What drives LGM precipitation over the western Mediterranean? A study focused on the Iberian Peninsula and northern Morocco

Beghin, Pauline; Charbit, S.; Kageyama, Masa; Nebout, Nathalie Combourieu; Hatté, Christine; Dumas, Christophe; Peterschmitt, Jean-Yves

doi:10.1007/s00382-015-2720-0

Cited by 54 publications

(49 citation statements)

References 83 publications

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“…The maximum of the corresponding parabola yields a better approximation of the exact latitude of the maximum jet wind. This method allows for a more accurate finding of the latitude of the jet maximum (Chavaillaz et al, 2013;Beghin et al, 2015). We find a good linear correlation between the shift of the North Atlantic jet and the Scandinavian precipitation anomaly during the winter season (Fig.…”

Section: Precipitation Changes Over Scandinavia: Implication Of the Jmentioning

confidence: 56%

“…Using the PMIP3 model outputs for the LGM and the PI time slices, Beghin et al (2015) found a correlation between the southward shift of the North Atlantic jet stream from the preindustrial to the LGM periods and the winter precipitation changes over the Iberian Peninsula. Following the same approach, we examine whether a similar mechanism to the one found in (Beghin et al, 2015) may explain the precipitation changes over Scandinavia when the LIS characteristics (albedo and topography) are modified. Similarly to Chavaillaz et al (2013), we use the 850 hPa zonal wind to define the jet stream.…”

Section: Precipitation Changes Over Scandinavia: Implication Of the Jmentioning

confidence: 98%

“…The recent inter-comparison study of the North Atlantic jet stream in LGM vs. pre-industrial conditions in the PMIP3 coupled models (Braconnot et al, 2012) carried out by Beghin et al (2015) clearly shows that the response of the jet stream to LGM conditions is highly model-dependent. This latter study confirms the range of various results found in the recent literature.…”

Section: Ocean-atmosphere Interactionsmentioning

confidence: 99%

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How might the North American ice sheet influence the northwestern Eurasian climate?

et al. 2015

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Abstract.It is now widely acknowledged that past Northern Hemisphere ice sheets covering Canada and northern Europe at the Last Glacial Maximum (LGM) exerted a strong influence on climate by causing changes in atmospheric and oceanic circulations. In turn, these changes may have impacted the development of the ice sheets themselves through a combination of different feedback mechanisms. The present study is designed to investigate the potential impact of the North American ice sheet on the surface mass balance (SMB) of the Eurasian ice sheet driven by simulated changes in the past glacial atmospheric circulation. Using the LMDZ5 atmospheric circulation model, we carried out 12 experiments under constant LGM conditions for insolation, greenhouse gases and ocean. In these experiments, the Eurasian ice sheet is removed. The 12 experiments differ in the North American ice-sheet topography, ranging from a white and flat (present-day topography) ice sheet to a fullsize LGM ice sheet. This experimental design allows the albedo and the topographic impacts of the North American ice sheet onto the climate to be disentangled. The results are compared to our baseline experiment where both the North American and the Eurasian ice sheets have been removed. In summer, the sole albedo effect of the American ice sheet modifies the pattern of planetary waves with respect to the no-ice-sheet case, resulting in a cooling of the northwestern Eurasian region. By contrast, the atmospheric circulation changes induced by the topography of the North American ice sheet lead to a strong decrease of this cooling. In winter, the Scandinavian and the Barents-Kara regions respond differently to the American ice-sheet albedo effect: in response to atmospheric circulation changes, Scandinavia becomes warmer and total precipitation is more abundant, whereas the Barents-Kara area becomes cooler with a decrease of convective processes, causing a decrease of total precipitation. The gradual increase of the altitude of the American ice sheet leads to less total precipitation and snowfall and to colder temperatures over both the Scandinavian and the Barents and Kara sea sectors. We then compute the resulting annual surface mass balance over the Fennoscandian region from the simulated temperature and precipitation fields used to force an ice-sheet model. It clearly appears that the SMB is dominated by the ablation signal. In response to the summer cooling induced by the American ice-sheet albedo, high positive SMB values are obtained over the Eurasian region, leading thus to the growth of an ice sheet. On the contrary, the gradual increase of the American ice-sheet altitude induces more ablation over the Eurasian sector, hence limiting the growth of Fennoscandia. To test the robustness of our results with respect to the Eurasian ice sheet state, we carried out two additional LMDZ experiments with new boundary conditions involving both the American (flat or full LGM) and high Eurasian ice sheets. The most striking result is that the Eurasian ice sheet is...

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Section: Precipitation Changes Over Scandinavia: Implication Of the Jmentioning

confidence: 56%

Section: Precipitation Changes Over Scandinavia: Implication Of the Jmentioning

confidence: 98%

Section: Ocean-atmosphere Interactionsmentioning

confidence: 99%

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How might the North American ice sheet influence the northwestern Eurasian climate?

et al. 2015

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“…Storm tracks, jet stream, and Intertropical Convergence Zone (ITCZ) meridional shifts may also be linked to sea surface temperature/surface air temperature changes in the North Atlantic (e.g. Beghin et al, ; Brayshaw et al, ; Park et al, ), but evidence for this mechanism in our simulations is inconclusive. A set of specific sensitivity studies using a hierarchy of models (including higher spatial resolution and idealized simulations) would be needed, in order to analyze quantitatively the potential mechanism linking both monsoons and storm track dynamics on precessional time scales.…”

Section: Implications For the Interpretation Of The Sedimentary Recordmentioning

confidence: 74%

Precessional Drivers of Late Miocene Mediterranean Sedimentary Sequences: African Summer Monsoon and Atlantic Winter Storm Tracks

Marzocchi

Flecker

Lunt

et al. 2019

Paleoceanog and Paleoclimatol

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Cyclic sedimentary patterns in the marine record of the Mediterranean Sea have been consistently correlated with orbitally-driven shifts in climate. Freshwater input driven by the African summer monsoon is thought to be the main control of such hydrological changes, where the runoff signal is transferred from the eastern to the western Mediterranean. The geological record from the Atlantic margin also contains precession-driven dilution cycles that have been correlated with the sedimentary sequences in the western and eastern Mediterranean despite the lack of a direct connection with the basin. In these regions, Atlantic winter storms have also been invoked to explain the wet phases. In the absence of seasonally-resolved proxy data, climate simulations at high temporal resolution can be used to investigate the drivers of Mediterranean hydrologic changes both on precessional and seasonal timescales. Here, we use the results of 22 ocean-atmosphere-vegetation simulations through an entire late Miocene precession cycle. These show that the African summer monsoon drives the hydrologic budget in the Eastern Mediterranean during precession minima, while the western marginal basins are generally dominated by local net evaporative loss. During precession minima, the western Mediterranean and the Atlantic margin are also influenced by enhanced winter precipitation from the Atlantic storm tracks. We can, therefore, identify two different moisture sources affecting the circum-Mediterranean area, characterized by the same phasing with respect to precession, but with opposite seasonality. This supports the interregional correlation of geological sections in these areas, as we show for the Messinian and speculate for other time periods.

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“…If the westerlies had shifted south (north), this may have led to a reduction (an increase) in eastward sea ice transport to the region of NADW formation, and thus modify the strength (or perhaps the sign) of the sea ice process. Since the meridional shift of the westerlies in response to glacial ice sheets depends on the model (Laîné et al 2009;Rivière et al 2010;Hofer et al 2012;Merz et al 2015;Beghin et al 2015) and the configuration of the ice sheets (Kageyama et al 1999, Li andBattisiti 2008;Laîné et al 2009;Beghin et al 2015), the effect of the sea ice process related to the meridional shift of the westerlies should also depend largely on individual simulations. More studies are required to understand the precise role of the sea ice process related to the meridional shift of the westerlies.…”

Section: Discussionmentioning

confidence: 99%

Influence of glacial ice sheets on the Atlantic meridional overturning circulation through surface wind change

et al. 2017

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What drives LGM precipitation over the western Mediterranean? A study focused on the Iberian Peninsula and northern Morocco

Abstract: International audienc

Cited by 54 publications

References 83 publications

How might the North American ice sheet influence the northwestern Eurasian climate?

How might the North American ice sheet influence the northwestern Eurasian climate?

Precessional Drivers of Late Miocene Mediterranean Sedimentary Sequences: African Summer Monsoon and Atlantic Winter Storm Tracks

Influence of glacial ice sheets on the Atlantic meridional overturning circulation through surface wind change

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