International Research Fellowship Program: The Hunt for Sea-Ice Proxies: Evolution and Paleoceology of Archaeomonads

Kulhanek Denise K, Lincoln NE

Investigators

Abstract

1005400 Kulhanek The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support a twenty-four-month research fellowship by Dr. Denise K. Kulhanek to work with Dr. Richard W. Jordan at Yamagata University in Japan. Reconstruction of past sea-ice duration and extent is a major objective of polar paleoceanographers, as sea ice plays an important role within the modern climate system. The recent reduction of summer Arctic sea-ice cover and how this will affect future climate makes it even more important to understand the mechanisms through which sea ice first formed in polar regions, and how it has changed over time. Reconstructions of Quaternary sea-ice extent are quite robust as they utilize extant microorganisms as sea-ice proxies; however, extending these proxies into older sediments characterized by extinct taxa is difficult. Thus, there is an urgent need for study of potential sea-ice indicators, particularly from the Paleogene when the Earth transitioned from a greenhouse to icehouse climate. Preliminary studies of Paleogene sediments from Integrated Ocean Drilling Program (IODP) Expedition 302, the Arctic Coring Expedition (ACEX), indicate that different archaeomonad assemblages characterize the sea-ice and ice-free intervals of these cores, suggesting that archaeomonads (cysts of marine alage) may be useful as a sea-ice proxy. Relatively little is known about the evolution and paleoecology of archaeomonds; therefore this project examines assemblages from the Arctic and Antarctic, spanning the Cretaceous to Neogene, to better understand the evolution and paleoecology of this group. The oldest known archaeomonads are Cretaceous in age, and therefore thought to have evolved during an ice-free interval of Earth history. These forms are compared to Eocene/Oligocene assemblages in the Arctic and Antarctic to identify species associated with the presence of sea ice. Selected Neogene cores are examined to relate archaeomonads to the continued evolution of Earth?s cryosphere. The findings are applied to the studied cores to reconstruct the paleoenvironment in polar regions at different times during the Cenozoic. Very little work has been done on extinct marine archaeomonads, even though their modern ecology makes them likely sea-ice proxies. This study examines the evolution and paleoecology of archaeomonads to identify forms for sea-ice reconstruction. The results will be particularly useful for understanding the time period when sea ice first formed in the Arctic through study of the ACEX cores. This knowledge is necessary to better understand the evolution of Earth?s cryosphere and how future warming will affect global climate. The identification of extinct organisms useful as sea-ice proxies will give paleoceanographers new methods to reconstruct time series of past sea-ice extent. This will further understanding of how Cenozoic global climate has evolved, and may impact global climate models for prediction of future climate.