We present Bedmap2, a new suite of gridded products describing surface elevation, ice-thickness and the seafloor and subglacial bed elevation of the Antarctic south of 60° S. We derived these products using data from a variety of sources, including many substantial surveys completed since the original Bedmap compilation (Bedmap1) in 2001. In particular, the Bedmap2 ice thickness grid is made from 25 million measurements, over two orders of magnitude more than were used in Bedmap1. In most parts of Antarctica the subglacial landscape is visible in much greater detail than was previously available and the improved data-coverage has in many areas revealed the full scale of mountain ranges, valleys, basins and troughs, only fragments of which were previously indicated in local surveys. The derived statistics for Bedmap2 show that the volume of ice contained in the Antarctic ice sheet (27 million km³) and its potential contribution to sea-level rise (58 m) are similar to those of Bedmap1, but the mean thickness of the ice sheet is 4.6% greater, the mean depth of the bed beneath the grounded ice sheet is 72 m lower and the area of ice sheet grounded on bed below sea level is increased by 10%. The Bedmap2 compilation highlights several areas beneath the ice sheet where the bed elevation is substantially lower than the deepest bed indicated by Bedmap1. These products, along with grids of data coverage and uncertainty, provide new opportunities for detailed modelling of the past and future evolution of the Antarctic ice sheets

We present Bedmap2, a new suite of gridded products describing surface elevation, ice-thickness and the seafloor and subglacial bed elevation of the Antarctic south of 60° S. We derived these products using data from a variety of sources, including many substantial surveys completed since the original Bedmap compilation (Bedmap1) in 2001. In particular, the Bedmap2 ice thickness grid is made from 25 million measurements, over two orders of magnitude more than were used in Bedmap1. In most parts of Antarctica the subglacial landscape is visible in much greater detail than was previously available and the improved coverage of data has in many areas revealed the full scale of mountain ranges, valleys, basins and troughs, only fragments of which were previously indicated in local surveys. The derived statistics for Bedmap2 show that the volume of ice contained in the Antarctic ice sheet (27 million km³) and its potential contribution to sea-level rise (58 m) are similar to those of Bedmap1, but the mean thickness of the ice sheet is 4.6 % greater, the mean depth of the bed beneath the grounded ice sheet is 72 m lower and the area of ice sheet grounded on bed below sea level is increased by 10 %. The Bedmap2 compilation highlights several areas beneath the ice sheet where the bed elevation is substantially lower than the deepest bed indicated by Bedmap1. These products, along with grids of data coverage and uncertainty, provide new opportunities for detailed modelling of the past and future evolution of the Antarctic ice sheets

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Abstract. We used 50 kHz sonar data to estimate natural hydrocarbon emission rates from the 18 km 2 marine seep field offshore from Coal Oil Point, Santa Barbara, California. The hydrocarbon gas emission rate is 1.7 + 0.3 x 105 m3d -1 (including gas captured by a subsea seep containment device) and •he associated oil emission rate is 1.6 + 0.2 x 104 Ld -l (100 barrels d-l). The nonmethane hydrocarbon emission rate from the gas seepage is 35 + 7 td -1 and a large source of air pollution in Santa Barbara County. Our estimate is equal to twice the emission rate fi-om all the on-road vehicle traffic in the county.

Antarctic ice sheet (AIS) growth and decay is strongly influenced by astronomical variations, yet it is not known why AIS response to this climate driver varies through time. Here we examine AIS variability from 34 to 5 million years ago through integration of geological records from the Antarctic margin and a novel assessment of sensitivity to changes in Earth's axial tilt (obliquity sensitivity) derived from the oceanic oxygen-isotope proxy for global ice volume. Three phases of AIS development are found: (1) ~34-24 Ma-a largely terrestrial ice sheet with low obliquity sensitivity; (2) 24 to 14 Ma-frequent ephemeral marine ice sheets with amplified obliquity sensitivity; and (3) 14 to 5 Ma-episodes of extensive marine ice sheet advance, persistent sea ice, and a general decrease in obliquity sensitivity. These phases are associated with decreasing atmospheric CO2 and progressively colder mean climate states. Our analysis suggests the AIS is most sensitive to obliquity forcing when it extends into marine environments and sea-ice extent is limited. We infer this is due to obliquity-driven changes in meridional temperature gradient that affect the position and strength of circum-Antarctic easterly flow, which enhances (or reduces) ocean heat transport across the Antarctic continental margin. Insight into causes of Antarctic ice sheet variability-over a range of time scales-is fundamental to our understanding of Earth system response to climate change. Large scale shifts in AIS volume and extent are controlled by changes in atmospheric CO2 1,2 and plate

Hydrothermal vents jetting out water at 380 degrees +/- 30 degrees C have been discovered on the axis of the East Pacific Rise. The hottest waters issue from mineralized chimneys and are blackened by sulfide precipitates. These hydrothermal springs are the sites of actively forming massive sulfide mineral deposits. Cooler springs are clear to milky and support exotic benthic communities of giant tube worms, clams, and crabs similar to those found at the Galápagos spreading center. Four prototype geophysical experiments were successfully conducted in and near the vent area: seismic refraction measurements with both source (thumper) and receivers on the sea floor, on-bottom gravity measurements, in situ magnetic gradiometer measurements from the submersible Alvin over a sea-floor magnetic reversal boundary, and an active electrical sounding experiment. These high-resolution determinations of crustal properties along the spreading center were made to gain knowledge of the source of new oceanic crust and marine magnetic anomalies, the nature of the axial magma chamber, and the depth of hydrothermal circulation.

Reconstructions of Antarctic paleotopography for the late Eocene suggest that glacial erosion and thermal subsidence have lowered West Antarctic elevations considerably since then, with Antarctic land area having decreased ~20%. A new climate‐ice sheet model based on these reconstructions shows that the West Antarctic Ice Sheet first formed at the Eocene‐Oligocene transition (33.8–33.5 Ma, E‐O) in concert with the continental‐scale expansion of the East Antarctica Ice Sheet and that the total volume of East and West Antarctic ice (33.4–35.9 × 106 km3) was >1.4 times greater than previously assumed. This larger modeled ice volume is consistent with a modest cooling of 1–2°C in the deep ocean during the E‐O transition, lower than other estimates of ~3°C cooling, and suggests the possibility of substantial ice in the Antarctic interior before the Eocene‐Oligocene boundary.