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.

scholarly journals Clumped isotope constraints on changes in latest Pleistocene hydroclimate in the northwestern Great Basin: Lake Surprise, California

2020 ◽  
Vol 132 (11-12) ◽  
pp. 2669-2683
Author(s):  
L.M. Santi ◽  
A.J. Arnold ◽  
D.E. Ibarra ◽  
C.A. Whicker ◽  
J.A. Mering ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Great Basin ◽  
Climate Model ◽  
Glacial Maximum ◽  
Model Simulations ◽  
Last Glacial ◽  
Climate Forcings ◽  
Clumped Isotope ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract During the Last Glacial Maximum (LGM) and subsequent deglaciation, the Great Basin in the southwestern United States was covered by numerous extensive closed-basin lakes, in stark contrast with the predominately arid climate observed today. This transition from lakes in the Late Pleistocene to modern aridity implies large changes in the regional water balance. Whether these changes were driven by increased precipitation rates due to changes in atmospheric dynamics, decreased evaporation rates resulting from temperature depression and summer insolation changes, or some combination of the two remains uncertain. The factors contributing to these large-scale changes in hydroclimate are critical to resolve, given that this region is poised to undergo future anthropogenic-forced climate changes with large uncertainties in model simulations for the 21st century. Furthermore, there are ambiguous constraints on the magnitude and even the sign of changes in key hydroclimate variables between the Last Glacial Maximum and the present day in both proxy reconstructions and climate model analyses of the region. Here we report thermodynamically derived estimates of changes in temperature, precipitation, and evaporation rates, as well as the isotopic composition of lake water, using clumped isotope data from an ancient lake in the northwestern Great Basin, Lake Surprise (California). Compared to modern climate, mean annual air temperature at Lake Surprise was 4.7 °C lower during the Last Glacial Maximum, with decreased evaporation rates and similar precipitation rates to modern. During the mid-deglacial period, the growth of Lake Surprise implied that the lake hydrologic budget briefly departed from steady state. Our reconstructions indicate that this growth took place rapidly, while the subsequent lake regression took place over several thousand years. Using models for precipitation and evaporation constrained from clumped isotope results, we determine that the disappearance of Lake Surprise coincided with a moderate increase in lake temperature, along with increasing evaporation rates outpacing increasing precipitation rates. Concomitant analysis of proxy data and climate model simulations for the Last Glacial Maximum are used to provide a robust means to understand past climate change, and by extension, predict how current hydroclimates may respond to expected future climate forcings. We suggest that an expansion of this analysis to more basins across a larger spatial scale could provide valuable insight into proposed climate forcings, and aid in climate model process depiction. Ultimately, our analysis highlights the importance of temperature-driven evaporation as a mechanism for lake growth and retreat in this region.

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 A three-dimensional climate—ice-sheet model applied to the Last Glacial Maximum

1997 ◽  
Vol 25 ◽  
pp. 333-339 ◽  
Author(s):  
Philippe Huybrechts ◽  
Stephen T’siobbel
Keyword(s):  
Last Glacial Maximum ◽  
Northern Hemisphere ◽  
Climate Model ◽  
Three Dimensional ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

A quasi-three-dimensional (3-D) climate model (Sellers, 1983) was used to simulate the climate of the Last Glacial Maximum (LGM) in order to provide climatic input for the modelling of the Northern Hemisphere ice sheets. The climate model is basically a coarse-gridded general circulation (GCM) with simplified dynamics, and was subject to appropriate boundary conditions for ice-sheet elevation, atmospheric CO2concentration and orbital parameters. When compared with the present-daysimulation, the simulated climate at the Last Glacial Maximum is characterized by a global annual cooling of 3.5°C and a reduction in global annualprecipitation of 7.5%, which agrees well with results from other, more complex GCMs. Also the patterns of temperature change compare fairly with mostother GCM results, except for a smaller cooling over the North Atlantic and the larger cooling predicted for the summer rather than for the winter over Eurasia.The climate model is able to simulate changes in Northern Hemisphere tropospheric circulation, yielding enhanced westerlies in the vicinity of the Laurentide and Eurasian ice sheets. However, the simulated precipitation patterns are less convincing, and show a distinct mean precipitation increase over the Laurentide ice sheet. Nevertheless, when using the mean-monthly fields of LGM minus present-day anomalies of temperature and precipitation rate to drive a three-dimensional thermomechanical ice-sheet model, it was demonstrated that within realistic bounds of the ice-flow and mass-balance parameters, veryreasonable reconstructions of the Last Glacial Maximum ice sheets could be obtained.

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.

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 Global peatlands under future climate – seamless model projections from the Last Glacial Maximum

2021 ◽  
Author(s):  
Jurek Müller ◽  
Fortunat Joos
Keyword(s):  
Last Glacial Maximum ◽  
Climate Model ◽  
Coupled Model ◽  
Glacial Maximum ◽  
Dynamic Global Vegetation Model ◽  
Last Glacial ◽  
The Future ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Peatlands are diverse wetland ecosystems distributed mostly over the northern latitudes and tropics. Globally they store a large portion of the global soil organic carbon and provide important ecosystem services. The future of these systems under continued anthropogenic warming and direct human disturbance has potentially large impacts on atmospheric CO2 and climate. We performed global long term projections of peatland area and carbon over the next 5000 years using a dynamic global vegetation model forced with climate anomalies from ten models of the Coupled Model Intercomparison Project (CMIP6) and three scenarios. These projections are continued from a transient simulation from the Last Glacial Maximum to the present to account for the full transient history. Our results suggest short to long term net losses of global peatland area and carbon, with higher losses under higher emission scenarios. Large parts of today's active northern peatlands are at risk. Conditions for peatlands in the tropics and, in case of mitigation, eastern Asia and western north America improve. Factorial simulations reveal committed historical changes and future rising temperature as the main driver of future peatland loss and increasing precipitations as driver for regional peatland expansion. Additional simulations forced with two CMIP6 scenarios extended transiently beyond 2100, show qualitatively similar results to the standard scenarios, but highlight the importance of extended future scenarios for long term carbon cycle projections. The spread between simulations forced with different climate model anomalies suggests a large uncertainty in projected peatland variables due to uncertain climate forcing. Our study highlights the importance of quantifying the future peatland feedback to the climate system and its inclusion into future earth system model projections.

scholarly journals A three-dimensional climate—ice-sheet model applied to the Last Glacial Maximum

1997 ◽  
Vol 25 ◽  
pp. 333-339 ◽  
Author(s):  
Philippe Huybrechts ◽  
Stephen T’siobbel
Keyword(s):  
Last Glacial Maximum ◽  
Northern Hemisphere ◽  
Climate Model ◽  
Three Dimensional ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

A quasi-three-dimensional (3-D) climate model (Sellers, 1983) was used to simulate the climate of the Last Glacial Maximum (LGM) in order to provide climatic input for the modelling of the Northern Hemisphere ice sheets. The climate model is basically a coarse-gridded general circulation (GCM) with simplified dynamics, and was subject to appropriate boundary conditions for ice-sheet elevation, atmospheric CO2 concentration and orbital parameters. When compared with the present-daysimulation, the simulated climate at the Last Glacial Maximum is characterized by a global annual cooling of 3.5°C and a reduction in global annualprecipitation of 7.5%, which agrees well with results from other, more complex GCMs. Also the patterns of temperature change compare fairly with mostother GCM results, except for a smaller cooling over the North Atlantic and the larger cooling predicted for the summer rather than for the winter over Eurasia.The climate model is able to simulate changes in Northern Hemisphere tropospheric circulation, yielding enhanced westerlies in the vicinity of the Laurentide and Eurasian ice sheets. However, the simulated precipitation patterns are less convincing, and show a distinct mean precipitation increase over the Laurentide ice sheet. Nevertheless, when using the mean-monthly fields of LGM minus present-day anomalies of temperature and precipitation rate to drive a three-dimensional thermomechanical ice-sheet model, it was demonstrated that within realistic bounds of the ice-flow and mass-balance parameters, veryreasonable reconstructions of the Last Glacial Maximum ice sheets could be obtained.

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