scholarly journals The Partitioning of Meridional Heat Transport from the Last Glacial Maximum to CO2 Quadrupling in Coupled Climate Models

2020 ◽  
Vol 33 (10) ◽  
pp. 4141-4165 ◽  
Author(s):  
Aaron Donohoe ◽  
Kyle C. Armour ◽  
Gerard H. Roe ◽  
David S. Battisti ◽  
Lily Hahn
Keyword(s):  
Heat Transport ◽  
Last Glacial Maximum ◽  
Climate Models ◽  
Energy Transport ◽  
Glacial Maximum ◽  
Meridional Heat Transport ◽  
Last Glacial ◽  
Coupled Climate Models ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractMeridional heat transport (MHT) is analyzed in ensembles of coupled climate models simulating climate states ranging from the Last Glacial Maximum (LGM) to quadrupled CO2. MHT is partitioned here into atmospheric (AHT) and implied oceanic (OHT) heat transports. In turn, AHT is partitioned into dry and moist energy transport by the meridional overturning circulation (MOC), transient eddy energy transport (TE), and stationary eddy energy transport (SE) using only monthly averaged model output that is typically archived. In all climate models examined, the maximum total MHT (AHT + OHT) is nearly climate-state invariant, except for a modest (4%, 0.3 PW) enhancement of MHT in the Northern Hemisphere (NH) during the LGM. However, the partitioning of MHT depends markedly on the climate state, and the changes in partitioning differ considerably among different climate models. In response to CO2 quadrupling, poleward implied OHT decreases, while AHT increases by a nearly compensating amount. The increase in annual-mean AHT is a smooth function of latitude but is due to a spatially inhomogeneous blend of changes in SE and TE that vary by season. During the LGM, the increase in wintertime SE transport in the NH midlatitudes exceeds the decrease in TE resulting in enhanced total AHT. Total AHT changes in the Southern Hemisphere (SH) are not significant. These results suggest that the net top-of-atmosphere radiative constraints on total MHT are relatively invariant to climate forcing due to nearly compensating changes in absorbed solar radiation and outgoing longwave radiation. However, the partitioning of MHT depends on detailed regional and seasonal factors.

Atmospheric equilibrium, instability and energy transport at the last glacial maximum

1996 ◽  
Vol 12 (7) ◽  
pp. 497-511 ◽  
Author(s):  
Nicholas M. J. Hall ◽  
Buwen Dong ◽  
Paul J. Valdes
Keyword(s):  
Last Glacial Maximum ◽  
Energy Transport ◽  
Glacial Maximum ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

scholarly journals A new global reconstruction of temperature changes at the Last Glacial Maximum

2013 ◽  
Vol 9 (1) ◽  
pp. 367-376 ◽  
Author(s):  
J. D. Annan ◽  
J. C. Hargreaves
Keyword(s):  
Last Glacial Maximum ◽  
Climate Models ◽  
State Of The Art ◽  
Glacial Maximum ◽  
Proxy Data ◽  
Temperature Changes ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
Global Mean ◽  
The Last Glacial

Abstract. Some recent compilations of proxy data both on land and ocean (MARGO Project Members, 2009; Bartlein et al., 2011; Shakun et al., 2012), have provided a new opportunity for an improved assessment of the overall climatic state of the Last Glacial Maximum. In this paper, we combine these proxy data with the ensemble of structurally diverse state of the art climate models which participated in the PMIP2 project (Braconnot et al., 2007) to generate a spatially complete reconstruction of surface air (and sea surface) temperatures. We test a variety of approaches, and show that multiple linear regression performs well for this application. Our reconstruction is significantly different to and more accurate than previous approaches and we obtain an estimated global mean cooling of 4.0 ± 0.8 °C (95% CI).

Influence of ocean heat transport on the climate of the Last Glacial Maximum

Nature ◽  
1997 ◽  
Vol 385 (6618) ◽  
pp. 695-699 ◽  
Author(s):  
Robert S. Webb ◽  
David H. Rind ◽  
Scott J. Lehman ◽  
Richard J. Healy ◽  
Daniel Sigman
Keyword(s):  
Heat Transport ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Ocean Heat Transport ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

scholarly journals The Last Glacial Maximum in the central North Island, New Zealand: palaeoclimate inferences from glacier modelling

2016 ◽  
Vol 12 (4) ◽  
pp. 943-960 ◽  
Author(s):  
Shaun R. Eaves ◽  
Andrew N. Mackintosh ◽  
Brian M. Anderson ◽  
Alice M. Doughty ◽  
Dougal B. Townsend ◽  
...  
Keyword(s):  
New Zealand ◽  
Last Glacial Maximum ◽  
Climate Models ◽  
Glacial Maximum ◽  
Local Climate ◽  
Last Glacial ◽  
Mountain Glaciers ◽  
Spatial Coverage ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Quantitative palaeoclimate reconstructions provide data for evaluating the mechanisms of past, natural climate variability. Geometries of former mountain glaciers, constrained by moraine mapping, afford the opportunity to reconstruct palaeoclimate, due to the close relationship between ice extent and local climate. In this study, we present results from a series of experiments using a 2-D coupled energy balance–ice flow model that investigate the palaeoclimate significance of Last Glacial Maximum moraines within nine catchments in the central North Island, New Zealand. We find that the former ice limits can be simulated when present-day temperatures are reduced by between 4 and 7 °C, if precipitation remains unchanged from present. The spread in the results between the nine catchments is likely to represent the combination of chronological and model uncertainties. The majority of catchments targeted require temperature decreases of 5.1 to 6.3 °C to simulate the former glaciers, which represents our best estimate of the temperature anomaly in the central North Island, New Zealand, during the Last Glacial Maximum. A decrease in precipitation of up to 25 % from present, as suggested by proxy evidence and climate models, increases the magnitude of the required temperature changes by up to 0.8 °C. Glacier model experiments using reconstructed topographies that exclude the volume of post-glacial ( <  15 ka) volcanism generally increased the magnitude of cooling required to simulate the former ice limits by up to 0.5 °C. Our palaeotemperature estimates expand the spatial coverage of proxy-based quantitative palaeoclimate reconstructions in New Zealand. Our results are also consistent with independent, proximal temperature reconstructions from fossil groundwater and pollen assemblages, as well as similar glacier modelling reconstructions from the central Southern Alps, which suggest air temperatures were ca. 6 °C lower than present across New Zealand during the Last Glacial Maximum.

scholarly journals Results of PMIP2 coupled simulations of the Mid-Holocene and Last Glacial Maximum – Part 1: experiments and large-scale features

2007 ◽  
Vol 3 (2) ◽  
pp. 261-277 ◽  
Author(s):  
P. Braconnot ◽  
B. Otto-Bliesner ◽  
S. Harrison ◽  
S. Joussaume ◽  
J.-Y. Peterchmitt ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Large Scale ◽  
Climate Models ◽  
Glacial Maximum ◽  
Second Phase ◽  
Atmospheric Models ◽  
Last Glacial ◽  
Intercomparison Project ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. A set of coupled ocean-atmosphere simulations using state of the art climate models is now available for the Last Glacial Maximum and the Mid-Holocene through the second phase of the Paleoclimate Modeling Intercomparison Project (PMIP2). This study presents the large-scale features of the simulated climates and compares the new model results to those of the atmospheric models from the first phase of the PMIP, for which sea surface temperature was prescribed or computed using simple slab ocean formulations. We consider the large-scale features of the climate change, pointing out some of the major differences between the different sets of experiments. We show in particular that systematic differences between PMIP1 and PMIP2 simulations are due to the interactive ocean, such as the amplification of the African monsoon at the Mid-Holocene or the change in precipitation in mid-latitudes at the LGM. Also the PMIP2 simulations are in general in better agreement with data than PMIP1 simulations.

scholarly journals The Last Glacial Maximum in central North Island, New Zealand: palaeoclimate inferences from glacier modelling

2016 ◽  
Author(s):  
Shaun R. Eaves ◽  
Andrew N. Mackintosh ◽  
Brian A. Anderson ◽  
Alice M. Doughty ◽  
Dougal B. Townsend ◽  
...  
Keyword(s):  
New Zealand ◽  
Last Glacial Maximum ◽  
Climate Models ◽  
Glacial Maximum ◽  
Local Climate ◽  
Last Glacial ◽  
Mountain Glaciers ◽  
Spatial Coverage ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Quantitative palaeoclimate reconstructions provide data for evaluating the mechanisms of past, natural climate variability. Geometries of former mountain glaciers constrained by moraine mapping afford the opportunity to reconstruct palaeoclimate, due to the close relationship between ice extent and local climate. In this study, we present results from a series of experiments using a 2D coupled energy-balance/ice-flow model that investigate the palaeoclimate significance of Last Glacial Maximum moraines within nine catchments in central North Island, New Zealand. We find that the former ice limits can be simulated when present day temperatures are reduced by between 4 °C and 7 °C, when precipitation remains unchanged from present. The spread in the results between the nine catchments is likely to represent the combination of chronological and model uncertainties. The temperature decrease required to simulate the former glaciers falls in the range of 5.1 °C and 6.3 °C for the majority of catchments targeted, which represents our best estimate of the peak temperature anomaly in central North Island, New Zealand during the Last Glacial Maximum. A decrease in precipitation, as suggested by proxy evidence and climate models, of up to 25 % from present, increases the magnitude of the required temperature changes by up to 0.8 °C. Glacier model experiments using reconstructed topographies that exclude the volume of post-glacial (<15 ka) volcanism, generally increased the magnitude of cooling required to simulate the former ice limits by up to 0.5 °C. Our palaeotemperature estimates expand the spatial coverage of proxy-based quantitative palaeoclimate reconstructions in New Zealand, and are consistent with independent, proximal temperature reconstructions from fossil pollen assemblages, as well as similar glacier modelling reconstructions from central Southern Alps.

scholarly journals The Last Glacial Maximum in the central North Island, New Zealand: Palaeoclimate inferences from glacier modelling

2021 ◽  
Author(s):  
Shaun Eaves ◽  
AN Mackintosh ◽  
Brian Anderson ◽  
AM Doughty ◽  
DB Townsend ◽  
...  
Keyword(s):  
New Zealand ◽  
Last Glacial Maximum ◽  
Climate Models ◽  
Glacial Maximum ◽  
Local Climate ◽  
Last Glacial ◽  
Mountain Glaciers ◽  
Spatial Coverage ◽  
The Last Glacial Maximum ◽  
The Last Glacial

© Author(s) 2016. Quantitative palaeoclimate reconstructions provide data for evaluating the mechanisms of past, natural climate variability. Geometries of former mountain glaciers, constrained by moraine mapping, afford the opportunity to reconstruct palaeoclimate, due to the close relationship between ice extent and local climate. In this study, we present results from a series of experiments using a 2-D coupled energy balance-ice flow model that investigate the palaeoclimate significance of Last Glacial Maximum moraines within nine catchments in the central North Island, New Zealand. We find that the former ice limits can be simulated when present-day temperatures are reduced by between 4 and 7°C, if precipitation remains unchanged from present. The spread in the results between the nine catchments is likely to represent the combination of chronological and model uncertainties. The majority of catchments targeted require temperature decreases of 5.1 to 6.3°C to simulate the former glaciers, which represents our best estimate of the temperature anomaly in the central North Island, New Zealand, during the Last Glacial Maximum. A decrease in precipitation of up to 25% from present, as suggested by proxy evidence and climate models, increases the magnitude of the required temperature changes by up to 0.8°C. Glacier model experiments using reconstructed topographies that exclude the volume of post-glacial (< 15 ka) volcanism generally increased the magnitude of cooling required to simulate the former ice limits by up to 0.5°C. Our palaeotemperature estimates expand the spatial coverage of proxy-based quantitative palaeoclimate reconstructions in New Zealand. Our results are also consistent with independent, proximal temperature reconstructions from fossil groundwater and pollen assemblages, as well as similar glacier modelling reconstructions from the central Southern Alps, which suggest air temperatures were ca. 6°C lower than present across New Zealand during the Last Glacial Maximum.

scholarly journals Optimal Geometric Characterization of Forced Zonal Mean Tropical Precipitation Changes.

2021 ◽  
Author(s):  
Aaron Donohoe ◽  
Alyssa R Atwood ◽  
David S Battisti
Keyword(s):  
Last Glacial Maximum ◽  
Climate Models ◽  
Global Climate ◽  
Glacial Maximum ◽  
Global Climate Models ◽  
Last Glacial ◽  
Tropical Precipitation ◽  
Precipitation Changes ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract The zonal and annual mean tropical precipitation response to paleoclimate and anthropogenic forcing scenarios ranging from the Last Glacial Maximum (LGM), CO2 quadrupling (4XCO2 ), mid-Holocene, North Atlantic freshwater hosing and volcanic forcing is analyzed in an ensemble of global climate models. Zonally averaged tropical precipitation changes are characterized in terms of three geometric manipulations of the climatological precipitation (hereafter, modes): meridional shifts, intensifications, and meridional contractions. We employ an optimization procedure that quantifies the magnitude and robustness (across different models) of changes in each mode in response to each forcing type. Additionally, the fraction of precipitation changes that are explained by the modes (in isolation and combined) is quantified. Shifts are generally less than 1º latitude in magnitude and explain a small fraction (<10%) of tropical precipitation changes. Contractions and intensifications are strongly anti-correlated across all simulations with a robust intensification and contraction of precipitation under global warming and a robust reduction and expansion under global cooling during the Last Glacial Maximum. The near constant scaling between contractions and intensifications across all simulations is used to define a joint contraction/intensification (CI) mode of tropical precipitation. The CI mode explains nearly 50% of the precipitation change under 4XCO2 and LGM forcing by optimizing a single parameter. These results suggest the shifting mode that has been extensively used to interpret paleo-rainfall reconstructions is of limited use for characterizing forced zonal mean precipitation changes and advocates for a reinterpretation of past precipitation changes to account for the CI mode

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