scholarly journals High latitude biospheric activity during the Last Glacial Cycle revealed by ammonium variations in Greenland Ice Cores

2001 ◽  
Vol 28 (22) ◽  
pp. 4239-4242 ◽  
Author(s):  
Margareta Hansson ◽  
Kim Holmén
Keyword(s):  
High Latitude ◽  
Ice Cores ◽  
Glacial Cycle ◽  
Last Glacial ◽  
The Last Glacial

scholarly journals Andean drought and glacial retreat tied to Greenland warming during the last glacial period

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Arielle Woods ◽  
Donald T. Rodbell ◽  
Mark B. Abbott ◽  
Robert G. Hatfield ◽  
Christine Y. Chen ◽  
...  
Keyword(s):  
Amazon Basin ◽  
Ice Cores ◽  
The Arctic ◽  
Glacier Mass Balance ◽  
Complete Disappearance ◽  
Tropical Andes ◽  
Glacial Cycle ◽  
Last Glacial ◽  
Isotopic Records ◽  
The Last Glacial

Abstract Abrupt warming events recorded in Greenland ice cores known as Dansgaard-Oeschger (DO) interstadials are linked to changes in tropical circulation during the last glacial cycle. Corresponding variations in South American summer monsoon (SASM) strength are documented, most commonly, in isotopic records from speleothems, but less is known about how these changes affected precipitation and Andean glacier mass balance. Here we present a sediment record spanning the last ~50 ka from Lake Junín (Peru) in the tropical Andes that has sufficient chronologic precision to document abrupt climatic events on a centennial-millennial time scale. DO events involved the near-complete disappearance of glaciers below 4700 masl in the eastern Andean cordillera and major reductions in the level of Peru’s second largest lake. Our results reveal the magnitude of the hydroclimatic disruptions in the highest reaches of the Amazon Basin that were caused by a weakening of the SASM during abrupt arctic warming. Accentuated warming in the Arctic could lead to significant reductions in the precipitation-evaporation balance of the southern tropical Andes with deleterious effects on this densely populated region of South America.

scholarly journals Numerical simulations of the Cordilleran ice sheet through the last glacial cycle

2016 ◽  
Vol 10 (2) ◽  
pp. 639-664 ◽  
Author(s):  
Julien Seguinot ◽  
Irina Rogozhina ◽  
Arjen P. Stroeven ◽  
Martin Margold ◽  
Johan Kleman
Keyword(s):  
Sediment Cores ◽  
Ice Sheet ◽  
Ice Cores ◽  
High Mountain ◽  
Glacial Cycle ◽  
Mountain Areas ◽  
Last Glacial ◽  
Proxy Records ◽  
Cordilleran Ice Sheet ◽  
The Last Glacial

Abstract. After more than a century of geological research, the Cordilleran ice sheet of North America remains among the least understood in terms of its former extent, volume, and dynamics. Because of the mountainous topography on which the ice sheet formed, geological studies have often had only local or regional relevance and shown such a complexity that ice-sheet-wide spatial reconstructions of advance and retreat patterns are lacking. Here we use a numerical ice sheet model calibrated against field-based evidence to attempt a quantitative reconstruction of the Cordilleran ice sheet history through the last glacial cycle. A series of simulations is driven by time-dependent temperature offsets from six proxy records located around the globe. Although this approach reveals large variations in model response to evolving climate forcing, all simulations produce two major glaciations during marine oxygen isotope stages 4 (62.2–56.9 ka) and 2 (23.2–16.9 ka). The timing of glaciation is better reproduced using temperature reconstructions from Greenland and Antarctic ice cores than from regional oceanic sediment cores. During most of the last glacial cycle, the modelled ice cover is discontinuous and restricted to high mountain areas. However, widespread precipitation over the Skeena Mountains favours the persistence of a central ice dome throughout the glacial cycle. It acts as a nucleation centre before the Last Glacial Maximum and hosts the last remains of Cordilleran ice until the middle Holocene (6.7 ka).

scholarly journals Ice-sheet modelling characteristics in sea-level-based temperature reconstructions over the last glacial cycle

2006 ◽  
Vol 52 (176) ◽  
pp. 149-158 ◽  
Author(s):  
Frank Wilschut ◽  
Richard Bintanja ◽  
Roderik S.W. Van De Wal
Keyword(s):  
Sea Level ◽  
Sediment Cores ◽  
Ice Sheet ◽  
Ice Cores ◽  
Glacial Cycle ◽  
Deep Sea Sediment ◽  
Last Glacial ◽  
Proxy Records ◽  
Temperature Reconstructions ◽  
The Last Glacial

AbstractA widely used method for investigating palaeotemperatures is to analyze local proxy records (e.g. ice cores or deep-sea sediment cores). The interpretation of these records is often not straightforward, and global or hemispheric means cannot be deduced from local estimates because of large spatial variability. Using a different approach, temperature changes over the last glacial cycle can be estimated from sea-level observations by applying an inverse method to an ice-sheet model. In order to understand the underlying physical mechanisms, we used a 1-D ice-sheet model and a 3-D coupled thermodynamic ice-sheet–ice-shelf–bedrock model to investigate the importance of several physical processes for the inverse temperature reconstructions. Results show that (i) temperature reconstructions are sensitive to the employed formulation of mass balance, (ii) excluding thermodynamics in the ice sheet leads to a smaller temperature amplitude in the reconstruction and (iii) hysteresis in the non-linear relation between sea level and temperature occurs as a consequence of ice redistribution in the process of merging and separation of ice sheets. The ice redistribution does not occur if the geometry does not support the formation of a relatively flat dome, which tends to be preserved in warming conditions.

Abrupt changes in high-latitude nutrient supply to the Atlantic during the last glacial cycle

Geology ◽  
2012 ◽  
Vol 40 (2) ◽  
pp. 123-126 ◽  
Author(s):  
K.R. Hendry ◽  
L.F. Robinson ◽  
M.P. Meredith ◽  
S. Mulitza ◽  
C.M. Chiessi ◽  
...  
Keyword(s):  
High Latitude ◽  
Nutrient Supply ◽  
Glacial Cycle ◽  
Last Glacial ◽  
Abrupt Changes ◽  
The Last Glacial

scholarly journals Widespread global peatland establishment and persistence over the last 130,000 y

2019 ◽  
Vol 116 (11) ◽  
pp. 4822-4827 ◽  
Author(s):  
Claire C. Treat ◽  
Thomas Kleinen ◽  
Nils Broothaerts ◽  
April S. Dalton ◽  
René Dommain ◽  
...  
Keyword(s):  
Ice Cores ◽  
C Sequestration ◽  
Quantitative Agreement ◽  
Glacial Cycle ◽  
Last Interglacial ◽  
Last Glacial ◽  
C Storage ◽  
C Stocks ◽  
Northern Peatlands ◽  
The Last Glacial

Glacial−interglacial variations in CO2 and methane in polar ice cores have been attributed, in part, to changes in global wetland extent, but the wetland distribution before the Last Glacial Maximum (LGM, 21 ka to 18 ka) remains virtually unknown. We present a study of global peatland extent and carbon (C) stocks through the last glacial cycle (130 ka to present) using a newly compiled database of 1,063 detailed stratigraphic records of peat deposits buried by mineral sediments, as well as a global peatland model. Quantitative agreement between modeling and observations shows extensive peat accumulation before the LGM in northern latitudes (>40°N), particularly during warmer periods including the last interglacial (130 ka to 116 ka, MIS 5e) and the interstadial (57 ka to 29 ka, MIS 3). During cooling periods of glacial advance and permafrost formation, the burial of northern peatlands by glaciers and mineral sediments decreased active peatland extent, thickness, and modeled C stocks by 70 to 90% from warmer times. Tropical peatland extent and C stocks show little temporal variation throughout the study period. While the increased burial of northern peats was correlated with cooling periods, the burial of tropical peat was predominately driven by changes in sea level and regional hydrology. Peat burial by mineral sediments represents a mechanism for long-term terrestrial C storage in the Earth system. These results show that northern peatlands accumulate significant C stocks during warmer times, indicating their potential for C sequestration during the warming Anthropocene.

scholarly journals Numerical simulations of the Cordilleran ice sheet through the last glacial cycle

2015 ◽  
Vol 9 (4) ◽  
pp. 4147-4203 ◽  
Author(s):  
J. Seguinot ◽  
I. Rogozhina ◽  
A. P. Stroeven ◽  
M. Margold ◽  
J. Kleman
Keyword(s):  
Sediment Cores ◽  
Ice Sheet ◽  
Ice Cores ◽  
High Mountain ◽  
Glacial Cycle ◽  
Mountain Areas ◽  
Last Glacial ◽  
Proxy Records ◽  
Cordilleran Ice Sheet ◽  
The Last Glacial

Abstract. Despite more than a century of geological observations, the Cordilleran ice sheet of North America remains poorly understood in terms of its former extent, volume and dynamics. Although geomorphological evidence is abundant, its complexity is such that whole ice-sheet reconstructions of advance and retreat patterns are lacking. Here we use a numerical ice sheet model calibrated against field-based evidence to attempt a quantitative reconstruction of the Cordilleran ice sheet history through the last glacial cycle. A series of simulations is driven by time-dependent temperature offsets from six proxy records located around the globe. Although this approach reveals large variations in model response to evolving climate forcing, all simulations produce two major glaciations during marine oxygen isotope stages 4 (61.9–56.5 ka) and 2 (23.2–16.8 ka). The timing of glaciation is better reproduced using temperature reconstructions from Greenland and Antarctic ice cores than from regional oceanic sediment cores. During most of the last glacial cycle, the modelled ice cover is discontinuous and restricted to high mountain areas. However, widespread precipitation over the Skeena Mountains favours the persistence of a central ice dome throughout the glacial cycle. It acts as a nucleation centre before the Last Glacial Maximum and hosts the last remains of Cordilleran ice until the middle Holocene (6.6–6.2 ka).

A spatio-temporal view of variability in pollen records during the last Glacial

2020 ◽  
Author(s):  
Nils Weitzel ◽  
Moritz Adam ◽  
Anna Sommani ◽  
Kira Rehfeld
Keyword(s):  
Climate Variability ◽  
Ice Cores ◽  
Global Network ◽  
Glacial Cycle ◽  
Climate Signal ◽  
Last Glacial ◽  
Additional Information ◽  
Climate Simulations ◽  
Pollen Records ◽  
The Last Glacial

<p>Climate variability influences the probability of extreme events and is therefore of great importance for risk management. Nevertheless, changes in climate variability over time are far less studied than changes in the mean state of the climate system. Proxy records can be used to estimate the dependency of climate variability on the state and timescale, but their climate signal is perturbed by non-climatic processes and dating uncertainties. Analyzing ice cores and marine sediments, it was shown that temperature variability during the Last Glacial Maximum was larger than in the Holocene and that the magnitude of variability change depends on latitude.</p><p>We estimate millennial and orbital scale variability in pollen records during the last Glacial. We draw on a global network of published pollen records, which are influenced by local temperature and moisture availability, and compare these estimates with temperature, precipitation, and vegetation variability in climate simulations of the last Glacial cycle. We discuss the regional consistency of timescale dependent estimates. Differences between Marine Isotope Stages 2, 3, and 4 are examined by comparing spatial patterns during those three periods. Then, we use spectral methods to study the scaling behavior of the pollen records. This provides additional information on the continuum of variability from centennial to orbital scales. Finally, we quantify the co-occurrence of millennial and orbital scale fluctuations across different pollen records with paleoclimate network techniques.</p><p>Our work extends previous estimates to the terrestrial realm and to longer timescales. The results provide new insight on the climate variability differences between glacial and interglacial states, and on the mismatch between climate simulations and proxy data.</p>

scholarly journals Speleothem Records of the Hydroclimate Variability throughout the Last Glacial Cycle from Manita peć Cave (Velebit Mountain, Croatia)

Geosciences ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 347
Author(s):  
Maša Surić ◽  
Petra Bajo ◽  
Robert Lončarić ◽  
Nina Lončar ◽  
Russell N. Drysdale ◽  
...  
Keyword(s):  
Sea Level ◽  
Environmental Changes ◽  
Carbonic Acid ◽  
Precipitation Amount ◽  
Specific Effect ◽  
Ice Cores ◽  
Glacial Cycle ◽  
Last Glacial ◽  
Mis 3 ◽  
The Last Glacial

We present stable carbon (δ13C) and oxygen (δ18O) isotope records from two partially coeval speleothems from Manita peć Cave, Croatia. The cave is located close to the Adriatic coast (3.7 km) at an elevation of 570 m a.s.l. The site experienced competing Mediterranean and continental climate influences throughout the last glacial cycle and was situated close to the ice limit during the glacial phases. U-Th dating constrains the growth history from Marine Isotope Stage (MIS) 5 to MIS 3 and the transition from MIS 2 to MIS 1. 14C dating was used to estimate the age of the youngest part of one stalagmite found to be rich in detrital thorium and thus undatable by U-Th. On a millennial scale, δ18O variations partly mimic the Dansgaard–Oeschger interstadials recorded in Greenland ice cores (Greenland Interstadials, GI) from GI 22 to GI 13. We interpret our δ18O record as a proxy for variations in precipitation amount and/or moisture sources, and the δ13C record is interpreted as a proxy for changes in soil bioproductivity. The latter indicates a generally reduced vegetation cover towards MIS 3–MIS 4, with shifts of ~8‰ and approaching values close to those of the host rock. However, even during the coldest phases, when a periglacial setting and enhanced aridity sustained long-residence-time groundwater, carbonic-acid dissolution remains the driving force of the karstification processes. Speleothem morphology follows changes in environmental conditions and complements regional results of submerged speleothems findings. Specifically, narrow sections of light porous spelaean calcite precipitated during the glacial/stadial sea-level lowstands, while the warmer and wetter conditions were marked with compact calcite and hiatuses in submerged speleothems due to sea-level highstands. Presumably, the transformation of this littoral site to a continental one with somewhat higher amounts of orographic precipitation was a site-specific effect that masked regional environmental changes.

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