scholarly journals Relationship between meteoric <sup>10</sup>Be and NO<sub>3</sub><sup>−</sup> concentrations in soils along Shackleton Glacier, Antarctica

2021 ◽  
Vol 9 (5) ◽  
pp. 1363-1380
Author(s):  
Melisa A. Diaz ◽  
Lee B. Corbett ◽  
Paul R. Bierman ◽  
Byron J. Adams ◽  
Diana H. Wall ◽  
...  
Keyword(s):  
Spatial Scales ◽  
Polar Regions ◽  
Soil Evolution ◽  
Outlet Glacier ◽  
Soil Exposure ◽  
Order Of Magnitude ◽  
Flow Through ◽  
The Relationship ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Outlet glaciers that flow through the Transantarctic Mountains (TAM) experienced changes in ice thickness greater than other coastal regions of Antarctica during glacial maxima. As a result, ice-free areas that are currently exposed may have been covered by ice at various points during the Cenozoic, complicating our understanding of ecological succession in TAM soils. Our knowledge of glacial extent on small spatial scales is limited for the TAM, and studies of soil exposure duration and disturbance, in particular, are rare. We collected surface soil samples and, in some places, depth profiles every 5 cm to refusal (up to 30 cm) from 11 ice-free areas along Shackleton Glacier, a major outlet glacier of the East Antarctic Ice Sheet. We explored the relationship between meteoric 10Be and NO3- in these soils as a tool for understanding landscape disturbance and wetting history and as exposure proxies. Concentrations of meteoric 10Be spanned more than an order of magnitude across the region (2.9×108 to 73×108 atoms g−1) and are among the highest measured in polar regions. The concentrations of NO3- were similarly variable and ranged from ∼1 µg g−1 to 15 mg g−1. In examining differences and similarities in the concentrations of 10Be and NO3- with depth, we suggest that much of the southern portion of the Shackleton Glacier region has likely developed under a hyper-arid climate regime with minimal disturbance. Finally, we inferred exposure time using 10Be concentrations. This analysis indicates that the soils we analyzed likely range from recent exposure (following the Last Glacial Maximum) to possibly >6 Myr. We suggest that further testing and interrogation of meteoric 10Be and NO3- concentrations and relationships in soils can provide important information regarding landscape development, soil evolution processes, and inferred exposure durations of surfaces in the TAM.

scholarly journals The Relationship between ITCZ Location and Cross-Equatorial Atmospheric Heat Transport: From the Seasonal Cycle to the Last Glacial Maximum

2013 ◽  
Vol 26 (11) ◽  
pp. 3597-3618 ◽  
Author(s):  
Aaron Donohoe ◽  
John Marshall ◽  
David Ferreira ◽  
David Mcgee
Keyword(s):  
Seasonal Cycle ◽  
Climate Models ◽  
Regression Coefficient ◽  
Boreal Summer ◽  
Boreal Winter ◽  
Atmospheric Heat Transport ◽  
Atmospheric Heat ◽  
The Relationship ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract The authors quantify the relationship between the location of the intertropical convergence zone (ITCZ) and the atmospheric heat transport across the equator (AHTEQ) in climate models and in observations. The observed zonal mean ITCZ location varies from 5.3°S in the boreal winter to 7.2°N in the boreal summer with an annual mean position of 1.65°N while the AHTEQ varies from 2.1 PW northward in the boreal winter to 2.3 PW southward in the boreal summer with an annual mean of 0.1 PW southward. Seasonal variations in the ITCZ location and AHTEQ are highly anticorrelated in the observations and in a suite of state-of-the-art coupled climate models with regression coefficients of −2.7° and −2.4° PW−1 respectively. It is also found that seasonal variations in ITCZ location and AHTEQ are well correlated in a suite of slab ocean aquaplanet simulations with varying ocean mixed layer depths. However, the regression coefficient between ITCZ location and AHTEQ decreases with decreasing mixed layer depth as a consequence of the asymmetry that develops between the winter and summer Hadley cells as the ITCZ moves farther off the equator. The authors go on to analyze the annual mean change in ITCZ location and AHTEQ in an ensemble of climate perturbation experiments including the response to CO2 doubling, simulations of the Last Glacial Maximum, and simulations of the mid-Holocene. The shift in the annual average ITCZ location is also strongly anticorrelated with the change in annual mean AHTEQ with a regression coefficient of −3.2° PW−1, similar to that found over the seasonal cycle.

scholarly journals Effect of high dust amount on surface temperature during the Last Glacial Maximum: a modelling study using MIROC-ESM

2018 ◽  
Vol 14 (11) ◽  
pp. 1565-1581 ◽  
Author(s):  
Rumi Ohgaito ◽  
Ayako Abe-Ouchi ◽  
Ryouta O'ishi ◽  
Toshihiko Takemura ◽  
Akinori Ito ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Northern Hemisphere ◽  
Glacial Maximum ◽  
Polar Regions ◽  
Dust Deposition ◽  
Last Glacial ◽  
Radiative Perturbation ◽  
The Last Glacial Maximum ◽  
High Dust ◽  
The Last Glacial

Abstract. The effect of aerosols is one of many uncertain factors in projections of future climate. However, the behaviour of mineral dust aerosols (dust) can be investigated within the context of past climate change. The Last Glacial Maximum (LGM) is known to have had enhanced dust deposition in comparison with the present, especially over polar regions. Using the Model for Interdisciplinary Research on Climate Earth System Model (MIROC-ESM), we conducted a standard LGM experiment following the protocol of the Paleoclimate Modelling Intercomparison Project phase 3 and sensitivity experiments. We imposed glaciogenic dust on the standard LGM experiment and investigated the impacts of glaciogenic dust and non-glaciogenic dust on the LGM climate. Global mean radiative perturbations by glaciogenic and non-glaciogenic dust were both negative, consistent with previous studies. However, glaciogenic dust behaved differently in specific regions; e.g. it resulted in less cooling over the polar regions. One of the major reasons for reduced cooling is the ageing of snow or ice, which results in albedo reduction via high dust deposition, especially near sources of high glaciogenic dust emission. Although the net radiative perturbations in the lee of high glaciogenic dust provenances are negative, warming by the ageing of snow overcomes this radiative perturbation in the Northern Hemisphere. In contrast, the radiative perturbation due to high dust loading in the troposphere acts to warm the surface in areas surrounding Antarctica, primarily via the longwave aerosol–cloud interaction of dust, and it is likely the result of the greenhouse effect attributable to the enhanced cloud fraction in the upper troposphere. Although our analysis focused mainly on the results of experiments using the atmospheric part of the MIROC-ESM, we also conducted full MIROC-ESM experiments for an initial examination of the effect of glaciogenic dust on the oceanic general circulation module. A long-term trend of enhanced warming was observed in the Northern Hemisphere with increased glaciogenic dust; however, the level of warming around Antarctica remained almost unchanged, even after extended coupling with the ocean.

scholarly journals A new global ice sheet reconstruction for the past 80 000 years

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Evan J. Gowan ◽  
Xu Zhang ◽  
Sara Khosravi ◽  
Alessio Rovere ◽  
Paolo Stocchi ◽  
...  
Keyword(s):  
Sea Level ◽  
Ice Sheet ◽  
Far Field ◽  
Before Present ◽  
Ice Volume ◽  
The Past ◽  
Proxy Records ◽  
The Relationship ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractThe evolution of past global ice sheets is highly uncertain. One example is the missing ice problem during the Last Glacial Maximum (LGM, 26 000-19 000 years before present) – an apparent 8-28 m discrepancy between far-field sea level indicators and modelled sea level from ice sheet reconstructions. In the absence of ice sheet reconstructions, researchers often use marine δ18O proxy records to infer ice volume prior to the LGM. We present a global ice sheet reconstruction for the past 80 000 years, called PaleoMIST 1.0, constructed independently of far-field sea level and δ18O proxy records. Our reconstruction is compatible with LGM far-field sea-level records without requiring extra ice volume, thus solving the missing ice problem. However, for Marine Isotope Stage 3 (57 000-29 000 years before present) - a pre-LGM period - our reconstruction does not match proxy-based sea level reconstructions, indicating the relationship between marine δ18O and sea level may be more complex than assumed.

scholarly journals The effect of high dust amount on the surface temperature during the Last Glacial Maximum: A modelling study using MIROC-ESM

2018 ◽  
Author(s):  
Rumi Ohgaito ◽  
Ayako Abe-Ouchi ◽  
Ryouta O'ishi ◽  
Toshihiko Takemura ◽  
Akinori Ito ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Northern Hemisphere ◽  
Glacial Maximum ◽  
Polar Regions ◽  
Dust Deposition ◽  
Last Glacial ◽  
Radiative Perturbation ◽  
The Last Glacial Maximum ◽  
High Dust ◽  
The Last Glacial

Abstract. The effect of aerosols is one of the many uncertain factors in projections of the future climate. However, the behaviour of mineral dust aerosol (dust) can be investigated in the context of past climate changes. The Last Glacial Maximum (LGM) is known to have resulted in an enhancement of the dust deposition, especially over the polar regions. Using the Model for Interdisciplinary Research on Climate Earth System Model (MIROC-ESM), we investigated the impact of glaciogenic dust on the climate of the LGM and found that the effect of the enhancement of dust results in less cooling over the polar regions. One of the major reasons of the reduced cooling is the ageing of snow or ice, resulting in the reduction of the albedo by a high dust deposition, especially in the vicinity of high glaciogenic dust emissions. Although the net radiative perturbations in the lee of high glaciogenic dust provenances are negative, warming by ageing of snow overcomes this radiative perturbation in the Northern Hemisphere. In contrast, the radiative perturbation by the high dust loading in the troposphere acts to warm the surface surrounding Antarctica, which is mainly caused by the longwave aerosol–cloud interaction of dust and is likely the result of the greenhouse effect of the enhanced cloud fraction in the upper troposphere. Although our analysis mainly focused on the results of the experiments using the atmospheric part of the MIROC-ESM, we also conducted full MIROC-ESM experiments for a first trial of glacial dust modelling. The long-term trend to enhance warming in the Northern Hemisphere with the increase of glaciogenic dust was observed, whereas the warming level around Antarctica is almost unchanged, even after an extended interaction with the ocean.

scholarly journals An ice sheet model of reduced complexity for paleoclimate studies

2016 ◽  
Vol 7 (2) ◽  
pp. 397-418 ◽  
Author(s):  
Basil Neff ◽  
Andreas Born ◽  
Thomas F. Stocker
Keyword(s):  
Last Glacial Maximum ◽  
Computational Efficiency ◽  
Spatial Scales ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Model Parameters ◽  
Last Glacial ◽  
Reduced Complexity ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. IceBern2D is a vertically integrated ice sheet model to investigate the ice distribution on long timescales under different climatic conditions. It is forced by simulated fields of surface temperature and precipitation of the Last Glacial Maximum and present-day climate from a comprehensive climate model. This constant forcing is adjusted to changes in ice elevation. Due to its reduced complexity and computational efficiency, the model is well suited for extensive sensitivity studies and ensemble simulations on extensive temporal and spatial scales. It shows good quantitative agreement with standardized benchmarks on an artificial domain (EISMINT). Present-day and Last Glacial Maximum ice distributions in the Northern Hemisphere are also simulated with good agreement. Glacial ice volume in Eurasia is underestimated due to the lack of ice shelves in our model. The efficiency of the model is utilized by running an ensemble of 400 simulations with perturbed model parameters and two different estimates of the climate at the Last Glacial Maximum. The sensitivity to the imposed climate boundary conditions and the positive degree-day factor β, i.e., the surface mass balance, outweighs the influence of parameters that disturb the flow of ice. This justifies the use of simplified dynamics as a means to achieve computational efficiency for simulations that cover several glacial cycles. Hysteresis simulations over 5 million years illustrate the stability of the simulated ice sheets to variations in surface air temperature.

scholarly journals Relating pollen representation to an evolving Amazonian landscape between the last glacial maximum and Late Holocene

2020 ◽  
pp. 1-17
Author(s):  
Richard J. Smith ◽  
Francis E. Mayle ◽  
S. Yoshi Maezumi ◽  
Mitchell J. Power
Keyword(s):  
Last Glacial Maximum ◽  
Spatial Scales ◽  
Glacial Maximum ◽  
Fossil Pollen ◽  
Middle Holocene ◽  
Last Glacial ◽  
Riverine Forests ◽  
History Of ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract In contrast to temperate regions, relationships between basin characteristics (e.g., type/size) and fossil pollen archives have received little attention in Amazonia. Here, we compare fossil pollen records of a small palm swamp (Cuatro Vientos; CV) and a nearby large lake (Laguna Chaplin, LCH) in Bolivian Amazonia, demonstrating that palm swamps can yield Quaternary pollen archives recording the history of terrestrial vegetation beyond the basin margin, rather than merely a history of localized swamp vegetation dynamics. The pollen assemblages from these two contrasting basins display remarkable agreement throughout their late Quaternary history, indicating past drier climates supported savanna landscape during the last glacial maximum (LGM; 24,000–18,000 cal yr BP) and savanna/semideciduous forest mosaic during the middle Holocene (7000-4750 cal yr BP) at both regional (inferred from LCH) and local (inferred from CV) spatial scales. Additionally, the local-scale catchment of CV and the basin's proximity to the riverine forests of the Río Paraguá enables exploration of the extent of gallery/riverine forests during the LGM and middle Holocene. We show that, between 24,000–4000 cal yr BP, riverine/gallery rainforests were substantially reduced compared with present, challenging the hypothesis that gallery rainforests were important refugia for rainforest species during the drier LGM and middle Holocene.

scholarly journals Dynamics of Siberian Paleolithic Complexes (Based on Analysis of Radiocarbon Records): The 2012 State-of-the-Art

Radiocarbon ◽  
2013 ◽  
Vol 55 (3) ◽  
pp. 1314-1321 ◽  
Author(s):  
Yaroslav V Kuzmin ◽  
Susan G Keates
Keyword(s):  
Last Glacial Maximum ◽  
State Of The Art ◽  
Significant Decline ◽  
Glacial Maximum ◽  
Population Changes ◽  
Clear Trend ◽  
Last Glacial ◽  
The Relationship ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Our updated database of Siberian Paleolithic radiocarbon records (the 2011 date list of ∼800 values) was used to analyze the patterns of population changes, following the methodology developed previously (Kuzmin and Keates 2005). Although the main conclusions remain similar to our 2005 results, some new features were also detected. The intensity of occupation after ∼35,000–34,000 BP was higher than previously thought, and the rise in population began at ∼20,000–19,000 BP. It is once again confirmed that no significant decline can be observed for the Last Glacial Maximum (∼22,000–16,000 BP). The relationship between climate and Paleolithic humans in Siberia was complex and without a clear trend toward the intensification of occupation during the warm phases.

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