Amplified North Atlantic Little Ice Age Cooling Inferred From Inversion of Benthic Foraminiferal Records

Abstract Paleoceanographic reconstructions indicate a large‐scale cooling in the last millennium, but significant disagreement on the spatial pattern and timing still exists. This disagreement is partially due to the inference of surface conditions from sparse, noisy, near‐surface marine fauna that exhibit seasonal and habitat depth biases. Here, we infer spatially‐varying surface changes from benthic sediment core records by back‐propagation through an ocean circulation model, improving upon prior methodologies that inferred regional surface evolution from subsurface records. We present a surface temperature and history that fits 11 high‐resolution benthic records within error and also supports previous independent estimates from Common Era marine surface records. Our methodology accounts for the opposing and covarying behavior of temperature and on , as well as age model uncertainty. Our estimate is characterized by a high‐latitude (N) North Atlantic‐centered Little Ice Age sea surface temperature (SST) cooling of 0.38 0.13 K (1 s.e.) from 1140 to 1880 CE, which is within error of planktonic SST record compilations and exceeds the cooling exhibited in the Last Millennium Reanalysis. We improve the detection of long‐term climate signals by using benthic sediment core records which record the properties of abyssal waters that are not subject to high‐energy near‐surface variability, instead of planktonic sediment core records which tend to have more noise. These results are consistent with the global SST trends inferred from the Ocean2k planktonic SST compilation and corroborate robust Little Ice Age cooling in the North Atlantic, while providing further insights on its spatial pattern.