Abrupt Bølling‐Allerød Warming Simulated under Gradual Forcing of the Last Deglaciation

Obase, Takashi; Abe‐Ouchi, Ayako

doi:10.1029/2019gl084675

Cited by 65 publications

(77 citation statements)

References 66 publications

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“…In the present study, the experiments have been carried out with the coupled atmosphere-ocean general circulation model, MIROC4m, a mid-resolution model developed jointly by the Center for Climate System Research (CCSR), National Institute for Environmental Studies (NIES) and Frontier Research Center for Global Change (FRCGC), in Japan (K-1 model developers, 2004). This model has previously been used to study a variety of climate states, for example, future RCP4.5 and RCP8.5 scenarios (Bakker et al, 2016), the mid-Holocene (Ohgaito et al, 2013), the Last Glacial Maximum (Yanase and Abe-Ouchi, 2007), and the mPWP (Chan et al, 2011). The same model with a higher resolution was included in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC, 2013).…”

Section: Model Descriptionmentioning

confidence: 99%

Pliocene Model Intercomparison Project (PlioMIP2) simulations using the Model for Interdisciplinary Research on Climate (MIROC4m)

Chan

Abe‐Ouchi

2020

Clim. Past

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Abstract. The second phase of the Pliocene Model Intercomparison Project (PlioMIP2) has attracted many climate modelling groups in its continuing efforts to better understand the climate of the mid-Piacenzian warm period (mPWP) when atmospheric CO2 was last closest to present-day levels. Like the first phase, PlioMIP1, it is an internationally coordinated initiative that allows for a systematic comparison of various models in a similar manner to the Paleoclimate Modelling Intercomparison Project (PMIP). Model intercomparison and model–data comparison now focus specifically on the interglacial at marine isotope stage KM5c (3.205 Ma), and experimental design is not only based on new boundary conditions but includes various sensitivity experiments. In this study, we present results from long-term model integrations using the MIROC4m (Model for Interdisciplinary Research on Climate) atmosphere–ocean coupled general circulation model, developed at the institutes CCSR, NIES and FRCGC in Japan. The core experiment, with CO2 levels set to 400 ppm, shows a warming of 3.1 ∘C compared to the pre-industrial period, with two-thirds of the warming being attributed to the increase in CO2. Although this level of warming is less than that in the equivalent PlioMIP1 experiment, there is slightly better agreement with proxy sea surface temperature (SST) data at PRISM3 (PRISM – Pliocene Research Interpretation and Synoptic Mapping) locations, especially in the northern North Atlantic where there were large model–data discrepancies in PlioMIP1. Similar spatial changes in precipitation and sea ice are seen and the Arctic remains ice-free in the summer in the core experiments of both phases. Comparisons with both the proxy SST data and proxy surface air temperature data from paleobotanical sites indicate a weaker polar amplification in model results. Unlike PlioMIP1, the Atlantic Meridional Overturning Circulation (AMOC) is now stronger than that of the pre-industrial period, even though increasing CO2 tends to weaken it. This stronger AMOC is a consequence of a closed Bering Strait in the PlioMIP2 paleogeography. Also, when present-day boundary conditions are replaced by those of the Pliocene, the dependency of the AMOC strength on CO2 is significantly weakened. Sensitivity tests show that lower values of CO2 give a global SST which is overall more consistent with the PRISM3 SST field presented in PlioMIP1, while SSTs at many of the PRISM4 sites are still too high to be reconciled with any of the model results. On the other hand, tropical Pacific SST in the core experiment agrees well with more recent proxy data, which suggested that PRISM3 SST there was overestimated. Future availability of climate reconstructions from proxy data will continue to help evaluate model results. The inclusion of dynamical vegetation and the effects of all possible extreme orbital configurations outside KM5c should be considered in future experiments using MIROC4m for the mPWP.

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Section: Model Descriptionmentioning

confidence: 99%

Pliocene Model Intercomparison Project (PlioMIP2) simulations using the Model for Interdisciplinary Research on Climate (MIROC4m)

Chan

Abe‐Ouchi

2020

Clim. Past

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“…It was driven by the collapse of vulnerable ice sheet sectors, and was concurrent with rapid Northern Hemispheric warming and disruptions in oceanic and atmospheric circulation 3 , 4 . The ice-ocean-climate feedbacks operating during this period are not well understood largely due to a lack of consensus on the sources of MWP-1A 5 , 6 , which, in turn, were likely to be a key driver in stimulating rapid deglacial climate change 7 – 9 .…”

Section: Introductionmentioning

confidence: 99%

A reconciled solution of Meltwater Pulse 1A sources using sea-level fingerprinting

et al. 2021

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The most rapid global sea-level rise event of the last deglaciation, Meltwater Pulse 1A (MWP-1A), occurred ∼14,650 years ago. Considerable uncertainty regarding the sources of meltwater limits understanding of the relationship between MWP-1A and the concurrent fast-changing climate. Here we present a data-driven inversion approach, using a glacio-isostatic adjustment model to invert for the sources of MWP-1A via sea-level constraints from six geographically distributed sites. The results suggest contributions from Antarctica, 1.3 m (0–5.9 m; 95% probability), Scandinavia, 4.6 m (3.2–6.4 m) and North America, 12.0 m (5.6–15.4 m), giving a global mean sea-level rise of 17.9 m (15.7–20.2 m) in 500 years. Only a North American dominant scenario successfully predicts the observed sea-level change across our six sites and an Antarctic dominant scenario is firmly refuted by Scottish isolation basin records. Our sea-level based results therefore reconcile with field-based ice-sheet reconstructions.

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“…Many of these studies show a strengthening of the AMOC in response to the expansion of the northern glacial ice sheet (Eisenman et al, 2009;Brady et al, 2013;Zhang et al, 2014a;Gong et al, 2015;Klockmann et al, 2016;Brown and Galbraith, 2016;Kawamura et al, 2017), whereas one study shows a reduction of the AMOC (Kim, 2004). From sensitivity experiments, it is clearly shown that the higher Northern American glacial ice sheets enhance the surface wind as well as the wind-driven oceanic transport of salt into the deep-water formation region over the North Atlantic, which increases the surface salinity and causes a strengthening of the AMOC (Oka et al, 2012;Muglia and Schmittner, 2015;Sherriff-Tadano et al, 2018). Other studies also suggest the importance of changes in surface cooling (Smith and Gregory, 2012), which can cause either a strengthening of the AMOC by enhancing deep-water formation over the North Atlantic (Schmittner et al, 2002;Oka et al, 2012;Smith and Gregory, 2012) or a weakening of the AMOC by increasing the amount of sea ice over the northern North Atlantic and Southern Ocean (Kawamura et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Impact of mid-glacial ice sheets on deep ocean circulation and global climate

2021

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Abstract. This study explores the effect of southward expansion of Northern Hemisphere (American) mid-glacial ice sheets on the global climate and the Atlantic Meridional Overturning Circulation (AMOC) as well as the processes by which the ice sheets modify the AMOC. For this purpose, simulations of Marine Isotope Stage (MIS) 3 (36 ka) and 5a (80 ka) are performed with an atmosphere–ocean general circulation model. In the MIS3 and MIS5a simulations, the global average temperature decreases by 5.0 and 2.2 ∘C, respectively, compared with the preindustrial climate simulation. The AMOC weakens by 3 % in MIS3, whereas it strengthens by 16 % in MIS5a, both of which are consistent with an estimate based on 231Pa ∕ 230Th. Sensitivity experiments extracting the effect of the southward expansion of glacial ice sheets from MIS5a to MIS3 show a global cooling of 1.1 ∘C, contributing to about 40 % of the total surface cooling from MIS5a to MIS3. These experiments also demonstrate that the ice sheet expansion leads to a surface cooling of 2 ∘C over the Southern Ocean as a result of colder North Atlantic Deep Water. We find that the southward expansion of the mid-glacial ice sheet exerts a small impact on the AMOC. Partially coupled experiments reveal that the global surface cooling by the glacial ice sheet tends to reduce the AMOC by increasing the sea ice at both poles and, hence, compensates for the strengthening effect of the enhanced surface wind over the North Atlantic. Our results show that the total effect of glacial ice sheets on the AMOC is determined by two competing effects: surface wind and surface cooling. The relative strength of surface wind and surface cooling effects depends on the ice sheet configuration, and the strength of the surface cooling can be comparable to that of surface wind when changes in the extent of ice sheet are prominent.

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Abrupt Bølling‐Allerød Warming Simulated under Gradual Forcing of the Last Deglaciation

Cited by 65 publications

References 66 publications

Pliocene Model Intercomparison Project (PlioMIP2) simulations using the Model for Interdisciplinary Research on Climate (MIROC4m)

Pliocene Model Intercomparison Project (PlioMIP2) simulations using the Model for Interdisciplinary Research on Climate (MIROC4m)

A reconciled solution of Meltwater Pulse 1A sources using sea-level fingerprinting

Impact of mid-glacial ice sheets on deep ocean circulation and global climate

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