Insights Into Changing Interglacial Conditions in Subarctic Canada From MIS 11 Through MIS 5e From Seasonally Resolved Speleothem Records

High-resolution records from past interglacial climates help constrain future responses to global warming, yet are rare. Here, we produce seasonally resolved climate records from subarctic-Canada using micron-scale measurements of oxygen isotopes (delta 18O) in speleothems with apparent annual growth bands from three interglacial periods-Marine Isotope Stages (MIS) 11, 9, and 5e. We find 3 parts per thousand lower delta 18O values during MIS 11 than MIS 5e, despite MIS 11 likely being warmer. We explore controls on high-latitude speleothem delta 18O and suggest low MIS 11 delta 18O values reflect greater contribution of cold-season precipitation to dripwater from longer annual ground thaw durations. Other potential influences include changes in precipitation source and/or increased fraction of cold-season precipitation from diminished sea ice in MIS 11. Our study highlights the potential for high-latitude speleothems to yield detailed isotopic records of Northern Hemisphere interglacial climates beyond the reach of Greenland ice cores and offers a framework for interpreting them. Few climate records pre-dating the last ice age exist from high-latitude North America, which inhibits our understanding of how regions with permafrost responded to past warming and how they might change in the future. Here, we help fill this data gap by using six speleothems (cave mineral deposits) from a cave in the Northwest Territories, Canada to produce climate records that span thousands of years during former warm periods of Earth's history. We find that speleothems that grew during an exceptionally warm super-interglacial period 400,000 years ago have 3 parts per thousand lower oxygen isotope (delta 18O) values compared to those that grew during a likely cooler interglacial 125,000 years ago. We explore potential explanations for the difference in delta 18O across interglacials, and suggest that lower delta 18O values during warmer periods reflect greater infiltration of cool-season precipitation with longer annual ground thaw durations. This study highlights the importance of high-latitude speleothems to provide detailed climate records beyond the range available from Greenland ice cores. Long high-latitude terrestrial climate records are rare in the Northern Hemisphere High-latitude speleothems can provide ultra-high-resolution climate records beyond the reach of Greenland ice cores Mean oxygen isotopes of Arctic and subarctic speleothems likely are controlled by annual ground thaw durations