Decadal to seasonal changes in oxygen isotopes across Dansgaard-Oeschger events from speleothems in the mid-continent of North America

The connection between abrupt high-latitude warming during the last glacial period and rapid temperature/hydrologic changes at lower latitudes has revealed strong inter-hemispheric teleconnections in the ocean–atmosphere system. How this connection influenced climate in the midcontinent of North America is unclear because climate archives with sufficient time resolution are scarce. This study investigates paleoclimate changes ~70–45 thousand years ago (ka) across multiple timescales (sub-annual to millennial) from speleothems in southern Wisconsin and Minnesota (USA). To do this we use fluorescent imaging (confocal laser microscopy) and a secondary ion mass spectrometer (SIMS) to collect high-resolution δ¹⁸O measurements (5-10µm) across individual stalagmite growth bands. Annual growth bands are 20-80 µm in width, allowing for subannual sampling resolution. Abrupt climate changes that were previously identified in a stalagmite from this region (Batchelor et al. 2023) are recorded as several large (2.0 to 3.0‰), negative δ¹⁸O excursions that occurred between 61–55 ka, coinciding with Dansgaard–Oeschger (DO) events 17–14. Here we extend the record from our prior work by 10 ka from a higher accumulation rate speleothem. Our high-resolution δ¹⁸O SIMS data show similar large (1 to 1.5‰) δ¹⁸O shifts during DO events 13 and 12 that occur in less than 30 years. When comparing the intra-annual δ¹⁸O gradient measured in different fluorescent bands, we observe a weaker gradient during DO interstadials, and a stronger gradient during DO stadials suggesting that seasonal changes in the hydrological system are also occurring during these events. Our results demonstrate large, abrupt temperature and hydrological responses to DO events during the last glacial period in midcontinent North America and indicate a strong seasonal climate response to DO warming and cooling. At the meeting we will present our published and unpublished measurements and related modeling simulations.