Model support for forcing of the 8.2 ka event by meltwater from the Hudson Bay ice dome

Wagner, A. J.; Morrill, C.; Otto‐Bliesner, Bette L.; Rosenbloom, Nan; Watkins, K. R.

doi:10.1007/s00382-013-1706-z

Cited by 41 publications

(39 citation statements)

References 61 publications

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“…These are significantly larger than the forcing of 2.5 Sv for one year (∼0.2 m sea level equivalent) or even than the best estimate of the entire volume of Lake Agassiz (∼0.4 m sea level equivalent). Recent model simulations suggest that the collapse of the Laurentide ice-sheet saddle around 8.2 ka provided this larger volume of freshwater (Gregoire et al, 2012), and that this forcing results in a cooling event that matches many proxy records (Wiersma and Jongma, 2010;Wagner et al, 2013).…”

Section: Discussionmentioning

confidence: 90%

“…There are still some uncertainties regarding the hypothesized forcing of the event, including the volume of drainage from proglacial Lake Agassiz-Ojibway (hereafter Lake Agassiz; Barber et al, 1999) into the Hudson Bay (northeastern Canada) and the possibility of multiple meltwater pulses from both the lake and the collapsing Laurentide Ice Sheet (Teller et al, 2002;Gregoire et al, 2012). Model sensitivity to some of these uncertainties has been explored elsewhere (Renssen et al, 2001;Wiersma et al, 2006;LeGrande and Schmidt, 2008;Clarke et al, 2009;Wiersma and Jongma, 2010;Wagner et al, 2013). The target of this intercomparison is to use a median value for the forcing of the 8.2 ka event and compare model sensitivity to North Atlantic surface buoyancy anomalies that have precise dating and a duration short enough to make simulations with state-of-the-art coupled climate models feasible (Schmidt and LeGrande, 2005;Thomas et al, 2007;Kobashi et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

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Model sensitivity to North Atlantic freshwater forcing at 8.2 ka

Morrill

LeGrande

Renssen³

et al. 2013

Clim. Past

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We compared four simulations of the 8.2 ka event to assess climate model sensitivity and skill in responding to North Atlantic freshwater perturbations. All of the simulations used the same freshwater forcing, 2.5 Sv for one year, applied to either the Hudson Bay (northeastern Canada) or Labrador Sea (between Canada's Labrador coast and Greenland). This freshwater pulse induced a decadal-mean slowdown of 10–25% in the Atlantic Meridional Overturning Circulation (AMOC) of the models and caused a large-scale pattern of climate anomalies that matched proxy evidence for cooling in the Northern Hemisphere and a southward shift of the Intertropical Convergence Zone. The multi-model ensemble generated temperature anomalies that were just half as large as those from quantitative proxy reconstructions, however. Also, the duration of AMOC and climate anomalies in three of the simulations was only several decades, significantly shorter than the duration of ~150 yr in the paleoclimate record. Possible reasons for these discrepancies include incorrect representation of the early Holocene climate and ocean state in the North Atlantic and uncertainties in the freshwater forcing estimates

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Section: Discussionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Model sensitivity to North Atlantic freshwater forcing at 8.2 ka

Morrill

LeGrande

Renssen³

et al. 2013

Clim. Past

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“…The proposed sensitivity experiment (hol8.2k) can use the orbital, ice-sheet, and GHG boundary conditions of the 9.5 ka experiment. The "Lake + Ice_100 years" scenario of Wagner et al (2013) is more consistent with ice dynamics and the data of Carlson et al (2009) than the shorter 1-year flood scenarios and should be adopted for this sensitivity experiment. That is, modeling groups should impose a single input of 2.5 Sv for 1 year followed by a background freshwater flux of 0.13 Sv for 99 years (Table 2).…”

Section: Freshwater Forcingmentioning

confidence: 90%

The PMIP4 contribution to CMIP6 – Part 2: Two interglacials, scientific objective and experimental design for Holocene and Last Interglacial simulations

et al. 2017

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Abstract. Two interglacial epochs are included in the suite of Paleoclimate Modeling Intercomparison Project (PMIP4) simulations in the Coupled Model Intercomparison Project (CMIP6). The experimental protocols for simulations of the mid-Holocene (midHolocene, 6000 years before present) and the Last Interglacial (lig127k, 127 000 years before present) are described here. These equilibrium simulations are designed to examine the impact of changes in orbital forcing at times when atmospheric greenhouse gas levels were similar to those of the preindustrial period and the continental configurations were almost identical to modern ones. These simulations test our understanding of the interplay between radiative forcing and atmospheric circulation, and the connections among large-scale and regional climate changes giving rise to phenomena such as land-sea contrast and highlatitude amplification in temperature changes, and responses of the monsoons, as compared to today. They also provide an opportunity, through carefully designed additional sensitivity experiments, to quantify the strength of atmosphere, ocean, cryosphere, and land-surface feedbacks. Sensitivity experiments are proposed to investigate the role of freshwater forcing in triggering abrupt climate changes within interglacial epochs. These feedback experiments naturally lead to a focus on climate evolution during interglacial periods, which will be examined through transient experiments. Analyses of the sensitivity simulations will also focus on interactions between extratropical and tropical circulation, and the relationship between changes in mean climate state and climate variability on annual to multi-decadal timescales. The comparative abundance of paleoenvironmental data and of quantitative climate reconstructions for the Holocene and Last Interglacial make these two epochs ideal candidates for systematic evaluation of model performance, and such comparisons will shed new light on the importance of external feedbacks (e.g., vegetation, dust) and the ability of state-of-the-art models to simulate climate changes realistically.

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“…Furthermore, the results of climate model simulations for the 8.2 ka event are still ambiguous with respect to the strength and duration of the AMOC slowdown and the following temperature decrease, mostly not matching the proxy evidence (Morrill et al, 2013b). The limitations of climate models in correctly reproducing the full spatio-temporal pattern of climatic changes around 8.2 ka BP are supposedly related to a suite of different factors, involving the complexity and resolution of the models, the probably non-linear response of the AMOC to freshwater forcing (LeGrande and Schmidt, 2008) and a number of not yet well-constrained in-/ external forcings (Morrill et al, 2013b), including the volume and rate of freshwater discharge and its exact routing in the North Atlantic (Li et al, 2009;Morrill et al, 2014;, the possible role of freshwater background forcing from the melting Laurentide Ice Sheet (Matero et al, 2017;Wagner et al, 2013), the ocean circulation mode around 8.2 ka BP (Born and Levermann, 2010;Morrill et al, 2013b) and the early Holocene climate background state (LeGrande et al, 2006). Hence, there still remain many uncertainties regarding the amplitude and pattern of the AMOC slowdown during the 8.2 ka event and its subsequent recovery as well as regarding the associated climatic changes.…”

Section: Introductionmentioning

confidence: 99%

Evidence for higher-than-average air temperatures after the 8.2 ka event provided by a Central European δ18O record

Andersen

Lauterbach

Erlenkeuser

et al. 2017

Quaternary Science Reviews

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a b s t r a c tThe so-called 8.2 ka event represents one of the most prominent cold climate anomalies during the Holocene warm period. Accordingly, several studies have addressed its trigger mechanisms, absolute dating and regional characteristics so far. However, knowledge about subsequent climate recovery is still limited although this might be essential for the understanding of rapid climatic changes. Here we present a new sub-decadally resolved and precisely dated oxygen isotope (d 18 O) record for the interval between 7.7 and 8.7 ka BP (10 3 calendar years before AD 1950), derived from the calcareous valves of benthic ostracods preserved in the varved lake sediments of pre-Alpine Mondsee (Austria). Besides a clear reflection of the 8.2 ka event, showing a good agreement in timing, duration and magnitude with other regional stable isotope records, the high-resolution Mondsee lake sediment record provides evidence for a 75-year-long interval of higher-than-average d 18O values directly after the 8.2 ka event, possibly reflecting increased air temperatures in Central Europe. This observation is consistent with evidence from other proxy records in the North Atlantic realm, thus most probably reflecting a hemispheric-scale climate signal rather than a local phenomenon. As a possible trigger we suggest an enhanced resumption of the Atlantic meridional overturning circulation (AMOC), supporting assumptions from climate model simulations.

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Model support for forcing of the 8.2 ka event by meltwater from the Hudson Bay ice dome

Cited by 41 publications

References 61 publications

Model sensitivity to North Atlantic freshwater forcing at 8.2 ka

Model sensitivity to North Atlantic freshwater forcing at 8.2 ka

The PMIP4 contribution to CMIP6 – Part 2: Two interglacials, scientific objective and experimental design for Holocene and Last Interglacial simulations

Evidence for higher-than-average air temperatures after the 8.2 ka event provided by a Central European δ18O record

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