Geochemical proxies of North American freshwater routing during the Younger Dryas cold event

On the reconstruction of palaeo-ice sheets: Recent advances and future challenges

“…Opinions differ about precise timing and routing of GLA overflow during the YD, because different approaches often yield different interpretations (e.g. deVernal et al, 1996;Tarasov and Peltier, 2005;Carlson et al, 2007;Murton et al, 2010;Not and Hillaire-Marcel, 2012;Cronin et al, 2012;Carlson and Clark, 2012). In a recent review, Carlson and Clark (2012) favoured an easterly route, but numerical modelling suggests a large influx of freshwater into the Arctic Ocean was more likely (although not necessarily from GLA: Tarasov and Peltier, 2005), and would have had a more significant impact on ocean circulation (Condron and Winsor, 2012).…”

“…In the outer St Lawrence Estuary, there is microfaunal and geochemical evidence for hydrological changes, possibly caused by GLA drainage, near the onset of the Younger Dryas ~ 13 ka (Rodrigues and Vilks, 1994;Jones, 1995, de Vernal et al, 1996;Carlson et al 2007). In the central St. Lawrence Lowlands and the Lake Champlain Basin to the south (regions that are closer to the LIS margin and mid-continental proglacial lakes), the evidence is even more convincing.…”

Oxygen isotope geochemistry of Laurentide ice-sheet meltwater across Termination I

“…Several studies have interpreted the residual d 18 O sw value in terms of relative salinity changes, variations in the hydrologic cycle, or surface water hydrography (Carlson et al, 2007;Hoffman et al, 2012;Obbink et al, 2010;Schmidt et al, 2004Schmidt et al, , 2006Thornalley et al, 2011 (Bowen and Wilkinson, 2002). During the last deglaciation, the d 18 O w value of Mississippi River discharge into the Gulf of Mexico was determined by two factors: a d 18 O signal of continental precipitation integrated over the watershed, and seasonal contributions of meltwater from the melting LIS.…”

“…Oxygen isotope analyses of marine sedimentary records proximal to LIS meltwater outflow offer the most direct evidence of the isotopic evolution of the LIS, and help to constrain the location and timing of routing of meltwater (e.g., Aharon, 2003Aharon, , 2006Broecker et al, 1989;Carlson, 2009;Carlson et al, 2007;Flower et al, 2004;Hill et al, 2006;Hoffman et al, 2012;Keigwin et al, 1991;Williams et al, 2012). However, mixing models of meltwater contributions to the ocean typically assume a constant d 18 O w value for the LIS (À25 or À35‰; Aharon, 2006;Carlson, 2009;Carlson et al, 2007;Hill et al, 2006;Obbink et al, 2010), and do not attempt to incorporate the complex spatial heterogeneity in d 18 O w observed in modern continental ice sheets (Masson-Delmotte et al, 2008;Vinther et al, 2009).…”

“…However, mixing models of meltwater contributions to the ocean typically assume a constant d 18 O w value for the LIS (À25 or À35‰; Aharon, 2006;Carlson, 2009;Carlson et al, 2007;Hill et al, 2006;Obbink et al, 2010), and do not attempt to incorporate the complex spatial heterogeneity in d 18 O w observed in modern continental ice sheets (Masson-Delmotte et al, 2008;Vinther et al, 2009). Attempts to estimate the oxygen isotope composition of parts of the LIS have used measurements of remnant ice such as the Barnes Ice Cap (Hooke, 1976;Hooke and Clausen, 1982), Pleistocene-age groundwater (Hooke and Clausen, 1982;Remenda et al, 1994) and preserved ice wedges (Kotler and Burn, 2000); as well as indirect proxies from subglacial carbonates (Refsnider et al, 2012(Refsnider et al, , 2014 and proglacial lakes (Birks et al, 2007;Buhay and Betcher, 1998;Last et al, 1994;Moore et al, 2000).…”