Climate Change during Marine Isotope Stages 10 & 11 based on High-Resolution Speleothem Records from Eastern North America

Abstract:

Two speleothems from eastern North America grew throughout Marine Isotope Stages 10 and 11. High-resolution stable isotope δ¹⁸O and δ¹³C, and Sr records are constrained by 16 ²³⁰Th age dates. MIS 11 (374 – 424 kyr BP) is of particular interest due to the similarity of orbitally-controlled insolation conditions from this time period and the modern. While few high-resolution continental paleoclimate records exist for this time period, marine records reveal that during this prominent interglacial, sea surface temperatures were relatively stable, in contrast to those which occurred during the subsequent glacial period (MIS 10).

Speleothems TNBS-8 and TNMOR2-01, from Tennessee’s Blue Springs Cave and Morrell Cave, respectively, grew between 338 – 420 kyr BP and overlap for ~50 kyr. Growth rates were generally higher during MIS 11 than 10, with a higher degree of variability. Stable isotope δ¹⁸O and δ¹³C records (TNMOR2-01) show an overall trend towards higher values throughout the MIS 11-10 transition, with well-defined periods of depletion and enrichment. Sr concentration measured through µ-XRF reveals similar behavior as the δ¹³C record and serves as a proxy for moisture availability. Overlapping Sr results for both speleothems share general trends and reveal distinct intervals of increased precipitation occur throughout the record, with most coinciding with summer insolation maxima. The transitions of MIS 11.2 to 11.1 and MIS 11 to 10 are well-constrained by abrupt increases in δ¹⁸O and δ¹³C values along with Sr concentrations.

An examination of continental proxy responses to similar orbital and climatic conditions as the modern allows for not only a greater understanding of how the climate changed during the MIS 10-11, but also allows for the examination of natural climate variability in light of the addition of anthropogenic climate forcing.