scholarly journals Climate simulations and pollen data reveal the distribution and connectivity of temperate tree populations in eastern Asia during the Last Glacial Maximum

2020 ◽  
Author(s):  
Suzanne Alice Ghislaine Leroy ◽  
Klaus Arpe ◽  
Uwe Mikolajewicz ◽  
Jing Wu
Keyword(s):  
Climate Model ◽  
Deciduous Tree ◽  
Deciduous Trees ◽  
Eastern Asia ◽  
Pollen Data ◽  
Climate Simulations ◽  
Temperate Deciduous ◽  
Climate Model Simulations ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Publications on temperate deciduous tree refugia in Europe are abundant, but little is known about the patterns of temperate tree refugia in eastern Asia, an area where biodiversity survived Quaternary glaciations and which has the world's most diverse temperate flora. Our goal is to compare climate model simulations with pollen data in order to establish the location of glacial refugia during the Last Glacial Maximum (LGM) period. Limits in which temperate deciduous trees can survive are taken from the literature. The model outputs are first tested for the present by comparing climate models with published modern pollen data. As this method turned out to be satisfactory for the present, the same approach was used for the LGM, Climate model simulations (ECHAM5 T106), statistically further down-scaled, are used to infer the temperate deciduous trees distribution during the LGM. These were compared with available fossil temperate tree pollen occurrences. The impact of the LGM on the eastern Asia climate was much weaker than on the European climate. The area of possible tree growth shifts only by about 2° to the south between the present and the LGM. This contributes to explain the greater biodiversity of forests in eastern Asia compared to Europe. Climate simulations and the available, although fractional, fossil pollen data agree. Therefore climate estimations can safely be used to fill areas without pollen data by mapping potential refugia distributions. The results show two important areas with population connectivity: the Yellow Sea emerged shelf and the southern Himalayas. These two areas were suitable for temperate deciduous tree growth, providing corridors for population migration and connectivity (i.e. less population fragmentation) in glacial and in interglacial periods. Many tree populations live in interglacial refugia; not glacial ones. The fact that the model simulation for the LGM fits so well with observed pollen distribution is another indication that the used model is good to simulate also the LGM period.

scholarly journals Climate simulations and pollen data reveal the distribution and connectivity of temperate tree populations in eastern Asia during the Last Glacial Maximum

2020 ◽  
Vol 16 (6) ◽  
pp. 2039-2054
Author(s):  
Suzanne Alice Ghislaine Leroy ◽  
Klaus Arpe ◽  
Uwe Mikolajewicz ◽  
Jing Wu
Keyword(s):  
Climate Model ◽  
Deciduous Tree ◽  
Eastern Asia ◽  
Pollen Data ◽  
Model Simulations ◽  
Climate Simulations ◽  
Temperate Deciduous ◽  
Climate Model Simulations ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Publications on temperate deciduous tree refugia in Europe are abundant, but little is known about the patterns of temperate tree refugia in eastern Asia, an area where biodiversity survived Quaternary glaciations and which has the world's most diverse temperate flora. Our goal is to compare climate model simulations with pollen data in order to establish the location of glacial refugia during the Last Glacial Maximum (LGM). Limits in which temperate deciduous trees can survive are taken from the literature. The model outputs are first tested for the present by comparing climate models with published modern pollen data. As this method turned out to be satisfactory for the present, the same approach was used for the LGM. Climate model simulations (ECHAM5 T106), statistically further downscaled, are used to infer the temperate deciduous tree distribution during the LGM. These were compared with available fossil temperate tree pollen occurrences. The impact of the LGM on the eastern Asian climate was much weaker than on the European climate. The area of possible tree growth shifts only by about 2∘ to the south between the present and the LGM. This contributes to explaining the greater biodiversity of forests in eastern Asia compared to Europe. Climate simulations and the available, although fractional, fossil pollen data agree. Therefore, climate estimations can safely be used to fill areas without pollen data by mapping potential refugia distributions. The results show two important areas with population connectivity: the Yellow Sea emerged shelf and the southern Himalayas. These two areas were suitable for temperate deciduous tree growth, providing corridors for population migration and connectivity (i.e. less population fragmentation) in glacial periods. Many tree populations live in interglacial refugia, not glacial ones. The fact that the model simulation for the LGM fits so well with observed pollen distribution is another indication that the model used is good enough to also simulate the LGM period.

Poleward shift in the Southern Ocean westerlies synchronous with the deglacial rise in atmospheric CO2

2020 ◽  
Author(s):  
William Gray ◽  
Robert Wills ◽  
Elisabeth Michel ◽  
Masa Kageyama
Keyword(s):  
Southern Ocean ◽  
Feedback Loop ◽  
Climate Model ◽  
Last Deglaciation ◽  
Westerly Winds ◽  
Poleward Shift ◽  
The Last Deglaciation ◽  
Climate Model Simulations ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>The Southern Ocean westerly winds are hypothesised to play a key role in regulating atmospheric CO<sub>2</sub> over glacial-interglacial cycles; constraints on the paleo-latitude of the westerly winds have, however, remained allusive.  Here we use changes in the spatial pattern of planktic foraminiferal ∂<sup>18</sup>O to track changes in the latitude of the Southern Ocean polar and subtropical fronts over the last deglaciation, which are closely tied to the position of the westerly winds. We find a ~5° equator-ward shift in the position of the fronts (and thus westerlies) during the last glacial maximum relative to their Holocene position. Our reconstruction shows the poleward shift in the westerlies over deglaciation closely mirrors the sub-millennial scale variability seen in the rise in atmospheric CO<sub>2</sub>. We propose that changes in the position of the westerly winds modulate CO<sub>2</sub> via changes in the extent of Southern Ocean sea ice and circulation of the abyssal ocean. Using climate model simulations, we explore the possibility of a feedback loop by which these CO<sub>2</sub>/climatic changes may lead to further changes in the position of the westerly winds.</p>

scholarly journals A comparison of climate simulations for the last glacial maximum with three different versions of the ECHAM model and implications for summer-green tree refugia

2011 ◽  
Vol 7 (1) ◽  
pp. 91-114 ◽  
Author(s):  
K. Arpe ◽  
S. A. G. Leroy ◽  
U. Mikolajewicz
Keyword(s):  
Last Glacial Maximum ◽  
Tree Growth ◽  
Western Europe ◽  
Glacial Maximum ◽  
The Other ◽  
Last Glacial ◽  
Climate Simulations ◽  
Southward Shift ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Model simulations of the last glacial maximum (21 ± 2 ka) with the ECHAM3 T42 atmosphere-only, ECHAM5-MPIOM T31 atmosphere-ocean coupled and ECHAM5 T106 atmosphere-only models are compared. The topography, land-sea mask and glacier distribution for the ECHAM5 simulations were taken from the Paleoclimate Modelling Intercomparison Project Phase II (PMIP2) data set while for ECHAM3 they were taken from PMIP1. The ECHAM5-MPIOM T31 model produced its own sea surface temperatures (SST) while the ECHAM5 T106 simulations were forced at the boundaries by this coupled model SSTs corrected from their present-day biases and the ECHAM3 T42 model was forced with prescribed SSTs provided by Climate/Long-Range Investigation, Mapping, and Prediction project (CLIMAP). The SSTs in the ECHAM5-MPIOM simulation for the last glacial maximum (LGM) were much warmer in the northern Atlantic than those suggested by CLIMAP or Overview of Glacial Atlantic Ocean Mapping (GLAMAP) while the SSTs were cooler everywhere else. This had a clear effect on the temperatures over Europe, warmer for winters in western Europe and cooler for eastern Europe than the simulation with CLIMAP SSTs. Considerable differences in the general circulation patterns were found in the different simulations. A ridge over western Europe for the present climate during winter in the 500 hPa height field remains in both ECHAM5 simulations for the LGM, more so in the T106 version, while the ECHAM3 CLIMAP-SST simulation provided a trough which is consistent with cooler temperatures over western Europe. The zonal wind between 30° W and 10° E shows a southward shift of the polar and subtropical jets in the simulations for the LGM, least obvious in the ECHAM5 T31 one, and an extremely strong polar jet for the ECHAM3 CLIMAP-SST run. The latter can probably be assigned to the much stronger north-south gradient in the CLIMAP SSTs. The southward shift of the polar jet during the LGM is supported by palaeo-data. Cyclone tracks in winter represented by high precipitation are characterised over Europe for the present by a main branch from the British Isles to Norway and a secondary branch towards the Mediterranean Sea, observed and simulated. For the LGM the different models show very different solutions: the ECHAM3 CLIMAP-SST simulation shows just one track going eastward from the British Isles into central Europe, while the ECHAM5 T106 simulation still has two branches but during the LGM the main one goes to the Mediterranean Sea, with enhanced precipitation in the Levant. This agrees with an observed high stand of the Dead Sea during the LGM. For summer the ECHAM5 T106 simulation provides much more precipitation for the present over Europe than the other simulations, thus agreeing with estimates by the Global Precipitation Climatology Project (GPCP). Also during the LGM this model makes Europe less arid than the other simulations. In many respects the ECHAM5 T106 simulation for the present is more realistic than the ECHAM5 T31 coupled simulation and the older ECHAM3 T42 simulation, when comparing them with the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis or the GPCP precipitation data. For validating the model data for the LGM, pollen, wood and charcoal analyses were compared with possible summer-green tree growth from model estimates using summer precipitation, minimum winter temperatures and growing degree days (above 5 °C). The ECHAM5 T106 simulation suggests for more sites with findings of palaeo-data, likely tree growth during the LGM than the other simulations, especially over western Europe. The clear message especially from the ECHAM5 T106 simulation is that warm-loving summer-green trees could have survived mainly in Spain but also in Greece in agreement with findings of pollen or charcoal. Southern Italy is also suggested but this could not be validated because of absence of palaeo-data. Previous climate simulations of the LGM have suggested less cold and more humid climate than that reconstructed from pollen findings. Our model results do agree more or less with those of other models but we do not find a contradiction with palaeo-data because we use the pollen data directly without an intermediate reconstruction of temperatures and precipitation from the pollen spectra.

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.

scholarly journals A pragmatic approach for the downscaling and bias correction of regional climate simulations – evaluation in hydrological modeling

2011 ◽  
Vol 4 (1) ◽  
pp. 45-63 ◽  
Author(s):  
T. Marke ◽  
W. Mauser ◽  
A. Pfeiffer ◽  
G. Zängl
Keyword(s):  
Hydrological Modeling ◽  
Hydrological Model ◽  
Climate Model ◽  
Regional Climate ◽  
Model Performance ◽  
Reanalysis Data ◽  
Historical Period ◽  
Climate Simulations ◽  
Meteorological Observations ◽  
Climate Model Simulations

Abstract. The present study investigates a statistical approach for the downscaling of climate simulations focusing on those meteorological parameters most commonly required as input for climate change impact models (temperature, precipitation, air humidity and wind speed), including the option to correct biases in the climate model simulations. The approach is evaluated by the utilization of a hydrometeorological model chain consisting of (i) the regional climate model MM5 (driven by reanalysis data at the boundaries of the model domain), (ii) the downscaling and model interface SCALMET, and (iii) the hydrological model PROMET. The results of four hydrological model runs are compared to discharge recordings at the gauge of the Upper Danube Watershed (Central Europe) for the historical period of 1972–2000 on a daily time basis. The comparison reveals that the presented approaches allow for a more accurate simulation of discharge for the catchment of the Upper Danube Watershed and the considered gauge at the outlet in Achleiten. The correction for subgrid-scale variability is shown to reduce biases in simulated discharge compared to the utilization of bilinear interpolation. Further enhancements in model performance could be achieved by a correction of biases in the RCM data within the downscaling process. Although the presented downscaling approach strongly improves the performance of the hydrological model, deviations from the observed discharge conditions persist that are not found when driving the hydrological model with spatially distributed meteorological observations.

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