GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 245-13
Presentation Time: 11:15 AM


MILLER, Kenneth G., BROWNING, James V., MOUNTAIN, Gregory S., SCHMELZ, W. John, KOPP, Robert E. and WRIGHT, James D., Department of Earth and Planetary Sciences, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854

Sea-level history reflects the Earth’s thermal and cryospheric evolution and the behavior and operation of the climate system under ice-free and glaciated conditions. IODP has provided constraints on the timing, magnitudes, and rates of sea-level change, with coring of: 1) carbonate platforms and atolls (Exp 310 Tahiti; Exp 325, Great Barrier Reef); 2) continental margins (Legs 150, 150X, 174A, 174AX, & Exp 313, New Jersey; Exp 317 New Zealand); and 3) deep sea sections that provide continuous δ18O and Mg/Ca proxy records for ice-volume changes. Comparisons between Cenozoic sea-level estimates from backstripping the mid-Atlantic U.S. with those from deep Pacific Ocean δ18O-Mg/Ca records show similar timings and amplitudes reflecting Global Mean Sea Level changes (GMSL). Peak warmth, peak sea levels, high CO2 (>1000 ppm), and ice-free conditions occurred in the Hothouse Early Eocene (55-48 Ma), with GMSL falls of ~15 m reflecting growth and decay of a small East Antarctic Ice Sheet (EAIS) or other mechanisms. Cool greenhouse (Paleocene, Middle to Late Eocene) sea-level changes of 15-25 m were caused by growth and decay of small (~1/3 of modern) EAIS ice sheets with ice-free interglacials. During the largely unipolar Icehouse of the Oligocene-Early Miocene, the EAIS was not permanently developed, with periods of large-scale growth and deglaciation associated with ~50 m sea-level fluctuations. During the Miocene Climate Optimum (MCO; ~17-15 Ma) ice-volume changes were small (<20 m), with ice-free conditions likely attained. Development of a permanent EAIS occurred as 3 steps during the Middle Miocene Climate Transition (MMCT; 14.8-12.8 Ma). During the Middle to Late Miocene the EAIS was relatively stable with ~20-30 m Myr-scale sea-level variations. During the Pliocene Climate Optimum (PCO, ca. 3-4 Ma), sea levels peaked at 12-20 m above present, requiring loss of ice in Greenland, West Antarctica, and portions of the EAIS, despite CO2 levels similar to 2019. Large lowerings (60-130 m) were restricted to the past 2.7 Myr, associated with continental-scale Northern Hemisphere ice sheets. The last glacial maximum stands as the largest sea-level lowering (~130 m) of the Mesozoic-Cenozoic. Rates of sea-level rise during the last deglaciation (ca. 20-10 ka) reached 40 mm/yr, the fastest GMSL rise yet measured in the Cenozoic record.