion of carbon-rich, southern-sourced waters into the Northern Hemisphere in MIS 6, providing a larger carbon reservoir that requires more time to be depleted.

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A NEW METHOD TO SIMULATE THE ANTARCTIC ICE SHEET OVER THE LAST GLACIAL CYCLE USING A COUPLED 3D GIA – ICE DYNAMIC MODEL

10.1130/abs/2020am-359854 ◽

2020 ◽

Author(s):

C.J. van Calcar ◽

◽

B. de Boer ◽

B. Blank ◽

W. van der Wal

Keyword(s):

Dynamic Model ◽

Ice Sheet ◽

New Method ◽

Glacial Cycle ◽

Antarctic Ice Sheet ◽

Last Glacial ◽

The Antarctic ◽

The Last Glacial

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Effects of glaciation on karst hydrology and sedimentology during the Last Glacial Cycle: The case of Granito cave, Central Pyrenees (Spain)

CATENA ◽

10.1016/j.catena.2021.105252 ◽

2021 ◽

Vol 206 ◽

pp. 105252

Author(s):

Miguel Bartolomé ◽

Carlos Sancho ◽

Gerardo Benito ◽

Alicia Medialdea ◽

Mikel Calle ◽

...

Keyword(s):

Karst Hydrology ◽

Glacial Cycle ◽

Last Glacial ◽

Central Pyrenees ◽

The Last Glacial

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Drivers of river reactivation in North Africa during the last glacial cycle

Nature Geoscience ◽

10.1038/s41561-020-00671-3 ◽

2021 ◽

Vol 14 (2) ◽

pp. 97-103

Author(s):

Cécile L. Blanchet ◽

Anne H. Osborne ◽

Rik Tjallingii ◽

Werner Ehrmann ◽

Tobias Friedrich ◽

...

Keyword(s):

North Africa ◽

Glacial Cycle ◽

Last Glacial ◽

The Last Glacial

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Carbon burial in deep-sea sediment and implications for oceanic inventories of carbon and alkalinity over the last glacial cycle

Climate of the Past ◽

10.5194/cp-14-1819-2018 ◽

2018 ◽

Vol 14 (11) ◽

pp. 1819-1850 ◽

Cited By ~ 11

Author(s):

Olivier Cartapanis ◽

Eric D. Galbraith ◽

Daniele Bianchi ◽

Samuel L. Jaccard

Keyword(s):

Marine Sediments ◽

Active Carbon ◽

Deep Sea ◽

Dissolved Inorganic Carbon ◽

Glacial Cycle ◽

Last Glacial ◽

Carbon Burial ◽

Order Constraint ◽

The Last Glacial ◽

Carbon Inventory

Abstract. Although it has long been assumed that the glacial–interglacial cycles of atmospheric CO2 occurred due to increased storage of CO2 in the ocean, with no change in the size of the “active” carbon inventory, there are signs that the geological CO2 supply rate to the active pool varied significantly. The resulting changes of the carbon inventory cannot be assessed without constraining the rate of carbon removal from the system, which largely occurs in marine sediments. The oceanic supply of alkalinity is also removed by the burial of calcium carbonate in marine sediments, which plays a major role in air–sea partitioning of the active carbon inventory. Here, we present the first global reconstruction of carbon and alkalinity burial in deep-sea sediments over the last glacial cycle. Although subject to large uncertainties, the reconstruction provides a first-order constraint on the effects of changes in deep-sea burial fluxes on global carbon and alkalinity inventories over the last glacial cycle. The results suggest that reduced burial of carbonate in the Atlantic Ocean was not entirely compensated by the increased burial in the Pacific basin during the last glacial period, which would have caused a gradual buildup of alkalinity in the ocean. We also consider the magnitude of possible changes in the larger but poorly constrained rates of burial on continental shelves, and show that these could have been significantly larger than the deep-sea burial changes. The burial-driven inventory variations are sufficiently large to have significantly altered the δ13C of the ocean–atmosphere carbon and changed the average dissolved inorganic carbon (DIC) and alkalinity concentrations of the ocean by more than 100 µM, confirming that carbon burial fluxes were a dynamic, interactive component of the glacial cycles that significantly modified the size of the active carbon pool. Our results also suggest that geological sources and sinks were significantly unbalanced during the late Holocene, leading to a slow net removal flux on the order of 0.1 PgC yr−1 prior to the rapid input of carbon during the industrial period.

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