scholarly journals Modelling the diversion of erratic boulders by the Valais Glacier during the last glacial maximum

2017 ◽  
Vol 63 (239) ◽  
pp. 487-498 ◽  
Author(s):  
GUILLAUME JOUVET ◽  
JULIEN SEGUINOT ◽  
SUSAN IVY-OCHS ◽  
MARTIN FUNK
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Balance Model ◽  
Precipitation Pattern ◽  
Climate Data ◽  
Surface Mass ◽  
Climate Conditions ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

ABSTRACTIn this study, a modelling approach was used to investigate the cause of the diversion of erratic boulders from Mont Blanc and southern Valais by the Valais Glacier to the Solothurn lobe during the Last Glacial Maximum (LGM). Using the Parallel Ice Sheet Model, we simulated the ice flow field during the LGM, and analyzed the trajectories taken by erratic boulders from areas with characteristic lithologies. The main difficulty in this exercise laid with the large uncertainties affecting the paleo climate forcing required as input for the surface mass-balance model. In order to mimic the prevailing climate conditions during the LGM, we applied different temperature offsets and regional precipitation corrections to present-day climate data, and selected the parametrizations, which yielded the best match between the modelled ice extent and the geomorphologically-based ice-margin reconstruction. After running a range of simulations with varying parameters, our results showed that only one parametrization allowed boulders to be diverted to the Solothurn lobe during the LGM. This precipitation pattern supports the existing theory of preferential southwesterly advection of moisture to the alps during the LGM, but also indicates strongly enhanced precipitation over the Mont Blanc massif and enhanced cooling over the Jura Mountains.

Exploring the complex uncertainties in coupled climate-ice simulations of the Last Glacial Maximum

2021 ◽  
Author(s):  
Lauren Gregoire ◽  
Niall Gandy ◽  
Lachlan Astfalck ◽  
Robin Smith ◽  
Ruza Ivanovic ◽  
...  
Keyword(s):  
Mass Balance ◽  
Last Glacial Maximum ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Sea Surface ◽  
Surface Mass ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>Simulating the co-evolution of climate and ice-sheets during the Quaternary is key to understanding some of the major abrupt changes in climate, ice and sea level. Indeed, events such as the Meltwater pulse 1a rapid sea level rise and Heinrich, Dansgaard–Oeschger and the 8.2 kyr climatic events all involve the interplay between ice sheets, the atmosphere and the ocean. Unfortunately, it is challenging to simulate the coupled Climate-Ice sheet system because small biases, errors or uncertainties in parts of the models are strongly amplified by the powerful interactions between the atmosphere and ice (e.g. ice-albedo and height-mass balance feedbacks). This leads to inaccurate or even unrealistic simulations of ice sheet extent and surface climate. To overcome this issue we need some methods to effectively explore the uncertainty in the complex Climate-Ice sheet system and reduce model biases. Here we present our approach to produce ensemble of coupled Climate-Ice sheet simulations of the Last Glacial maximum that explore the uncertainties in climate and ice sheet processes.</p><p>We use the FAMOUS-ICE earth system model, which comprises a coarse-resolution and fast general circulation model coupled to the Glimmer-CISM ice sheet model. We prescribe sea surface temperature and sea ice concentrations in order to control and reduce biases in polar climate, which strongly affect the surface mass balance and simulated extent of the northern hemisphere ice sheets. We develop and apply a method to reconstruct and sample a range of realistic sea surface temperature and sea-ice concentration spatio-temporal field. These are created by merging information from PMIP3/4 climate simulations and proxy-data for sea surface temperatures at the Last Glacial Maximum with Bayes linear analysis. We then use these to generate ensembles of FAMOUS-ice simulations of the Last Glacial maximum following the PMIP4 protocol, with the Greenland and North American ice sheets interactively simulated. In addition to exploring a range of sea surface conditions, we also vary key parameters that control the surface mass balance and flow of ice sheets. We thus produce ensembles of simulations that will later be used to emulate ice sheet surface mass balance.  </p>

scholarly journals The effect of a dynamic soil scheme on the climate of the mid-Holocene and the Last Glacial Maximum

2016 ◽  
Vol 12 (1) ◽  
pp. 151-170 ◽  
Author(s):  
M. Stärz ◽  
G. Lohmann ◽  
G. Knorr
Keyword(s):  
Last Glacial Maximum ◽  
Positive Feedback ◽  
Climate Model ◽  
Soil Characteristics ◽  
Glacial Maximum ◽  
Balance Model ◽  
Primary Control ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. In order to account for coupled climate–soil processes, we have developed a soil scheme which is asynchronously coupled to a comprehensive climate model with dynamic vegetation. This scheme considers vegetation as the primary control of changes in physical soil characteristics. We test the scheme for a warmer (mid-Holocene) and colder (Last Glacial Maximum) climate relative to the preindustrial climate. We find that the computed changes in physical soil characteristics lead to significant amplification of global climate anomalies, representing a positive feedback. The inclusion of the soil feedback yields an extra surface warming of 0.24 °C for the mid-Holocene and an additional global cooling of 1.07 °C for the Last Glacial Maximum. Transition zones such as desert–savannah and taiga–tundra exhibit a pronounced response in the model version with dynamic soil properties. Energy balance model analyses reveal that our soil scheme amplifies the temperature anomalies in the mid-to-high northern latitudes via changes in the planetary albedo and the effective longwave emissivity. As a result of the modified soil treatment and the positive feedback to climate, part of the underestimated mid-Holocene temperature response to orbital forcing can be reconciled in the model.

Paleo-climate of the central European uplands during the last glacial maximum based on glacier mass-balance modeling

2013 ◽  
Vol 79 (1) ◽  
pp. 49-54 ◽  
Author(s):  
Barbara M. Heyman ◽  
Jakob Heyman ◽  
Thomas Fickert ◽  
Jonathan M. Harbor
Keyword(s):  
Mass Balance ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Balance Model ◽  
Glacier Mass Balance ◽  
Central European ◽  
Last Glacial ◽  
Vosges Mountains ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractDuring the last glacial maximum (LGM), glaciers existed in scattered mountainous locations in central Europe between the major ice masses of Fennoscandia and the Alps. A positive degree-day glacier mass-balance model is used to constrain paleo-climate conditions associated with reconstructed LGM glacier extents of four central European upland regions: the Vosges Mountains, the Black Forest, the Bavarian Forest, and the Giant Mountains. With reduced precipitation (25–75%), reflecting a drier LGM climate, the modeling yields temperature depressions of 8–15°C. To reproduce past glaciers more severe cooling is required in the west than in the east, indicating a strong west–east temperature anomaly gradient.

scholarly journals Analysis of the global atmospheric methane budget using ECHAM-MOZ simulations for present-day, pre-industrial time and the Last Glacial Maximum

2014 ◽  
Vol 14 (2) ◽  
pp. 3193-3230 ◽  
Author(s):  
A. Basu ◽  
M. G. Schultz ◽  
S. Schröder ◽  
L. Francois ◽  
X. Zhang ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Anthropogenic Sources ◽  
Atmospheric Methane ◽  
Climate Conditions ◽  
Last Glacial ◽  
Methane Budget ◽  
The Last Glacial Maximum ◽  
Methane Concentrations ◽  
The Last Glacial

Abstract. Atmospheric methane concentrations increased considerably from pre-industrial (PI) to present times largely due to anthropogenic emissions. However, firn and ice core records also document a notable rise of methane levels between the Last Glacial Maximum (LGM) and the pre-industrial era, the exact cause of which is not entirely clear. This study investigates these changes by analyzing the methane sources and sinks at each of these climatic periods. Wetlands are the largest natural source of methane and play a key role in determining methane budget changes in particular in the absence of anthropogenic sources. Here, a simple wetland parameterization suitable for coarse-scale climate simulations over long periods is introduced, which is derived from a high-resolution map of surface slopes together with various soil hydrology parameters from the CARAIB vegetation model. This parameterization was implemented in the chemistry general circulation model ECHAM5-MOZ and multi-year time slices were run for LGM, PI and present-day (PD) climate conditions. Global wetland emissions from our parameterization are 72 Tg yr−1 (LGM), 115 Tg yr−1 (PI), and 132 Tg yr−1 (PD). These estimates are lower than most previous studies, and we find a stronger increase of methane emissions between LGM and PI. Taking into account recent findings that suggest more stable OH concentrations than assumed in previous studies, the observed methane distributions are nevertheless well reproduced under the different climates. Hence, this is one of the first studies where a consistent model approach has been successfully applied for simulating methane concentrations over a wide range of climate conditions.

scholarly journals Supplemental Material: Climate of the Last Glacial Maximum on the western Olympic Peninsula based on insect paleoecology

2020 ◽  
Author(s):  
Allan Ashworth ◽  
et al.
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Fossil Insects ◽  
Climate Data ◽  
Model Data ◽  
Olympic Peninsula ◽  
Last Glacial ◽  
Fossil Insect ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Age-depth model data, images of fossil insect and plant macroscopic remains, lists of skeletal elements for fossil insects, and locality and derived climate data for Olophrum boreale and Olophrum consimile<br>

scholarly journals A Phytolith Supported Biosphere-Hydrosphere Predictive Model for Southern Ethiopia: Insights into Paleoenvironmental Changes and Human Landscape Preferences since the Last Glacial Maximum

Geosciences ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 418
Author(s):  
Markus L. Fischer ◽  
Felix Bachofer ◽  
Chad L. Yost ◽  
Ines J. E. Bludau ◽  
Christian Schepers ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Balance Model ◽  
Southern Ethiopia ◽  
Last Glacial ◽  
Landcover Change ◽  
Moisture Availability ◽  
Dry Conditions ◽  
The Last Glacial Maximum ◽  
The Last Glacial

During the past 25 ka, southern Ethiopia has undergone tremendous climatic changes, from dry and relatively cold during the Last Glacial Maximum (LGM, 25–18 ka) to the African Humid Period (AHP, 15–5 ka), and back to present-day dry conditions. As a contribution to better understand the effects of climate change on vegetation and lakes, we here present a new Predictive Vegetation Model that is linked with a Lake Balance Model and available vegetation-proxy records from southern Ethiopia including a new phytolith record from the Chew Bahir basin. We constructed a detailed paleo-landcover map of southern Ethiopia during the LGM, AHP (with and without influence of the Congo Air Boundary) and the modern-day potential natural landcover. Compared to today, we observe a 15–20% reduction in moisture availability during the LGM with widespread open landscapes and only few remaining forest refugia. We identify 25–40% increased moisture availability during the AHP with prevailing forests in the mid-altitudes and indications that modern anthropogenic landcover change has affected the water balance. In comparison with existing archaeological records, we find that human occupations tend to correspond with open landscapes during the late Pleistocene and Holocene in southern Ethiopia.

scholarly journals Supplemental Material: Climate of the Last Glacial Maximum on the western Olympic Peninsula based on insect paleoecology

2020 ◽  
Author(s):  
Allan Ashworth ◽  
et al.
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Fossil Insects ◽  
Climate Data ◽  
Model Data ◽  
Olympic Peninsula ◽  
Last Glacial ◽  
Fossil Insect ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Age-depth model data, images of fossil insect and plant macroscopic remains, lists of skeletal elements for fossil insects, and locality and derived climate data for Olophrum boreale and Olophrum consimile<br>

scholarly journals Gridded climate data from 5 GCMs of the Last Glacial Maximum downscaled to 30 arc s for Europe

2015 ◽  
Vol 11 (3) ◽  
pp. 2585-2613 ◽  
Author(s):  
D. R. Schmatz ◽  
J. Luterbacher ◽  
N. E. Zimmermann ◽  
P. B. Pearman
Keyword(s):  
High Resolution ◽  
Sea Level ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Baseline Data ◽  
Climate Data ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
Very High ◽  
The Last Glacial

Abstract. Studies of the impacts of historical, current and future global change require very high-resolution climate data (≤ 1 km) as a basis for modelled responses, meaning that data from digital climate models generally require substantial rescaling. Another shortcoming of available datasets on past climate is that the effects of sea level rise and fall are not considered. Without such information, the study of glacial refugia or early Holocene plant and animal migration are incomplete if not impossible. Sea level at the last glacial maximum (LGM) was approximately 125 m lower, creating substantial additional terrestrial area for which no current baseline data exist. Here, we introduce the development of a novel, gridded climate dataset for LGM that is both very high resolution (1 km) and extends to the LGM sea and land mask. We developed two methods to extend current terrestrial precipitation and temperature data to areas between the current and LGM coastlines. The absolute interpolation error is less than 1 and 0.5 °C for 98.9 and 87.8 %, respectively, of all pixels within two arc degrees of the current coastline. We use the change factor method with these newly assembled baseline data to downscale five global circulation models of LGM climate to a resolution of 1 km for Europe. As additional variables we calculate 19 "bioclimatic" variables, which are often used in climate change impact studies on biological diversity. The new LGM climate maps are well suited for analysing refugia and migration during Holocene warming following the LGM.

scholarly journals Simulated Impact of the Tibetan Glacier Expansion on the Eurasian Climate and Glacial Surface Mass Balance during the Last Glacial Maximum

2020 ◽  
Vol 33 (15) ◽  
pp. 6491-6509 ◽  
Author(s):  
Yonggang Liu ◽  
Yubin Wu ◽  
Zhongda Lin ◽  
Yang Zhang ◽  
Jiang Zhu ◽  
...  
Keyword(s):  
Mass Balance ◽  
Last Glacial Maximum ◽  
Summer Precipitation ◽  
Glacial Maximum ◽  
Surface Mass Balance ◽  
The Tibetan Plateau ◽  
Surface Mass ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract Glaciers over the Tibetan Plateau and surrounding regions during the Last Glacial Maximum (LGM) were much more extensive than during the preindustrial period (PI). The climate impact of such glacial expansion is studied here using the Community Atmosphere Model, version 4 (CAM4). To cover the range of uncertainty in glacier area during the LGM, the following three values are tested: 0.35 × 106, 0.53 × 106, and 0.70 × 106 km2. The added glacier is distributed approximately equally over the Pamir region and the Himalayas. If 0.70 × 106 km2 is used, the annual mean surface temperature of the glaciated regions would be cooled by ~3.5°C. The annual mean precipitation would be reduced by 0.2 mm day−1 (10%) and 2.5 mm day−1 (24%) over the Pamir region and Himalayas, respectively. The surface mass balance (SMB) of the glaciers changes by 0.55 m yr−1 (280%) and −0.32 m yr−1 (−20%) over the two regions, respectively. The changes in SMB remain large (0.29 and −0.13 m yr−1), even if the area of the Tibetan glacier were 0.35 × 106 km2. Therefore, based on the results of this particular model, the expansion of glaciers can either enhance or slow the glacial growth. Moreover, the expansion of glaciers over the Himalayas reduces summer precipitation in central and northern China by ~0.5 mm day−1 and increases summer precipitation in southern Asia by ~0.6 mm day−1. The expansion of glaciers over the Pamir region has a negligible influence on the precipitation in these monsoonal regions, which is likely due to its large distance from the main monsoonal regions.

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