We review Phanerozoic sea-level changes [543 million years ago (Ma) to the present] on various time scales and present a new sea-level record for the past 100 million years (My). Long-term sea level peaked at 100 +/- 50 meters during the Cretaceous, implying that ocean-crust production rates were much lower than previously inferred. Sea level mirrors oxygen isotope variations, reflecting ice-volume change on the 10(4)- to 10(6)-year scale, but a link between oxygen isotope and sea level on the 10(7)-year scale must be due to temperature changes that we attribute to tectonically controlled carbon dioxide variations. Sea-level change has influenced phytoplankton evolution, ocean chemistry, and the loci of carbonate, organic carbon, and siliciclastic sediment burial. Over the past 100 My, sea-level changes reflect global climate evolution from a time of ephemeral Antarctic ice sheets (100 to 33 Ma), through a time of large ice sheets primarily in Antarctica (33 to 2.5 Ma), to a world with large Antarctic and large, variable Northern Hemisphere ice sheets (2.5 Ma to the present).

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[1] High-resolution stable carbon isotope records for upper Paleocene-lower Eocene sections at Ocean Drilling Program Sites 1051 and 690 and Deep Sea Drilling Project Sites 550 and 577 show numerous rapid (40-60 kyr duration) negative excursions of up to 1%. We demonstrate that these transient decreases are the expected result of nonlinear insolation forcing of the carbon cycle in the context of a long carbon residence time. The transients occur at maxima in Earth's orbital eccentricity, which result in high-amplitude variations in insolation due to forcing by climatic precession. The construction of accurate orbital chronologies for geologic sections older than $35 Ma relies on identifying a high-fidelity recorder of variations in Earth's orbital eccentricity. We use the carbon isotope records as such a recorder, establishing a robust orbitally tuned chronology for latest Paleoceneearliest Eocene events. Moreover, the transient decreases provide a means of precise correlation among the four sites that is independent of magnetostratigraphic and biostratigraphic data at the <10 5 -year scale. While the eccentricity-controlled transient decreases bear some resemblance to the much larger-amplitude carbon isotope excursion (CIE) that marks the Paleocene/Eocene boundary, the latter event is found to occur near a minimum in the $400-kyr eccentricity cycle. Thus the CIE occurred during a time of minimal variability in insolation, the dominant mechanism for forcing climate change on 10 4 -year scales. We argue that this is inconsistent with mechanisms that rely on a threshold climate event to trigger the Paleocene/Eocene thermal maximum since any threshold would more likely be crossed during a period of high-amplitude climate variations.

18 O bf , Mg/Ca bf , and sea level records as robust climate proxies. Our reconstructions indicate differences between deep ocean cooling and continental ice growth in the late Cenozoic: cooling occurred gradually in the middle-late Eocene and late Miocene-Pliocene while ice growth occurred rapidly in the earliest Oligocene, middle Miocene, and Plio-Pleistocene. These differences are consistent with climate models that imply that temperatures, set by the long-term CO 2 equilibrium, should change only gradually on timescales >2 Myr, but growth of continental ice sheets may be rapid in response to climate thresholds due to feedbacks that are not yet fully understood.

We obtained global sea-level (eustatic) estimates with a peak of ~22 m higher than present for the Pliocene interval 2.7-3.2 Ma from backstripping in Virginia (United States), New Zealand, and Enewetak Atoll (north Pacifi c Ocean), benthic foraminiferal δ 18 O values, and Mg/Ca-δ 18 O estimates. Statistical analysis indicates that it is likely (68% confi dence interval) that peak sea level was 22 ± 5 m higher than modern, and extremely likely (95%) that it was 22 ± 10 m higher than modern. Benthic foraminiferal δ 18 O values appear to require that the peak was <20-21 m. Our estimates imply loss of the equivalent of the Greenland and West Antarctic ice sheets, and some volume loss from the East Antarctic Ice Sheet, and address the longstanding controversy concerning the Pliocene stability of the East Antarctic Ice Sheet. INTRODUCTIONPliocene studies allow evaluation of relationships among global climate, atmospheric CO 2 , and sea-level changes under conditions significantly warmer than today, but with a similar paleogeographic confi guration (Raymo et al., 2009(Raymo et al., , 2011Rohling et al., 2009). Paleotemperature proxies indicate that average global surface temperatures ca. 3 Ma were 2-3 °C warmer than present (Dowsett, 2007). Atmospheric CO 2 estimates for the warm Pliocene are not well constrained (330-415 ppmv; e.g., Pagani et al., 2010), but appear comparable to 390 ppmv measured in 2011 (Common Era, CE) and higher than preanthropogenic levels (280 ppmv).Published estimates of the peak Pliocene sea level have a wide range, though a ~25 m peak is widely cited (e.g., Raymo et al., 2009;Rohling et al., 2009). A peak of 35 m was obtained by estimating uplift rates for the Orangeburg scarp in North and South Carolina (southeastern United States; +35 ± 18 m; Dowsett and Cronin, 1990); a similar estimate was obtained from uplifted deposits in Alaska (+40 m; Brigham-Grette and Carter, 1992) (Fig. 1). The ~25 m estimate for the highstand generally cited is based on Dowsett and Cronin (1990), as updated by Dowsett et al. (1999) to be consistent with a lesser ice inventory, and was not independently derived. Melting of all modern ice sheets would raise sea level by 64 ± 4 m, with 7 m from Greenland and 5 m from the West Antarctic Ice Sheet (WAIS) (Lythe et al., 2001). Thus, an estimate of a 25-35 m peak implies full deglaciation of Greenland and the WAIS, and signifi cant removal (~25%-45%) of the East Antarctic Ice Sheet (EAIS).Pliocene global sea-level changes have been reconstructed using records from atolls (Wardlaw and Quinn, 1991), benthic foraminiferal δ 18 O (Kennett and Hodell, 1995;Miller et al., 2005Miller et al., , 2011, Mg/Ca (Sosdian andRosenthal, 2009), and continental margins (Naish andWilson, 2009). Each method has its limitations. Sea-level changes recorded in coral atolls provide precise water-depth changes, but modeling subsidence rates and dating can be challenging. The δ 18 O method is complicated by separating deep water temperature from δ 18 O seawater changes due to ice volume variations....

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On the basis of a carbon isotopic record of both marine carbonates and organic matter from the Triassic-Jurassic boundary to the present, we modeled oxygen concentrations over the past 205 million years. Our analysis indicates that atmospheric oxygen approximately doubled over this period, with relatively rapid increases in the early Jurassic and the Eocene. We suggest that the overall increase in oxygen, mediated by the formation of passive continental margins along the Atlantic Ocean during the opening phase of the current Wilson cycle, was a critical factor in the evolution, radiation, and subsequent increase in average size of placental mammals.

Global cooling and the development of continental-scale Antarctic glaciation occurred in the late middle Eocene to early Oligocene (~38 to 28 million years ago), accompanied by deep-ocean reorganization attributed to gradual Antarctic Circumpolar Current (ACC) development. Our benthic foraminiferal stable isotope comparisons show that a large δ(13)C offset developed between mid-depth (~600 meters) and deep (>1000 meters) western North Atlantic waters in the early Oligocene, indicating the development of intermediate-depth δ(13)C and O(2) minima closely linked in the modern ocean to northward incursion of Antarctic Intermediate Water. At the same time, the ocean's coldest waters became restricted to south of the ACC, probably forming a bottom-ocean layer, as in the modern ocean. We show that the modern four-layer ocean structure (surface, intermediate, deep, and bottom waters) developed during the early Oligocene as a consequence of the ACC.