Rapid northern hemisphere ice sheet melting during the penultimate deglaciation

Abstract

The rate and consequences of future high latitude ice sheet retreat remain a major concern given ongoing anthropogenic warming. Here, new precisely dated stalagmite data from NW Iberia provide the first direct, high-resolution records of periods of rapid melting of Northern Hemisphere ice sheets during the penultimate deglaciation. These records reveal the penultimate deglaciation initiated with rapid century-scale meltwater pulses which subsequently trigger abrupt coolings of air temperature in NW Iberia consistent with freshwater-induced AMOC slowdowns. The first of these AMOC slowdowns, 600-year duration, was shorter than Heinrich 1 of the last deglaciation. Although similar insolation forcing initiated the last two deglaciations, the more rapid and sustained rate of freshening in the eastern North Atlantic penultimate deglaciation likely reflects a larger volume of ice stored in the marine-based Eurasian Ice sheet during the penultimate glacial in contrast to the land-based ice sheet on North America as during the last glacial.

Carbonates in the Critical Zone

“…Lechleitner et al (2021) show that an increase in soil gas pCO 2 is recorded in speleothem carbon isotope (δ 13 C spel ), which may retain information on soil respiration. Similarly, Stoll et al (2022), attribute trends in δ 13 C spel to soil gas and bedrock dissolution. They propose that higher temperatures increase vegetation productivity, thereby increasing soil CO 2 production, which leads to more negative δ 13 C in speleothems.…”

“…Open and closed conditions are partly dictated by the water saturation state of the pore spaces, with complete water saturation producing closed conditions. Whether carbonate dissolution proceeds under open or closed conditions impacts both the rate of weathering processes (Buhmann & Dreybrodt, 1985a, 1985b) and trace element concentrations and isotopic compositions of dissolved species (Hendy, 1971; Stoll et al., 2022). A global study of spring water chemistry suggests that, on average, spring chemistry in carbonate regions is well‐explained by weathering under conditions that are open to soil CO 2 (Romero‐Mujalli et al., 2019).…”

Distinguishing the vegetation and soil component of δ13C variation in speleothem records from degassing and prior calcite precipitation effects

“…Despite site to site heterogeneity, individual drips monitored over an 18 month period show very limited temporal variation in Mg/Sr ratios despite order of magnitude differences in drip rate, suggesting that in this cave, individual drips sample a relatively stable bedrock dissolution source. For most stalagmites, age models are published previously, including those for GAE, GAL, and GLO (Stoll et al, 2015;Stoll et al, 2013), GAR and GUL (Stoll et al, 2022).…”

Carbonates in the Critical Zone

“…Open and closed conditions are partly dictated by the water saturation state of the pore spaces, with complete water saturation producing closed conditions. Whether carbonate dissolution proceeds under open or closed conditions impacts both the rate of weathering processes (Buhmann & Dreybrodt, 1985a;Buhmann & Dreybrodt, 1985b) and trace element concentrations and isotopic compositions of dissolved species (Hendy, 1971;Stoll et al, 2022). A global study of spring water chemistry suggests that, on average, spring chemistry in carbonate regions is well-explained by weathering under conditions that are open to soil CO2 (Romero-Mujalli et al, 2019).…”

“…Lechleitner et al (2021) show that an increase in soil gas pCO2 is recorded in speleothem carbon isotope (δ 13 Cspel), which may retain information on soil respiration. Similarly, Stoll et al (2022), attribute trends in δ 13 Cspel to soil gas and bedrock dissolution. They propose that higher temperatures increase vegetation productivity, thereby increasing soil CO2 production, which leads to more negative δ 13 C in speleothems.…”