POST-LGM LANDSCAPE RESPONSE: INCREASED CHEMICAL WEATHERING, ATMOSPHERIC CO2 CONSUMPTION, AND GLACIAL ISOSTATIC ADJUSTMENT

Rapid landscape and climatic changes resulting from continental-scale deglaciation produced a chemical weathering pulse of sufficient intensity to influence global atmospheric carbon dioxide (CO₂) levels. Post-Little Ice Age (LIA) lake chronosequence data suggest a ~200-300 year period of increased chemical weathering on newly deglaciated terrains, resulting in a CO₂ consumption rate of 10⁶ moles CO₂/km²/yr; an order of magnitude higher than the present-day global average. Coupled with post-Last Glacial Maximum (LGM) land exposure rates (≥2000 km²/yr) from UMISM (University of Maine Ice Sheet Model) solutions, this rapid chemical weathering of highly reactive glacial detritus resulted in a significant negative feedback to warming (consumption >10¹² moles CO₂/yr by the end of the Younger Dryas). In addition to rapid geochemical changes, these landscapes concurrently undergo glacial isostatic adjustment (uplift of up to 32 mm/yr in post-LIA sites) upon deglaciation. The coupling of these short-wavelength, dynamic responses to deglaciation is crucial to fully characterizing the system. While existing models of glacial-interglacial shifts in global terrestrial chemical weathering rates have shown no significant effect on atmospheric CO₂ over timescales of ≥500,000 years, further research on short-term (≤200 yr) dynamics is needed to better constrain and, ultimately, model the geochemical evolution of the post-LGM Northern Hemisphere.