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  • 1
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    Middle Miocene Climate and Stable Oxygen Isotopes in Europe Based on Numerical Modeling (2022)
    Details
    Publication Date: 2023-11-24
    Description: The Middle Miocene (15.99–11.65 Ma) of Europe witnessed major climatic, environmental, and vegetational change, yet we are lacking detailed reconstructions of Middle Miocene temperature and precipitation patterns over Europe. Here, we use a high‐resolution (∼0.75°) isotope‐enabled general circulation model (ECHAM5‐wiso) with time‐specific boundary conditions to investigate changes in temperature, precipitation, and δ〈sup〉18〈/sup〉O in precipitation (δ〈sup〉18〈/sup〉O〈sub〉p〈/sub〉). Experiments were designed with variable elevation configurations of the European Alps and different atmospheric CO〈sub〉2〈/sub〉 levels to examine the influence of Alpine elevation and global climate forcing on regional climate and δ〈sup〉18〈/sup〉Op patterns. Modeling results are in agreement with available paleobotanical temperature data and with low‐resolution Middle Miocene experiments of the Miocene Model Intercomparison Project (MioMIP1). However, simulated precipitation rates are 300–500 mm/yr lower in the Middle Miocene than for pre‐industrial times for central Europe. This result is consistent with precipitation estimates from herpetological fossil assemblages, but contradicts precipitation estimates from paleobotanical data. We attribute the Middle Miocene precipitation change in Europe to shifts in large‐scale pressure patterns in the North Atlantic and over Europe and associated changes in wind direction and humidity. We suggest that global climate forcing contributed to a maximum δ〈sup〉18〈/sup〉O〈sub〉p〈/sub〉 change of ∼2‰ over high elevation (Alps) and ∼1‰ over low elevation regions. In contrast, we observe a maximum modeled δ〈sup〉18〈/sup〉O〈sub〉p〈/sub〉 decrease of 8‰ across the Alpine orogen due to Alpine topography. However, the elevation‐δ〈sup〉18〈/sup〉O〈sub〉p〈/sub〉 lapse rate shallows in the Middle Miocene, leading to a possible underestimation of paleotopography when using present‐day δ〈sup〉18〈/sup〉O〈sub〉p〈/sub〉—elevation relationships data for stable isotope paleoaltimetry studies.
    Description: Key Points: A high‐resolution isotope‐enabled general circulation model is used to explore Middle Miocene climate and precipitation δ〈sup〉18〈/sup〉O across Europe. Middle Miocene bi‐directional precipitation change consistent with herpetological fossils and account for precipitation δ〈sup〉18〈/sup〉O variations. Global Miocene climate forcing contributed a max δ〈sup〉18〈/sup〉O change of ∼2‰ over the high Alpine elevation and to ∼1‰ over low elevation.
    Description: German research fondation
    Description: Alexander‐von‐Humboldt foundation, Feodor‐Lynen‐Fellowship
    Description: Alexander‐von‐Humboldt foundation, Humboldt Research Fellowship
    Description: Scientific Steering Committee
    Description: https://mpimet.mpg.de/fileadmin/projekte/ICON-ESM/mpi-m_sla_201202.pdf
    Description: https://gitlab.awi.de/mwerner/mpi-esm-wiso
    Description: https://zenodo.org/record/6308475#.Y0gmDSFS-2w
    Keywords: ddc:550.724 ; Europe ; Middle Miocene ; climate modeling ; stable water isotopes ; temperature ; precipitation ; paleoclimate ; paleoelevation ; Alps
    Language: English
    Type: doc-type:article
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  • 2
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    The Impact of Different Atmospheric CO2 Concentrations on Large Scale Miocene Temperature Signatures (2023)
    Hossain, Akil ; Knorr, Gregor ; Jokat, Wilfried ; [et al.]
    Details
    Publication Date: 2023-11-23
    Description: Based on inferences from proxy records the Miocene (23.03–5.33 Ma) was a time of amplified polar warmth compared to today. However, it remains a challenge to simulate a warm Miocene climate and pronounced polar warmth at reconstructed Miocene CO〈sub〉2〈/sub〉 concentrations. Using a state‐of‐the‐art Earth‐System‐Model, we implement a high‐resolution paleobathymetry and simulate Miocene climate at different atmospheric CO〈sub〉2〈/sub〉 concentrations. We estimate global mean surface warming of +3.1°C relative to the preindustrial at a CO〈sub〉2〈/sub〉 level of 450 ppm. An increase of atmospheric CO〈sub〉2〈/sub〉 from 280 to 450 ppm provides an individual warming of ∼1.4°C, which is as strong as all other Miocene forcing contributions combined. Substantial changes in surface albedo are vital to explain Miocene surface warming. Simulated surface temperatures fit well with proxy reconstructions at low‐ to mid‐latitudes. The high latitude cooling bias becomes less pronounced for higher atmospheric CO〈sub〉2〈/sub〉 concentrations. At such CO〈sub〉2〈/sub〉 levels simulated Miocene climate shows a reduced polar amplification, linked to a breakdown of seasonality in the Arctic Ocean. A pronounced warming in boreal fall is detected for a CO〈sub〉2〈/sub〉 increase from 280 to 450 ppm, in comparison to weaker warming for CO〈sub〉2〈/sub〉 changes from 450 to 720 ppm. Moreover, a pronounced warming in winter is detected for a CO〈sub〉2〈/sub〉 increase from 450 to 720 ppm, in contrast to a moderate summer temperature increase, which is accompanied by a strong sea‐ice concentration decline that promotes cloud formation in summer via enhanced moisture availability. As a consequence planetary albedo increases and dampens the temperature response to CO〈sub〉2〈/sub〉 forcing at a warmer Miocene background climate.
    Description: Key Points: At a CO〈sub〉2〈/sub〉 level of 450 ppm, a Miocene simulation shows a global mean surface warming of +3.1°C relative to the preindustrial state. Atmospheric CO〈sub〉2〈/sub〉 increase from 280 to 450 ppm causes a warming of ∼1.4°C, which is as strong as all other forcing factors combined. At higher atmospheric CO〈sub〉2〈/sub〉 levels, the Miocene climate shows a reduced polar amplification linked to a breakdown of seasonality in the Arctic.
    Description: Alfred Wegener Institute
    Description: Helmholtz Centre for Polar and Marine Research
    Description: https://doi.org/10.1594/PANGAEA.943430
    Description: https://github.com/FESOM/fesom2/
    Description: https://mpimet.mpg.de/en/science/modeling-with-icon/code-avilability
    Keywords: atmospheric CO2 ; Miocene ; Miocene temperature change ; polar amplification ; climate modeling ; Miocene bathymetry
    Language: English
    Type: doc-type:article
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  • 3
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    East Asian summer precipitation in AWI‐CM3: Comparison with observations and CMIP6 models (2023)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2023-11-13
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Owing to the complicated spatial–temporal characteristics of East Asian precipitation (EAP), climate models have limited skills in simulating the modern Asian climate. This consequently leads to large uncertainties in simulations of the past EAP variation and future projections. Here, we explore the performance of the newly developed Alfred Wegener Institute Climate Model, version 3 (AWI‐CM3) in simulating the climatological summer EAP. To test whether the model's skill depends on its atmosphere resolution, we design two AWI‐CM3 simulations with different horizontal resolutions. The result shows that both simulations have acceptable performance in simulating the summer mean EAP, generally better than the majority of individual models participating in the Coupled Model Intercomparison Project (CMIP6). However, for the monthly EAP from June to August, AWI‐CM3 exhibits a decayed skill, which is due to the subseasonal movement of the western Pacific subtropical high bias. The higher‐resolution AWI‐CM3 simulation shows an overall improvement relative to the one performed at a relatively lower resolution in all aspects taken into account regarding the EAP. We conclude that AWI‐CM3 is a suitable tool for exploring the EAP for the observational period. Having verified the model's skill for modern climate, we suggest employing the AWI‐CM3, especially with high atmosphere resolution, both for applications in paleoclimate studies and future projections.〈/p〉
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉This figure shows the skill scores of AWI‐CM3 and CMIP6 models in simulating the climatological summer East Asian precipitation (EAP), which indicates that AWI‐CM3 simulations perform better than most CMIP6 individual models for the summer mean EAP, while AWI‐CM3's skills decay from June to August.〈boxed-text position="anchor" content-type="graphic" id="joc8075-blkfxd-0001" xml:lang="en"〉 〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:08998418:media:joc8075:joc8075-toc-0001"〉 〈alt-text〉image〈/alt-text〉 〈/graphic〉 〈/boxed-text〉〈/p〉
    Description: National Natural Science Foundation of China http://dx.doi.org/10.13039/501100001809
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: Helmholtz Climate Initiative REKLIM
    Description: Helmholtz Program
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Description: China Scholarship Council http://dx.doi.org/10.13039/501100004543
    Description: https://opendata.dwd.de/climate_environment/GPCC/html/fulldata-monthly_v2022_doi_download.html
    Description: https://crudata.uea.ac.uk/cru/data/hrg/cru_ts_4.05
    Description: http://aphrodite.st.hirosaki-u.ac.jp/products.html
    Description: https://jra.kishou.go.jp/JRA-55/index_en.html
    Description: https://esgf-node.llnl.gov/search/cmip6
    Keywords: ddc:551.6 ; AWI‐CM3 ; CMIP6 ; East Asia ; summer precipitation
    Language: English
    Type: doc-type:article
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  • 4
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    Agreement between reconstructed and modeled boreal precipitation of the Last Interglacial (2019)
    American Association for the Advancement of Science (AAAS)
    In:  Science Advances, 5 (11). Art.Nr. eaax7047.
    Details
    Publication Date: 2021-01-08
    Description: The last extended time period when climate may have been warmer than today was during the Last Interglacial (LIG; ca. 129 to 120 thousand years ago). However, a global view of LIG precipitation is lacking. Here, seven new LIG climate models are compared to the first global database of proxies for LIG precipitation. In this way, models are assessed in their ability to capture important hydroclimatic processes during a different climate. The models can reproduce the proxy-based positive precipitation anomalies from the preindustrial period over much of the boreal continents. Over the Southern Hemisphere, proxy-model agreement is partial. In models, LIG boreal monsoons have 42% wider area than in the preindustrial and produce 55% more precipitation and 50% more extreme precipitation. Austral monsoons are weaker. The mechanisms behind these changes are consistent with stronger summer radiative forcing over boreal high latitudes and with the associated higher temperatures during the LIG.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1126/sciadv.aax7047
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Abrupt climate and weather changes across time scales (2020)
    AGU (American Geophysical Union)
    Details
    Publication Date: 2023-02-08
    Description: The past provides evidence of abrupt climate shifts and changes in the frequency of climate and weather extremes. We explore the non‐linear response to orbital forcing and then consider climate millennial variability down to daily weather events. Orbital changes are translated into regional responses in temperature, where the precessional response is related to nonlinearities and seasonal biases in the system. We question regularities found in climate events by analyzing the distribution of inter‐event waiting times. Periodicities of about 900 and 1150 years are found in ice cores besides the prominent 1500‐years cycle. However, the variability remains indistinguishable from a random process, suggesting that centennial‐to‐millennial variability is stochastic in nature. New numerical techniques are developed allowing for a high resolution in the dynamically relevant regions like coasts, major upwelling regions, and high latitudes. Using this model, we find a strong sensitivity of the Atlantic meridional overturning circulation depending on where the deglacial meltwater is injected into. Meltwater into the Mississippi and near Labrador hardly affect the large‐scale ocean circulation, whereas subpolar hosing mimicking icebergs yields a quasi shutdown. The same multi‐scale approach is applied to radiocarbon simulations enabling a dynamical interpretation of marine sediment cores. Finally, abrupt climate events also have counterparts in the recent climate records, revealing a close link between climate variability, the statistics of North Atlantic weather patterns, and extreme events.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    A salty deep ocean as a prerequisite for glacial termination (2021)
    Nature Research
    Details
    Publication Date: 2024-02-07
    Description: Abstract Deglacial transitions of the middle to late Pleistocene (terminations) are linked to gradual changes in insolation accompanied by abrupt shifts in ocean circulation. However, the reason these deglacial abrupt events are so special compared with their sub-glacial-maximum analogues, in particular with respect to the exaggerated warming observed across Antarctica, remains unclear. Here we show that an increase in the relative importance of salt versus temperature stratification in the glacial deep South Atlantic decreases the potential cooling effect of waters that may be upwelled in response to abrupt perturbations in ocean circulation, as compared with sub-glacial-maximum conditions. Using a comprehensive coupled atmosphere–ocean general circulation model, we then demonstrate that an increase in deep-ocean salinity stratification stabilizes relatively warm waters in the glacial deep ocean, which amplifies the high southern latitude surface ocean temperature response to an abrupt weakening of the Atlantic meridional overturning circulation during deglaciation. The mechanism can produce a doubling in the net rate of warming across Antarctica on a multicentennial timescale when starting from full glacial conditions (as compared with interglacial or subglacial conditions) and therefore helps to explain the large magnitude and rapidity of glacial terminations during the late Quaternary.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Simulated ocean velocity at 420 m water depth for pre-industrial, glacial, Pliocene, and Miocene climate states (2018)
    PANGAEA
    Details
    Publication Date: 2023-04-12
    Description: We provide global fields of simulated ocean velocity in zonal (netCDF variable UKO) and meridional (netCDF variable VKE) direction at a depth of 420 m. Six climate states are covered in the data set: 1. data set PI_mpiom_UKO_VKE_timmean_420m.nc: pre-industrial (PI) control state (representative for 1850 AD) as used in the publications by Stepanek and Lohmann (2012) and Zhang et al. (2013). The respective data is courtesy of Zhang et al. (2013) 2. data set LGM_mpiom_UKO_VKE_timmean_420m.nc: a climate state of the Last Glacial Maximum (simulation LGM-W by Zhang et al., 2013), representative for 21 kiloyears (ka) before present (BP) 3. data set Plio_mpiom_UKO_VKE_timmean_420m.nc: a climate state of the Mid-Pliocene Warm Period (simulation experiment 2 by Stepanek and Lohmann, 2012), that covers the time from 3.29 - 2.97 million years (Ma) BP 4. data set MIO_mpiom_UKO_VKE_timmean_420m.nc: a climate state representing conditions of the early to middle Miocene (23 to 15 Ma BP) including a regional bathymetry reconstruction (15 Ma) of the North Atlantic / Arctic Ocean by Ehlers and Jokat (2013) and considering 450 ppm of carbon dioxide (simulation EO450 by Stärz et al., 2017) 5. data set MioW_mpiom_UKO_VKE_timmean_420m.nc: a climate state representing conditions of the early to middle Miocene (23 to 15 Ma BP) including a regional bathymetry reconstruction (15 Ma) of the Weddell Sea (Huang et al., 2014) and considering 450 ppm of carbon dioxide in the atmosphere (simulation MIOW_450 by Huang et al., 2017) 6. data set MioW_PIS_mpiom_UKO_VKE_timmean_420m.nc: a climate state similar to 5. but with PI (278 ppm) carbon dioxide concentration and prescribed modern ice sheets (simulation MIOW_PIS by Huang et al., 2017) All data sets represent climatological annual averages over a time period of 100 years. The oceanography is based on climate simulations performed with the Community Earth System Models (COSMOS) that consist of the atmosphere general circulation model ECHAM5 (Roeckner et al., 2003), internally coupled to the land surface and terrestrial carbon cycle model JSBACH (Raddatz et al., 2007) in T31 resolution (3.75°x3.75°) with 19 vertical levels on a hybrid sigma-pressure coordinate, and the ocean general circulation model MPIOM (Marsland et al., 2003) on a bipolar curvilinear GR30 grid with a formal resolution of 3.0°x1.8° and 40 z-coordinate levels. Exchange of momentum, mass, and energy between the atmosphere and ocean domain is enabled via the OASIS3 coupler (Valcke et al., 2003). For all simulations, ocean characteristics (including sea ice) and properties of atmosphere and land (including the land carbon cycle and dynamic vegetation) are computed based on the prescribed climate forcing (concentration of atmospheric trace gases, configuration of the Earth's orbit) and boundary conditions (land surface elevation, ice sheets, ocean bathymetry, and land sea mask). For details of the utilized boundary conditions and climate forcing refer to the original publications describing the data (Stepanek and Lohmann, 2012; Zhang et al., 2013; Huang et al., 2017; Stärz et al., 2017). In case of analyzing velocities of the Arctic Ocean, note that for few grid cells in the northernmost data row (89.5°N), between 280°E and 293°E, there is a data artifact in variable VKE. This artifact is a side effect of rotating and interpolatiing velocities from the curvilinear model grid to a standard NSWE coordinate system; this artifact has not been removed from the data sets.
    Keywords: AWI_PaleoClimate; File format; File name; File size; Paleo-climate Dynamics @ AWI; Uniform resource locator/link to file
    Type: Dataset
    Format: text/tab-separated-values, 24 data points
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    DATA PANGAEA
  • 8
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    Results of calculated surface air temperature anomaly of COSMOS Pliocene experiment 2 in NetCDF format
    PANGAEA
    In:  Supplement to: Stepanek, Christian; Lohmann, Gerrit (2012): Modelling mid-Pliocene climate with COSMOS. Geoscientific Model Development, 5(5), 1221-1243, https://doi.org/10.5194/gmd-5-1221-2012
    Details
    Publication Date: 2023-06-24
    Description: In this manuscript we describe the experimental procedure employed at the Alfred Wegener Institute in Germany in the preparation of the simulations for the Pliocene Model Intercomparison Project (PlioMIP). We present a description of the utilized Community Earth System Models (COSMOS, version: COSMOS-landveg r2413, 2009) and document the procedures that we applied to transfer the Pliocene Research, Interpretation and Synoptic Mapping (PRISM) Project mid-Pliocene reconstruction into model forcing fields. The model setup and spin-up procedure are described for both the paleo- and preindustrial (PI) time slices of PlioMIP experiments 1 and 2, and general results that depict the performance of our model setup for mid-Pliocene conditions are presented. The mid-Pliocene, as simulated with our COSMOS setup and PRISM boundary conditions, is both warmer and wetter in the global mean than the PI. The globally averaged annual mean surface air temperature in the mid-Pliocene standalone atmosphere (fully coupled atmosphere-ocean) simulation is 17.35 °C (17.82 °C), which implies a warming of 2.23 °C (3.40 °C) relative to the respective PI control simulation.
    Type: Dataset
    Format: application/zip, 189.9 kBytes
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    DATA PANGAEA
  • 9
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    Orbitally forced simulated surface air temperature of the last 1,000,000 years (2020)
    PANGAEA
    Details
    Publication Date: 2023-12-07
    Description: We provide a climatic data set of the history of annual mean surface air temperature (SAT) over the last 1,000,000 years. The SAT (i.e. the temperature at 2 meter height above the ground) has been simulated by means of the Community Earth System Models (COSMOS, consisting of ECHAM5, JSBACH, MPIOM). These have been exposed to the solution of elements of the Earth's orbit around the sun (eccentricity, obliquity, longitude of the perihelion) by Laskar et al. (2004) for the last 1,000,000 years. Towards practical feasibility of the climate simulation, the orbital forcing has been accelerated by a factor of 100 based on the method described by Lorenz and Lohmann (2004). A detailed description of the COSMOS' application in the framework of paleoclimate can be found, for example, in the publication by Stepanek and Lohmann (2012).
    Keywords: climate simulation; last 1 000 000 years; Orbital forcing; Paleoclimate; Paleo Modelling; PalMod
    Type: Dataset
    Format: application/x-netcdf, 176 MBytes
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    DATA PANGAEA
  • 10
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    Compiled Mg/Ca data from PlioVAR (2023)
    PANGAEA
    Details
    Publication Date: 2023-12-18
    Keywords: 130-806A; 130-806B; 165-999A; 184-1143B; 184-1143C; 202-1241; 202-1241A; 202-1241B; 202-1241C; 22-214; 306-U1313B; 306-U1313C; Age; alkenone SST; benthic and planktonic foraminifers; Caribbean Sea; COMPCORE; Composite Core; d18O of planktic foraminifera; Date/Time of event; Depth, composite; DEPTH, sediment/rock; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Event label; Exp306; Extracted from PlioVAR KM5c SST Database; Foraminifera, planktic, Magnesium/Calcium ratio; foraminifera oxygen isotopes; From literature; Glomar Challenger; Indian Ocean//RIDGE; Joides Resolution; Latitude of event; Leg130; Leg165; Leg184; Leg202; Leg22; Literature search; Longitude of event; Mg/Ca-based sea surface temperature; North Atlantic Climate 2; Northern Hemisphere glaciation; North Pacific Ocean; PAGES_PlioVAR; Pleistocene; Pliocene; PlioVAR - Pliocene climate variability over glacial-interglacial timescales; Reference/source; Sample code/label; Sea surface temperature; Site; South China Sea; Species, unique identification; Species, unique identification (Semantic URI); Species, unique identification (URI); Uniform resource locator/link to raw data file; Uniform resource locator/link to reference
    Type: Dataset
    Format: text/tab-separated-values, 26274 data points
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    DATA PANGAEA
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