Alternative routing of Lake Agassiz overflow during the Younger Dryas: new dates, paleotopography, and a re-evaluation

Teller, James T.; Boyd, Matt; Yang, Zhipeng; Kor, Phillip S.G.; Fard, Amir Mokhtari

doi:10.1016/j.quascirev.2005.01.008

Cited by 110 publications

(108 citation statements)

References 52 publications

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“…This was likely common during times of intermediate ice volume, such as marine isotope stage 3, and may have been the cause for Dansgaard-Oeschger events [Clark et al, 2001]. Recently, the absence of geomorphic evidence for a flood during the YD has been used as the basis to question the role of freshwater forcing of this event [Lowell et al, 2005;Teller et al, 2005;Broecker, 2006], and by extension, of other cold events. Because our results suggest that floods would not cause millennial-scale cold events such as the YD, then the absence of evidence for a YD flood may indeed suggest that such a flood did not occur, perhaps because the lake drained more slowly than assumed, but it cannot be used to question a freshwater-forcing mechanism for the YD.…”

Section: Discussionmentioning

confidence: 99%

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Impact of floods versus routing events on the thermohaline circulation

Meißner

Clark

2006

Geophysical Research Letters

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[1] The last deglaciation was interrupted by three major cooling events, the Younger Dryas, the Preboreal Oscillation and the 8.2-ka cold event. As the Laurentide Ice Sheet retreated, different outlets from Lake Agassiz became available causing the proglacial lake to drain to a new level in a rather short timescale (flood) and divert continental runoff over hundreds of years (routing). Here we use an Earth System Model to investigate the impact of floods (short term, high amplitude) versus routing events (long term, low amplitude) on the thermohaline circulation and the resulting climate change. We show that the initial outbursts of freshwater are not strong enough to influence large-scale climate and can therefore not be the cause of millennial-scale climate variability. However, routing events have the potential of weakening the thermohaline circulation and therefore causing a cool event in the Northern Hemisphere.

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Section: Discussionmentioning

confidence: 99%

“…More recent work, however, has emphasized the role of floods in triggering abrupt climate change Clarke et al, 2003;Teller and Leverington, 2004;Teller et al, 2005;Donnelly et al, 2005;Lowell et al, 2005;LeGrande et al, 2006]. In doing so, it is necessary to assume that the lake-level lowering occurred in months to a year.…”

Section: Introductionmentioning

confidence: 99%

Impact of floods versus routing events on the thermohaline circulation

Meißner

Clark

2006

Geophysical Research Letters

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“…Hypothetically, this massive inflow of freshwater would have reduced North Atlantic Deep Water formation, slowed the global ocean's meridional overturning circulation, and resulted in the abrupt cooling that occurred in less than a century. Although uncertainties remain, such as the exact timing and routing of the drainage (Teller et al 2005, Broecker 2006), glacial lake discharge into the high latitude North Atlantic remains the leading hypothesis for the onset of abrupt climate change associated with the Younger Dryas.…”

Section: Arctic and Global Climate Change In The Pastmentioning

confidence: 99%

Arctic Climate Change and Its Impacts on the Ecology of the North Atlantic

Greene

Pershing

Cronin

et al. 2008

Ecology

117

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Abstract. Arctic climate change from the Paleocene epoch to the present is reconstructed with the objective of assessing its recent and future impacts on the ecology of the North Atlantic. A recurring theme in Earth's paleoclimate record is the importance of the Arctic atmosphere, ocean, and cryosphere in regulating global climate on a variety of spatial and temporal scales. A second recurring theme in this record is the importance of freshwater export from the Arctic in regulating global-to basin-scale ocean circulation patterns and climate. Since the 1970s, historically unprecedented changes have been observed in the Arctic as climate warming has increased precipitation, river discharge, and glacial as well as sea-ice melting. In addition, modal shifts in the atmosphere have altered Arctic Ocean circulation patterns and the export of freshwater into the North Atlantic. The combination of these processes has resulted in variable patterns of freshwater export from the Arctic Ocean and the emergence of salinity anomalies that have periodically freshened waters in the North Atlantic. Since the early 1990s, changes in Arctic Ocean circulation patterns and freshwater export have been associated with two types of ecological responses in the North Atlantic. The first of these responses has been an ongoing series of biogeographic range expansions by boreal plankton, including renewal of the trans-Arctic exchanges of Pacific species with the Atlantic. The second response was a dramatic regime shift in the shelf ecosystems of the Northwest Atlantic that occurred during the early 1990s. This regime shift resulted from freshening and stratification of the shelf waters, which in turn could be linked to changes in the abundances and seasonal cycles of phytoplankton, zooplankton, and higher trophic-level consumer populations. It is predicted that the recently observed ecological responses to Arctic climate change in the North Atlantic will continue into the near future if current trends in sea ice, freshwater export, and surface ocean salinity continue. It is more difficult to predict ecological responses to abrupt climate change in the more distant future as tipping points in the Earth's climate system are exceeded.

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“…A core from the northern Alaskan continental margin (142°W) showed a distinct freshwater spike at *11.5 ka in the isotopic records [2]. That one correlates well in time with another massive outburst of meltwater from glacial Lake Agassiz which went down the Mackenzie River valley and into the Arctic Ocean [34,86]. This low-salinity event may have contributed to the freshening of surface waters in the Nordic Seas which, together with the discharge from the Baltic Ice Lake, triggered the so-called Preboreal Oscillation [35], a brief (max.…”

Section: Last Deglaciationmentioning

confidence: 97%

“…It was suggested that an abrupt change from a southward drainage (to the Mississippi) to a westward discharge through the St. Lawrence River valley at *12.9 ka established a freshwater lid on the northern North Atlantic that reduced or shut down vertical convection and significantly weakened the AMOC. Several authors, however, have claimed a lack of field evidence for large-volume freshwater fluxes in the proposed through-flow regions west of the St. Lawrence River (e.g., [49,86]). Combining results from modeling and field studies, an alternative theory involves a northward routing of freshwater discharge through the Mackenzie valley, entering the Arctic Ocean at 135°W in the Beaufort Sea [57,82,83].…”

Section: Last Deglaciationmentioning

confidence: 99%

The role of Arctic Ocean freshwater during the past 200 ky

Spielhagen

Bauch

2015

Arktos

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As part of the hydrologic cycle, the freshwater system plays a pivotal role for the Arctic Ocean. It maintains the strong stratification in the upper waters and fosters the formation of sea ice on the circum-Arctic shelves from where the ice is being exported toward Fram Strait and into the Nordic Seas. Recent projections of climate change under the greenhouse effect predict severe changes for the hydrologic cycle in the Arctic. This manuscript reviews the current knowledge of past changes in freshwater fluxes to and from the Arctic Ocean and their possible impact on ocean circulation and climate outside the Arctic during the past 200,000 years. It becomes evident that abrupt and large-volume discharges into the Arctic Ocean during times of major climate transitions were capable of disturbing the global ocean circulation and triggering further climate change, e.g., at the onset of the Younger Dryas cold event. During sea-level rise in the Holocene, a connection between the increasing areas available for sea ice formation, the position of the ice margin in the ice export area (the Fram Strait) and the deepwater convection in the Greenland Sea is suggested. Further work is needed to investigate the effects of other catastrophic freshwater discharges from previously ice-dammed lakes in northern Eurasia during the Weichselian and Saalian glaciations. Events like the 8.2 ka and the Younger Dryas, which were associated with flooding and routing of glacial meltwaters and had a significant effect on climate, could serve as a template to better validate the impact of similar occurrences in the past. To date, the actual influence of the earlier events on ocean circulation and climate remains elusive.

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Alternative routing of Lake Agassiz overflow during the Younger Dryas: new dates, paleotopography, and a re-evaluation

Cited by 110 publications

References 52 publications

Impact of floods versus routing events on the thermohaline circulation

Impact of floods versus routing events on the thermohaline circulation

Arctic Climate Change and Its Impacts on the Ecology of the North Atlantic

The role of Arctic Ocean freshwater during the past 200 ky

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