An Overview of Climate & Sea-level Changes Over the Past 100 Million Years

Sea-level history reflects the thermal and cryospheric evolution of the Earth, providing a history of ice- sheet behavior and operation of the climate systems under ice-free and glaciated conditions. I compare ice-volume and sea-level estimates obtained from deep Pacific δ18O and Mg/Ca records with those from the mid-Atlantic U.S. obtained by “backstripping”, progressively accounting for the effects of compaction, loading, and thermal subsidence. Peak warmth, sea levels, high CO2 (\u3e1000 ppm), and mostly ice-free condition occurred in the Hothouse Late Cretaceous (ca. 100-66 Ma) and Early Eocene (55-47.9 Ma). During the cool greenhouse (Paleocene, Middle-Late Eocene) sea level was driven by ice growth and decay of small ice sheets. The Earth became a unipolar Icehouse world in the Oligocene-Pliocene (35-2.55 Ma) punctuated by the ice-free Miocene Climate Optimum (~17-15 Ma) and warmth of the Pliocene Climate Optimum, with partial loss of the East Antarctic ice sheet. Very large sea-level changes (60-130 m) were restricted to the past 2.7 Myr northern hemisphere “ice ages”. Following the last glacial sea-level lowering (~130 m), rates of sea-level exceeded 50 mm/yr, slowing to a Common Era “stillstand”, 20th century rise of 1-2 mm/yr, and a modern rise of 3 mm/yr. Projected sea-level rise in the 21st century is ~1 m under high emissions scenarios, with possible upper limit of over 2 m and rates exceeding 10 mm/yr