Investigation of the response of water isotope records to the changes in orbital forcing with the isotope-enabled AGCM MIROC5-iso

2020 ◽  
Author(s):  
Kanon Kino ◽  
Atsushi Okazaki ◽  
Alexandre Cauquoin ◽  
Kei Yosnimura
Keyword(s):  
General Circulation ◽  
Ice Cores ◽  
General Circulation Models ◽  
Orbital Forcing ◽  
Stable Water Isotopes ◽  
Orbital Parameters ◽  
Ice Coverage ◽  
Milankovitch Theory ◽  
Simulation Results ◽  
Water Isotope

<p>It has been well demonstrated that the variations of orbital parameters, known as Milankovitch theory, are one of the most important drivers of the Earth’s climate system. However, the way how the changes in orbital forcing imprint the glacial-interglacial cycles recorded in paleo-proxies, such as stable water isotopes in ice cores and speleothems, is still unclear. One way to progress in this question is to make direct comparisons of isotopic data with simulation results from isotope-enabled General Circulation Models (GCMs). We use here such a model, the Japanese atmospheric GCM MIROC5-iso[1], to perform simulations under different idealized paleoclimate conditions. For that, corresponding orbital parameters and greenhouse gases concentrations are set. Prescribed sea surface temperature and sea ice coverage boundary conditions from the fully coupled atmosphere-ocean GCM MIROC (MIROC-AOGCM) experiments are used, after an adaptation to the MIROC5-iso grid. Because earlier version of MIROC-AOGCM has been widely used for paleoclimate modeling purposes, the climatological mean states of MIROC5-iso under preindustrial conditions are evaluated against simulation results from different versions of MIROC-AOGCM (MIROC4m, which is a slightly updated version of MIROC3.2(med), and MIROC5 [2]). In addition, several interglacial periods and idealized paleoclimate experiments will be investigated and implications for the interpretation of water isotope response to the changes in orbital forcing will be discussed.</p><p>[1] Okazaki and Yoshimura, J. Geophys. Res. Atmos, <strong>124</strong>, 8972–8993, 2019.</p><p><span>[</span>2<span>]</span> Watanabe et al., J. Climate, <strong>23</strong>, 6312–6335, 2010.</p>

High-resolution isotopic simulations from ECHAM6-wiso nudged with ERA5 reanalyses: new products for isotopic model-data comparisons

2020 ◽  
Author(s):  
Alexandre Cauquoin ◽  
Martin Werner
Keyword(s):  
General Circulation ◽  
Ice Cores ◽  
General Circulation Models ◽  
Global Network ◽  
Climate Data ◽  
Isotopic Data ◽  
Surrounding Water ◽  
Weather Forecasts ◽  
The Impact ◽  
Water Isotope

<p>For several decades, the comparison of climate data with results from water isotope-enabled Atmosphere General Circulation Models (AGCMs) significantly helped to a better understanding of the processes ruling the water cycle, which is one of the main drivers of the climate variability. For the modern period, the use of AGCMs nudged with weather forecasts reanalyses is a powerful way to obtain model outputs under the same weather conditions than at the sampling time of the observations.</p><p>Here we present new isotopic simulations results from ECHAM6-wiso [1] nudged with the last reanalyses dataset from the European Centre for Medium-Range Weather Forecasts (ECMWF), ERA5 [2], at different spatial resolutions over the period 1979-2018. Model results are evaluated against isotopic data compilations, including GNIP (Global Network of Isotopes in Precipitation [3]), speleothems [4], ice cores datasets and water vapor measurements. To quantify the impact of these reanalyses on our simulations, we also performed nudged simulations with the previous model version ECHAM5-wiso [5] by using ERA5 data and its predecessor ERA-Interim [6].</p><p>These new simulation products could be a useful contribution to the isotopic data community for the interpretation of their water isotope records and for the exploration of the mechanisms controlling the variability of the surrounding water isotopic composition.</p><p> </p><p>[1] Cauquoin et al., Clim. Past, <strong>15</strong>, 1913–1937, https://doi.org/10.5194/cp-15-1913-2019, 2019.</p><p>[2] Copernicus Climate Change Service (C3S), 2017.</p><p>[3] IAEA, the GNIP Database, available at: https://nucleus.iaea.org/wiser.</p><p>[4] Comas-Bru et al., Clim. Past, <strong>15</strong>, 1557–1579, https://doi.org/10.5194/cp-15-1557-2019, 2019.</p><p>[5] Werner et al., Geosci. Model Dev., <strong>9</strong>, 647–670, https://doi.org/10.5194/gmd-9-647-2016, 2016.</p><p>[6] Dee et al., Q. J. R. Meteorol. Soc., <strong>137</strong>, 553–597, https://doi.org/10.1002/qj.828, 2011.</p>

Sensitivity of simulated oxygen isotopes in ice cores and speleothems to Last Glacial Maximum surface conditions

2021 ◽  
Author(s):  
André Paul ◽  
Alexandre Cauquoin ◽  
Stefan Mulitza ◽  
Thejna Tharammal ◽  
Martin Werner
Keyword(s):  
Last Glacial Maximum ◽  
General Circulation ◽  
Ice Cores ◽  
General Circulation Models ◽  
Glacial Maximum ◽  
Sea Surface ◽  
Surface Conditions ◽  
Last Glacial ◽  
The Impact ◽  
Mean Square Errors

<p>In simulations of the climate during the Last Glacial Maximum (LGM), we employ two different isotope-enabled atmospheric general circulation models (NCAR iCAM3 and MPI ECHAM6-wiso) and use simulated (by coupled climate models) as well as reconstructed (from a new global climatology of the ocean surface duing the LGM, GLOMAP) surface conditions.</p><p>The resulting atmospheric fields reflect the more pronounced structure and gradients in the reconstructions, for example, the precipitation is more depleted in oxygen-18 in the high latitudes and more enriched in low latitudes, especially in the tropical convective regions over the maritime continent in the equatorial Pacific and Indian Oceans and over the equatorial Atlantic Ocean. Furthermore, at the sites of ice cores and speleothems, the model-data fit improves in terms of the coefficients of determination and root-mean square errors.</p><p>In additional sensitivity experiments, we also use the climatologies by Annan and Hargreaves (2013) and Tierney et al. (2020) and consider the impact of changes in reconstructed sea-ice extent and the global-mean sea-surface temperature.</p><p>Our findings imply that the correct simulation or reconstruction of patterns and gradients in sea-surface conditions are crucial for a successful comparison to oxygen-isotope data from ice cores and speleothems.</p>

scholarly journals Applying an isotope-enabled regional climate model over the Greenland ice sheet: effect of spatial resolution on model bias

2021 ◽  
Vol 17 (4) ◽  
pp. 1685-1699
Author(s):  
Marcus Breil ◽  
Emanuel Christner ◽  
Alexandre Cauquoin ◽  
Martin Werner ◽  
Melanie Karremann ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
General Circulation ◽  
Climate Model ◽  
Regional Climate ◽  
Circulation Model ◽  
Ice Cores ◽  
Arctic Region ◽  
The Arctic ◽  
Simulation Results ◽  
The Arctic Region

Abstract. In order to investigate the impact of spatial resolution on the discrepancy between simulated δ18O and observed δ18O in Greenland ice cores, regional climate simulations are performed with the isotope-enabled regional climate model (RCM) COSMO_iso. For this purpose, isotope-enabled general circulation model (GCM) simulations with the ECHAM5-wiso general circulation model (GCM) under present-day conditions and the MPI-ESM-wiso GCM under mid-Holocene conditions are dynamically downscaled with COSMO_iso for the Arctic region. The capability of COSMO_iso to reproduce observed isotopic ratios in Greenland ice cores for these two periods is investigated by comparing the simulation results to measured δ18O ratios from snow pit samples, Global Network of Isotopes in Precipitation (GNIP) stations and ice cores. To our knowledge, this is the first time that a mid-Holocene isotope-enabled RCM simulation is performed for the Arctic region. Under present-day conditions, a dynamical downscaling of ECHAM5-wiso (1.1∘×1.1∘) with COSMO_iso to a spatial resolution of 50 km improves the agreement with the measured δ18O ratios for 14 of 19 observational data sets. A further increase in the spatial resolution to 7 km does not yield substantial improvements except for the coastal areas with its complex terrain. For the mid-Holocene, a fully coupled MPI-ESM-wiso time slice simulation is downscaled with COSMO_iso to a spatial resolution of 50 km. In the mid-Holocene, MPI-ESM-wiso already agrees well with observations in Greenland and a downscaling with COSMO_iso does not further improve the model–data agreement. Despite this lack of improvement in model biases, the study shows that in both periods, observed δ18O values at measurement sites constitute isotope ratios which are mainly within the subgrid-scale variability of the global ECHAM5-wiso and MPI-ESM-wiso simulation results. The correct δ18O ratios are consequently not resolved in the GCM simulation results and need to be extracted by a refinement with an RCM. In this context, the RCM simulations provide a spatial δ18O distribution by which the effects of local uncertainties can be taken into account in the comparison between point measurements and model outputs. Thus, an isotope-enabled GCM–RCM model chain with realistically implemented fractionating processes constitutes a useful supplement to reconstruct regional paleo-climate conditions during the mid-Holocene in Greenland. Such model chains might also be applied to reveal the full potential of GCMs in other regions and climate periods, in which large deviations relative to observed isotope ratios are simulated.

scholarly journals Sources of holocene variability of oxygen isotopes in paleoclimate archives

2009 ◽  
Vol 5 (2) ◽  
pp. 1133-1162 ◽  
Author(s):  
A. N. LeGrande ◽  
G. A. Schmidt
Keyword(s):  
Water Vapor ◽  
General Circulation ◽  
Ice Sheet ◽  
Circulation Model ◽  
Ice Cores ◽  
Ocean General Circulation Model ◽  
Ocean Basin ◽  
Water Vapor Transport ◽  
Water Isotopes ◽  
Water Isotope

Abstract. Variability in water isotopes has been captured in numerous archives and used to infer climate change. Here we examine water isotope variability over the course of the Holocene using the water-isotope enabled, coupled atmosphere-ocean general circulation model, GISS ModelE-R. Eight Holocene time slices, mostly 1000 years apart are simulated using estimated changes in orbital configuration, greenhouse gases, and ice sheet extent. We find that water isotopes in the model match well with those captured in proxy climate archives in ice cores, ocean sediment cores, and speleothems. The climate changes associated with the water isotope changes, however, are more complex than simple modern analog interpretations. In particular, water isotope variability in Asian speleothems is linked to alterations in landward water vapor transport, not local precipitation, and ice sheet changes over North America lead to masking of temperature signals in Summit, Greenland. Salinity-seawater isotope variability is complicated by inter-ocean basin exchanges of water vapor. Water isotopes do reflect variability in the hydrologic cycle, but are better interpreted in terms of regional changes rather than local climate variables.

scholarly journals The Southern Hemisphere semiannual oscillation and circulation variability during the Mid-Holocene

2010 ◽  
Vol 6 (4) ◽  
pp. 415-430 ◽  
Author(s):  
D. Ackerley ◽  
J. A. Renwick
Keyword(s):  
Southern Hemisphere ◽  
General Circulation ◽  
General Circulation Models ◽  
Atmospheric Variability ◽  
Climatic Effects ◽  
Orbital Parameters ◽  
Ocean General Circulation Models ◽  
Intercomparison Project ◽  
The Tropics ◽  
Semiannual Oscillation

Abstract. The Paleoclimate Modelling Intercomparison Project (PMIP) was undertaken to assess the climatic effects of the presence of large ice-sheets and changes in the Earth's orbital parameters in fully coupled Atmosphere-Ocean General Circulation Models (AOGCMs). Much of the previous literature has focussed on the tropics and the Northern Hemisphere during the last glacial maximum and Mid-Holocene whereas this study focuses only on the Southern Hemisphere. This study addresses the representation of the Semiannual Oscillation (SAO) in the PMIP2 models and how it may have changed during the Mid-Holocene. The output from the five models suggest a weakening of the (austral) autumn circumpolar trough (CPT) and (in all but one model) a strengthening of the spring CPT. The effects of changing the orbital parameters are to cause warming and drying during spring over New Zealand and a cooling and moistening during autumn. The amount of spring warming/drying and autumn cooling/moistening is variable between the models and depends on the climatological locations of surface pressure anomalies associated with changes in the SAO. This study also undertakes an Empirical Orthogonal Function (EOF) analysis of the leading modes of atmospheric variability during the control and Mid-Holocene phases for each model. Despite the seasonal changes, the overall month by month and interannual variability was simulated to have changed little from the Mid-Holocene to present.

Filtering of Milankovitch Cycles by Earth's Geography

1991 ◽  
Vol 35 (2) ◽  
pp. 157-173 ◽  
Author(s):  
David A. Short ◽  
John G. Mengel ◽  
Thomas J. Crowley ◽  
William T. Hyde ◽  
Gerald R. North
Keyword(s):  
Time Series ◽  
General Circulation ◽  
Climate Model ◽  
Temperature Response ◽  
General Circulation Models ◽  
Complex Model ◽  
Milankovitch Cycles ◽  
Seasonal Temperature ◽  
Orbital Forcing ◽  
Model Response

AbstractEarth's land-sea distribution modifies the temperature response to orbitally induced perturbations of the seasonal insolation. We examine this modification in the frequency domain by generating 800,000-yr time series of maximum summer temperature in selected regions with a linear, two-dimensional, seasonal energy balance climate model. Previous studies have demonstrated that this model has a sensitivity comparable to general circulation models for the seasonal temperature response to orbital forcing on land. Although the observed response in the geologic record is sometimes significantly different than modeled here (differences attributable to model limitations and feedbacks involving the ocean-atmosphere-cryosphere system), there are several results of significance: (1) in mid-latitude land areas the orbital signal is translated linearly into a large (>10°C) seasonal temperature response; (2) although the modeled seasonal response to orbital forcing on Antarctica is 6°C, the annual mean temperature effect (<2°C) is only about one-fifth that inferred from the Vostok ice core, and primarily restricted to periods near 41,000 yr; (3) equatorial regions have the richest spectrum of temperature response, with a 3000-yr phase shift in the precession response, plus some power near periods of 10,000–12,000 yr, 41,000 yr, 100,000 yr, and 400,000 yr. Peaks at 10,000–12,000 yr and 100,000 and 400,000 yr result from the twice-yearly passage of the sun across the equator. The complex model response in equatorial regions has some resemblance to geologic time series from this region. The amplification of model response over equatorial land masses at the 100,000-yr period may explain some of the observed large variance in this band in geologic records, especially in pre-Pleistocene records from times of little or no global ice volume.

scholarly journals Simulation of Airborne Impurity Cycles Using Atmospheric General Circulation Models

1985 ◽  
Vol 7 ◽  
pp. 131-137 ◽  
Author(s):  
Sylvie Joussaume
Keyword(s):  
General Circulation ◽  
Ice Sheet ◽  
General Circulation Models ◽  
Dust Particles ◽  
Desert Dust ◽  
Atmospheric General Circulation ◽  
Atmospheric General Circulation Models ◽  
Water Isotope ◽  
Good Agreement

Atmospheric general circulation models are believed to be appropriate tools for studying airborne impurity cycles in order to supplement observations and to improve our knowledge of gaseous and particulate pollutant cycles in the atmosphere. The main aspects of the modelling of tracer cycles are reviewed and illustrated by two particular examples: desert dust particles in the 1 μm range and water isotope species HDO and H218O. Some results from a first simulation including desert dust and water isotope cycles using the model developed at the Laboratoire de Météorologie Dynamique (LMD) are presented and compared to observations, with particular emphasis on ice-sheet data. The relatively good agreement with observations obtained so far is encouraging and should stimulate further applications to other types of tracers.

scholarly journals Simulation of Airborne Impurity Cycles Using Atmospheric General Circulation Models

1985 ◽  
Vol 7 ◽  
pp. 131-137 ◽  
Author(s):  
Sylvie Joussaume
Keyword(s):  
General Circulation ◽  
Ice Sheet ◽  
General Circulation Models ◽  
Dust Particles ◽  
Desert Dust ◽  
Atmospheric General Circulation ◽  
Atmospheric General Circulation Models ◽  
Water Isotope ◽  
Good Agreement

Atmospheric general circulation models are believed to be appropriate tools for studying airborne impurity cycles in order to supplement observations and to improve our knowledge of gaseous and particulate pollutant cycles in the atmosphere. The main aspects of the modelling of tracer cycles are reviewed and illustrated by two particular examples: desert dust particles in the 1 μm range and water isotope species HDO and H2 18O. Some results from a first simulation including desert dust and water isotope cycles using the model developed at the Laboratoire de Météorologie Dynamique (LMD) are presented and compared to observations, with particular emphasis on ice-sheet data. The relatively good agreement with observations obtained so far is encouraging and should stimulate further applications to other types of tracers.

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