@article{a7d58bcea6594d4faa987934c80935e0,
title = "Seasonally Resolved Proxy Data From the Antarctic Peninsula Support a Heterogeneous Middle Eocene Southern Ocean",
abstract = "Understanding conditions at both global and local scales during the greenhouse climate of the Eocene Epoch is critical for making accurate predictions in our rapidly warming world. Despite the wealth of proxy data and modeling studies, fundamental aspects of the climate system still remain uncertain. For example, accurate austral high-latitude temperatures are necessary to understand the evolution of temperatures during the lead-up to Antarctic glaciation and determine the meridional temperature gradient during greenhouse warmth, yet records are few and disparate. Here we present seasonally resolved temperature and precipitation data from the latest Lutetian (~42 Ma) from the eastern Antarctic Peninsula. Oxygen isotopes from bivalves indicate a mean temperature of 13.1 °C and a seasonal range of 8.0 °C, slightly (<1 °C) more seasonal than modeled temperatures from high-obliquity simulations. Carbon isotopes from driftwood suggest that summer accounts for just over half of annual precipitation. When compared with other austral high-latitude records, the data are consistent with a zonally heterogeneous middle Eocene Southern Ocean. Similar longitudinal variability is observed in the modern boreal high latitudes, where landmasses subdivide the ocean, subjecting basins to their own distinct circulation patterns and coastal processes. With closed Drake and Tasman passages, the middle Eocene Southern Ocean would also have been noncontiguous, resulting in larger variability of sea surface temperatures along individual zonal bands than today. This interpretation resolves inconsistencies among existing high-austral proxy records and suggests that the large seasonal range of temperatures may be indicative of regional-scale circulation patterns along the peninsula not captured by low-resolution climate simulations.",
keywords = "Antarctica, climate model, middle Eocene, sea surface temperature, seasonality, stable isotope geochemistry",
author = "Judd, {Emily J.} and Ivany, {Linda C.} and DeConto, {Robert M.} and Halberstadt, {Anna Ruth W.} and Miklus, {Nicole M.} and Junium, {Christopher K.} and Uveges, {Benjamin T.}",
note = "Funding Information: Research was funded by NSF Antarctic Earth Science PLR‐1543031 (to L. C. I.), and by grants from Sigma Xi and GSA (to E. J. J.) and the SU Department of Earth Sciences (to E. J. J. and N. M. M.). Samples were originally collected during fieldwork funded by OPP‐ 9908828 to Richard Aronson and OPP‐ 9908856 to Daniel Blake; specimens are housed at Syracuse University. We thank Lindsay Moon for assistance in micromilling, Lora Wingate at the University of Michigan Stable Isotope Lab and David Dettman at the University of Arizona Environmental Isotope Laboratory for performing isotope analyses, Edward Berry at the State University of New York—Upstate for assisting with X‐Ray diffraction analyses, and Wanyi Lu and Zunli Lu for help with trace element analyses. We also thank Hope Jahren and Brian Schubert for guidance regarding interpretation of the driftwood data. Willem Sijp provided helpful discussion and insight at an early stage of this work. Tripti Bhattacharya and James Muirhead read the manuscript and offered thoughtful feedback. We thank the two anonymous reviewers, whose feedback improved the clarity and content of the manuscript. Oxygen isotope data can be found in the supporting information or through the US Antarctic Program Data Center (USAP‐DC; http://www.usap‐dc.org/ view/dataset/601174). GCM simulation output files (http://www.usap‐dc.org/ view/dataset/601175) and organic carbon isotope data (http://www.usap-dc.org/view/dataset/601173) are also available through USAP‐DC. Funding Information: Research was funded by NSF Antarctic Earth Science PLR-1543031 (to L. C. I.), and by grants from Sigma Xi and GSA (to E. J. J.) and the SU Department of Earth Sciences (to E. J. J. and N. M. M.). Samples were originally collected during fieldwork funded by OPP-9908828 to Richard Aronson and OPP-9908856 to Daniel Blake; specimens are housed at Syracuse University. We thank Lindsay Moon for assistance in micromilling, Lora Wingate at the University of Michigan Stable Isotope Lab and David Dettman at the University of Arizona Environmental Isotope Laboratory for performing isotope analyses, Edward Berry at the State University of New York?Upstate for assisting with X-Ray diffraction analyses, and Wanyi Lu and Zunli Lu for help with trace element analyses. We also thank Hope Jahren and Brian Schubert for guidance regarding interpretation of the driftwood data. Willem Sijp provided helpful discussion and insight at an early stage of this work. Tripti Bhattacharya and James Muirhead read the manuscript and offered thoughtful feedback. We thank the two anonymous reviewers, whose feedback improved the clarity and content of the manuscript. Oxygen isotope data can be found in the supporting information or through the US Antarctic Program Data Center (USAP-DC;?http://www.usap-dc.org/view/dataset/601174). GCM simulation output files (http://www.usap-dc.org/view/dataset/601175) and organic carbon isotope data (http://www.usap-dc.org/view/dataset/601173) are also available through USAP-DC. Publisher Copyright: {\textcopyright}2019. American Geophysical Union. All Rights Reserved.",
year = "2019",
month = may,
doi = "10.1029/2019PA003581",
language = "English (US)",
volume = "34",
pages = "787--799",
journal = "Paleoceanography and Paleoclimatology",
issn = "2572-4517",
publisher = "American Geophysical Union",
number = "5",
}