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  • 1
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    PANGAEA
    In:  Supplement to: Song, Zhaoyang; Latif, Mojib; Park, Wonsun (2019): East Atlantic Pattern Drives Multidecadal Atlantic Meridional Overturning Circulation Variability During the Last Glacial Maximum. Geophysical Research Letters, 46(19), 10865-10873, https://doi.org/10.1029/2019GL082960
    Publication Date: 2023-01-13
    Description: The variability of the Atlantic Meridional Overturning Circulation (AMOC) and its governing processes during the Last Glacial Maximum (LGM) is investigated in the Kiel Climate Model (KCM). Under LGM conditions, enhanced multidecadal AMOC variability is simulated relative to a preindustrial control run and surface heat flux variability linked to the East Atlantic pattern the primary driver of AMOC variability. In contrast, the multidecadal AMOC variability in the preindustrial control simulation is mainly driven by surface heat flux variability associated with the North Atlantic Oscillation (NAO). Stand-alone atmosphere model experiments show that the difference in mechanism is tightly linked to the differences in topography. The stronger multidecadal AMOC variability suggested by the KCM may be an important additional factor to understanding abrupt climate changes over the North Atlantic sector during the LGM.
    Type: Dataset
    Format: application/zip, 613.9 kBytes
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  • 2
    Publication Date: 2023-01-13
    Description: Long-term predictability of the North Atlantic sea surface temperature (SST) is commonly attributed to buoyancy-forced changes of the Atlantic Meridional Overturning Circulation. Here we investigate the role of surface wind stress forcing in decadal hindcasts as another source of extratropical North Atlantic SST predictability. For this purpose, a global climate model is forced by reanalysis (ERA-interim) wind stress anomalies over the period 1979-2017. The simulated climate states serve as initial conditions for decadal hindcasts. Significant skill in predicting detrended observed annual SST anomalies is observed over the extratropical central North Atlantic with anomaly correlation coefficients exceeding 0.6 at lead times of 4 to 7 years. The skill is insensitive to the calendar month of initialization and linked to upper-ocean heat content anomalies that lead anomalous SSTs by several years.
    Keywords: Binary Object; Binary Object (File Size); Binary Object (Media Type); Description
    Type: Dataset
    Format: text/tab-separated-values, 36 data points
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  • 3
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    PANGAEA
    In:  Supplement to: Song, Zhaoyang; Latif, Mojib; Park, Wonsun (2017): Expanding Greenland Ice Sheet Enhances Sensitivity of Plio-Pleistocene Climate to Obliquity Forcing in the Kiel Climate Model. Geophysical Research Letters, https://doi.org/10.1002/2017GL074835
    Publication Date: 2023-01-13
    Description: Proxy data suggest that the Plio-Pleistocene transition from ~3.2 - 3.0 to 2.5 Ma featured the onset of Northern Hemisphere glaciation and enhanced climate variability on obliquity timescale. Here, we investigate the influence of the expanding Greenland ice sheet (GrIS) on the mean climate and obliquity-related variability. Special attention is given to the Atlantic Meridional Overturning Circulation (AMOC). A series of climate model simulations suggest that the expanding GrIS weakens the AMOC by ~1 Sv, which is mainly due to reduced heat loss of the Greenland-Iceland-Norwegian Sea. Moreover, the expanded GrIS amplifies the Hadley circulation response to obliquity forcing. This drives enhanced obliquity-forced variations in freshwater export from the tropical Atlantic and in turn variations of the AMOC that increase by about a factor. The stronger AMOC response to obliquity forcing in turn drives a stronger global-mean near-surface temperature response. We conclude that the AMOC response to obliquity forcing is important to understand the enhanced climate variability on obliquity timescale during the Plio-Pleistocene transition.
    Keywords: File content; File format; File name; File size; Uniform resource locator/link to model result file
    Type: Dataset
    Format: text/tab-separated-values, 50 data points
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  • 4
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    PANGAEA
    In:  Supplement to: Song, Zhaoyang; Latif, Mojib; Park, Wonsun; Zhang, Yuming (2018): Influence of Model Bias on Simulating North Atlantic Sea Surface Temperature During the Mid-Pliocene. Paleoceanography and Paleoclimatology, https://doi.org/10.1029/2018PA003397
    Publication Date: 2023-02-24
    Description: Climate models generally underestimate the pronounced warming in the sea surface temperature (SST) over the North Atlantic during the mid-Pliocene that is suggested by proxy data. Here, we investigate the influence of the North Atlantic cold SST bias, which is observed in many climate models, on the simulation of mid-Pliocene surface climate in a series of simulations with the Kiel Climate Model. A surface freshwater-flux correction is applied over the North Atlantic, which considerably enhances simulation of North Atlantic Ocean circulation and SST under present-day conditions. Using reconstructed mid-Pliocene boundary conditions with closed Bering and Arctic Archipelago Straits, the corrected model depicts significantly reduced model-proxy SST discrepancy in comparison to the uncorrected model. A key factor in reducing the discrepancy is the stronger and more sensitive Atlantic Meridional Overturning Circulation and poleward heat transport. We conclude that simulations of mid-Pliocene surface climate over the North Atlantic can considerably benefit from alleviating model biases in this region.
    Keywords: File format; File name; File size; GEOMAR; Helmholtz Centre for Ocean Research Kiel; Uniform resource locator/link to file
    Type: Dataset
    Format: text/tab-separated-values, 20 data points
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  • 5
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    PANGAEA
    In:  Supplement to: Zhang, Xiao; Prange, Matthias; Steph, Silke; Butzin, Martin; Krebs, Uta; Lunt, Daniel J; Nisancioglu, Kerim H; Park, Wonsun; Schmittner, Andreas; Schneider, Birgit; Schulz, Michael (2012): Changes in equatorial Pacific thermocline depth in response to Panamanian seaway closure: Insights from a multi-model study. Earth and Planetary Science Letters, 317-318, 76-84, https://doi.org/10.1016/j.epsl.2011.11.028
    Publication Date: 2023-05-25
    Description: The early Pliocene warm phase was characterized by high sea surface temperatures and a deep thermocline in the eastern equatorial Pacific. A new hypothesis suggests that the progressive closure of the Panamanian seaway contributed substantially to the termination of this zonally symmetric state in the equatorial Pacific. According to this hypothesis, intensification of the Atlantic meridional overturning circulation (AMOC) - induced by the closure of the gateway - was the principal cause of equatorial Pacific thermocline shoaling during the Pliocene. In this study, twelve Panama seaway sensitivity experiments from eight ocean/climate models of different complexity are analyzed to examine the effect of an open gateway on AMOC strength and thermocline depth. All models show an eastward Panamanian net throughflow, leading to a reduction in AMOC strength compared to the corresponding closed-Panama case. In those models that do not include a dynamic atmosphere, deepening of the equatorial Pacific thermocline appears to scale almost linearly with the throughflow-induced reduction in AMOC strength. Models with dynamic atmosphere do not follow this simple relation. There are indications that in four out of five models equatorial wind-stress anomalies amplify the tropical Pacific thermocline deepening. In summary, the models provide strong support for the hypothesized relationship between Panama closure and equatorial Pacific thermocline shoaling.
    Keywords: File content; File format; File name; File size; Uniform resource locator/link to file
    Type: Dataset
    Format: text/tab-separated-values, 30 data points
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  • 6
    Publication Date: 2023-09-01
    Description: Stable oxygen isotope records from central Greenland suggest disproportionally large long-term surface-air temperature (SAT) variability during the last glacial maximum (LGM) relative to preindustrial times. Large perturbations in mean atmospheric circulation and its variability forced by extensive Northern Hemisphere ice sheet coverage has been suggested as cause for the enhanced Greenland SAT variability. Here, we assess the factors driving Greenland SAT variability during the LGM by means of dedicated climate model simulations and find remote forcing from the Pacific of critical importance. Atmospheric teleconnections from the Interdecadal Pacific Oscillation (IPO), a multidecadal oscillation of sea-surface temperature in the Pacific Ocean, strongly intensify under LGM conditions, driving enhanced surface wind variability over Greenland, which in turn amplifies SAT variability by anomalous atmospheric heat transport. A major role of the IPO in forcing Greenland SAT variability also is supported by a number of models from the Paleoclimate Modelling Intercomparison Project Phase III.
    Keywords: Binary Object; Binary Object (File Size); Binary Object (Media Type); Description; LGM; Paleo Modelling; PalMod
    Type: Dataset
    Format: text/tab-separated-values, 26 data points
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  • 7
    Publication Date: 2014-06-24
    Description: The early Pliocene warm phase was characterized by high sea surface temperatures and a deep thermocline in the eastern equatorial Pacific. A new hypothesis suggests that the progressive closure of the Panamanian seaway contributed substantially to the termination of this zonally symmetric state in the equatorial Pacific. According to this hypothesis, intensification of the Atlantic meridional overturning circulation (AMOC) – induced by the closure of the gateway – was the principal cause of equatorial Pacific thermocline shoaling during the Pliocene. In this study, twelve Panama seaway sensitivity experiments from eight ocean/climate models of different complexity are analyzed to examine the effect of an open gateway on AMOC strength and thermocline depth. All models show an eastward Panamanian net throughflow, leading to a reduction in AMOC strength compared to the corresponding closed-Panama case. In those models that do not include a dynamic atmosphere, deepening of the equatorial Pacific thermocline appears to scale almost linearly with the throughflow-induced reduction in AMOC strength. Models with dynamic atmosphere do not follow this simple relation. There are indications that in four out of five models equatorial wind-stress anomalies amplify the tropical Pacific thermocline deepening. In summary, the models provide strong support for the hypothesized relationship between Panama closure and equatorial Pacific thermocline shoaling.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 8
    Publication Date: 2017-01-27
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
    Publication Date: 2021-07-22
    Description: The variability of the Atlantic meridional overturning circulation (AMOC) and its governing processes during the Last Glacial Maximum (LGM) is investigated in the Kiel Climate Model. Under LGM conditions, multidecadal AMOC variability is mainly forced by the surface heat flux variability linked to the East Atlantic pattern (EAP). In contrast, the multidecadal AMOC variability under preindustrial conditions is mainly driven by the surface heat flux variability associated with the North Atlantic Oscillation. Stand-alone atmosphere model experiments show that relative to preindustrial conditions, the change in AMOC forcing under LGM conditions is tightly linked to the differences in topography.
    Keywords: 551.6
    Language: English
    Type: article
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  • 10
    Publication Date: 2021-07-21
    Description: Stable oxygen isotope records from central Greenland suggest disproportionally large long‐term surface air temperature (SAT) variability during the Last Glacial Maximum (LGM) relative to preindustrial times. Large perturbations in mean atmospheric circulation and its variability forced by extensive Northern Hemisphere ice sheet coverage have been suggested as cause for the enhanced Greenland SAT variability. Here, we assess the factors driving Greenland SAT variability during the LGM by means of dedicated climate model simulations and find remote forcing from the Pacific of critical importance. Atmospheric teleconnections from the Interdecadal Pacific Oscillation (IPO), a multidecadal oscillation of sea surface temperature in the Pacific Ocean, strongly intensify under LGM conditions, driving enhanced surface wind variability over Greenland, which in turn amplifies SAT variability by anomalous atmospheric heat transport. A major role of the IPO in forcing Greenland SAT variability also is supported by a number of models from the Paleoclimate Modeling Intercomparison Project Phase III.
    Description: Plain Language Summary: Stable oxygen isotope records, a proxy for the local surface air temperature (SAT), from central Greenland indicate disproportionally large reductions in the multidecadal variability from the Last Ice Age (Last Glacial Maximum, LGM; about 21,000 years before present) to modern times. A climate model simulates the changes in multidecadal Greenland SAT variability as inferred from the proxy data. The enhanced variability during the LGM is largely remotely driven by the Interdecadal Pacific Oscillation (IPO), a multidecadal oscillation of sea surface temperature (SST) in the Pacific Ocean. Atmospheric teleconnections from the IPO strongly intensify under glacial conditions, driving enhanced surface wind variability over Greenland and through atmospheric heat transport the SAT variability.
    Description: Key Points: Oxygen isotope records and climate modeling show large reductions in Greenland surface temperature variability from the LGM to modern times Atmospheric teleconnections from the Interdecadal Pacific Oscillation intensify under glacial conditions Greenland surface temperature is forced by atmospheric heat transport and sea ice linked to the Interdecadal Pacific Oscillation
    Keywords: 551.6 ; climate modeling ; Greenland ; surface temperature variability ; Interdecadal Pacific Oscillation ; atmospheric heat transport ; atmospheric teleconnections
    Type: article
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