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It has been proposed that during Pleistocene glaciations, an ice cap of 1 kilometre or greater thickness covered the Arctic Ocean 1 , 2 , 3 . This notion contrasts with the prevailing view that the Arctic Ocean was covered only by perennial sea ice with scattered icebergs 4 , 5 , 6 . Detailed mapping of the ocean floor is the best means to resolve this issue. Although sea-floor imagery has been used to reconstruct the glacial history of the Antarctic shelf  7 , 8 , 9 , little data have been collected in the Arctic Ocean because of operational constraints 10 , 11 . The use of a geophysical mapping system during the submarine SCICEX expedition in 1999 12 provided the opportunity to perform such an investigation over a large portion of the Arctic Ocean. Here we analyse backscatter images and sub-bottom profiler records obtained during this expedition from depths as great as 1 kilometre. These records show multiple bedforms indicative of glacial scouring and moulding of sea floor, combined with large-scale erosion of submarine ridge crests. These distinct glaciogenic features demonstrate that immense, Antarctic-type ice shelves up to 1 kilometre thick and hundreds of kilometres long existed in the Arctic Ocean during Pleistocene glaciations.

Heat transported from the mantle beneath spreading centers creates an astonishingly narrow ribbon of convective heat discharge at plate boundaries, as apparently demonstrated by exhaustive exploration for hydrothermal discharge sites over the last three decades. Recent observations and models are now challenging this assumption of exclusively axis‐centric high‐temperature venting. One example is the proposal that intense cooling along the vertical boundaries of a broad low‐velocity volume (LVV) of hot crust could generate high‐temperature fluids several kilometers off axis. To test the hypothesis that substantial hydrothermal discharge might occur beyond the LVV, we conducted a dense survey grid of the ridge and surrounding seafloor (up to ±5 km) along 175 km of the Eastern Lau Spreading Center and Valu Fa Ridge (∼1800 km of track line). Our sampling array extended from ∼50 to 400 m above bottom and included light‐scattering, oxidation‐reduction potential, and hydrographic sensors attached to the tow line and beneath the IMI120 sonar mapping system. The surveys successfully mapped plumes from several vent fields in the neovolcanic zone (∼±1.5 km about the axis) but did not detect evidence of significant discharge anywhere farther off‐axis. At a few locations on the Valu Fa Ridge, however, we did record oxidation‐reduction potential anomalies with hydrographic density signatures that imply low‐temperature hydrothermal sources on the axial flank. Although these sites are hundreds of meters deeper than the adjacent crest, they are above, not beyond, the previously mapped LVV. Our results thus do not support a simple picture of high‐temperature fluids ascending undiluted through the crust to the seafloor several kilometers off‐axis. However, we cannot exclude the possibilities that the largely unmapped LVV is narrower here than seen on other ridges, that hydrothermal fluids formed beyond the LVV are channeled to the axis, or that discharge beyond the neovolcanic zone occurs only as dispersed, very low‐temperature fluids. Our observations do demonstrate that high‐temperature discharge predominantly exits the seafloor within a narrow (∼±1.5 km) axial ribbon, regardless of the presence or absence of an axial magma chamber.

During the summer of 2012, the new research vessel (R/V) Sikuliaq, a 261-foot-long ( similar to 80 m) ship capable of working in and around first-year sea ice in polar regions, will be launched. The vessel is scheduled to commence science operations in early 2014 after extensive testing and field trials in the later half of 2013. Sikuliaq, pronounced [see-KOO-lee-auk], is an Inupiat name meaning \"young sea ice,\" an indication of the important role the ship is meant to play in helping scientists understand and monitor changes in ice-covered waters. R/V Sikuliaq represents a unique addition to the US academic fleet, having an ice-strengthened hull designed to break through first-year ice up to 2.5-feet (.76 m) thick at speeds of a few knots. Although the ship was designed to facilitate studies of environmental change in the Arctic and subarctic, its size and general scientific capabilities make it well suited to conduct research throughout the global ocean.

Lava erupts into cold sea water on the ocean floor at mid-ocean ridges (at depths of 2,500 m and greater), and the resulting flows make up the upper part of the global oceanic crust 1 . Interactions between heated sea water and molten basaltic lava could exert significant control on the dynamics of lava flows and on their chemistry. But it has been thought that heating sea water at pressures of several hundred bars cannot produce significant amounts of vapour 2 , 3 , 4 , 5 and that a thick crust of chilled glass on the exterior of lava flows minimizes the interaction of lava with sea water. Here we present evidence to the contrary, and show that bubbles of vaporized sea water often rise through the base of lava flows and collect beneath the chilled upper crust. These bubbles of steam at magmatic temperatures may interact both chemically and physically with flowing lava, which could influence our understanding of deep-sea volcanic processes and oceanic crustal construction more generally 6 . We infer that vapour formation plays an important role in creating the collapse features that characterize much of the upper oceanic crust and may accordingly contribute to the measured low seismic velocities in this layer.

The International Bathymetric Chart of the Arctic Ocean (IBCAO) released its first gridded bathymetric compilation in 1999. The IBCAO bathymetric portrayals have since supported a wide range of Arctic science activities, for example, by providing constraint for ocean circulation models and the means to define and formulate hypotheses about the geologic origin of Arctic undersea features. IBCAO Version 3.0 represents the largest improvement since 1999 taking advantage of new data sets collected by the circum‐Arctic nations, opportunistic data collected from fishing vessels, data acquired from US Navy submarines and from research ships of various nations. Built using an improved gridding algorithm, this new grid is on a 500 meter spacing, revealing much greater details of the Arctic seafloor than IBCAO Version 1.0 (2.5 km) and Version 2.0 (2.0 km). The area covered by multibeam surveys has increased from ∼6% in Version 2.0 to ∼11% in Version 3.0. Key Points New gridded bathymetric portrayal of the Arctic Ocean Bathymetric crowd source data shows a new potential for the mapping community

Deep sea photographs were collected for several camera-tow transects along and across the axis at the East Pacific Rise crest between 9°49' and 9°52' N, covering terrain out to 2 km from the ridge axis. The objective of the surveys was to utilize fine-scale morphology and imagery of seafloor volcanic terrain to aid in interpreting eruptive history and lava emplacement processes along this fast-spreading mid-ocean ridge. The area surveyed corresponds to the region over which seismic layer 2A, believed to correspond to the extrusive oceanic layer, attains full thickness (Christeson et al., 1994a, b, 1996; Hooft et al., 1996; Carbotte et al., 1997). The photographic data are used to identify the different eruptive styles occurring along the ridge crest, map the distribution of the different morphologies, constrain the relative proportions of the three main morphologies and discuss the implications of these results. Morphologic distributions of lava for the area investigated are 66% lobate lava, 20% sheet lava, 10% pillow lava, and 4% transitional morphologies between the other three main types. There are variations in inferred relative lava ages among the different morphological types that do not conform to a simple increase in age versus distance relationship from the spreading axis, suggesting a model in which off-axis transport and volcanism contribute to the accumulation of the extrusive layer. Analysis of the data suggests this ridge crest has experienced three distinctly different types of volcanic emplacement processes: (1) axial summit eruptions within a 1 km wide zone centered on the axial summit collapse trough (ASCT); (2) off-axis transport of lava erupted at or near the ASCT through channelized surface flows; and (3) off-axis eruptions and local constructional volcanism at distances of 0.5-1.5 km from the axis. Major element analyses of basaltic glasses from lavas collected by Alvin, rock corer and dredging in this area indicate that the most recent magmatic event associated with the present ASCT erupted relatively homogeneous and mafic (>8.25 weight percent wt.% MgO) basalts compared to older, off-axis lavas which tend to be more chemically evolved (Perfit and Chadwick, 1998; Perfit and Fornari, unpublished data). The more primitive lavas have a more extensive distribution within and east of the ASCT. More evolved basalts (MgO <8.0wt.%) are concentrated in a broad area a few kilometers east of the axis, and in an oval-shaped area south of 9°50' N, west of the ASCT. Transitional and enriched (T- and E-) mid-ocean ridge basalts exist in relatively small areas (<1 km^sup 2^) on the crestal plateau and correlate with scarps or fissures where pillow lavas were erupted. Mafic lavas in this area are primarily related to the youngest magmatic events. Geochemical analysis of samples collected at distances >500 m from the ASCT suggests that regions of off-axis volcanism may be sourced from older and cooler sections of the axial magma lens. Analysis of these data suggests that this portion of the EPR has not experienced large scale volcanic overprinting in the past 30 ka. The predominance of lobate flows (66%) throughout much of the crestal region, and subtle variations in sediment cover and apparent age between flows, suggest that eruptive volumes and effusion rates of individual eruptions have been similar over much of the last 30 ka and that most of the eruptions have been small, probably similar in volume to the 1991 EPR flow which had an estimated volume of 1×10^sup 6^ m^sup 3^ (Gregg et al., 1996).[PUBLICATION ABSTRACT]

Edwards and Carniel discuss military munitions in the sea. Discarded military munitions and unexploded ordnance are lingering reminders of historic conflicts and may pose a large problem when encountered in the world's oceans today. They may contain conventional explosives or chemical agents and thus may present a threat to people or to the environment. In 2007, the US Department of Defense (DOD) established a program to investigate munitions in the region south of Pearl Harbor, Oahu, Hawaii. The project, entitled the Hawaii Undersea Military Munitions Assessment, focused on DOD sea disposal site HI-05, an area characterized by water depths of 300 to 700 m. The boundaries of the HI-05 sea disposal site were only generally defined, extending from Barber's Point on the western side of Oahu to Diamond Head crater on the eastern side, and from Pearl Harbor to the south.

Deep sea photographs were collected for several camera-tow transects along and across the axis at the East Pacific Rise crest between 949' and 952'N, covering terrain out to 2km from the ridge axis. The objective of the surveys was to utilize fine-scale morphology and imagery of seafloor volcanic terrain to aid in interpreting eruptive history and lava emplacement processes along this fast-spreading mid-ocean ridge. The area surveyed corresponds to the region over which seismic layer 2A, believed to correspond to the extrusive oceanic layer, attains full thickness (Christeson etal., 1994, b, 1996; Hooft etal., 1996; Carbotte etal., 1997). The photographic data are used to identify the different eruptive styles occurring along the ridge crest, map the distribution of the different morphologies, constrain the relative proportions of the three main morphologies and discuss the implications of these results. Morphologic distributions of lava for the area investigated are 66% lobate lava, 20% sheet lava, 10% pillow lava, and 4% transitional morphologies between the other three main types. There are variations in inferred relative lava ages among the different morphological types that do not conform to a simple increase in age versus distance relationship from the spreading axis, suggesting a model in which off-axis transport and volcanism contribute to the accumulation of the extrusive layer. Analysis of the data suggests this ridge crest has experienced three distinctly different types of volcanic emplacement processes: (1) axial summit eruptions within a 1km wide zone centered on the axial summit collapse trough (ASCT); (2) off-axis transport of lava erupted at or near the ASCT through channelized surface flows; and (3) off-axis eruptions and local constructional volcanism at distances of 0.5-1.5km from the axis. Major element analyses of basaltic glasses from lavas collected by Alvin, rock corer and dredging in this area indicate that the most recent magmatic event associated with the present ASCT erupted relatively homogeneous and mafic (>8.25 weight percent wt.% MgO) basalts compared to older, off-axis lavas which tend to be more chemically evolved (Perfit and Chadwick, 1998; Perfit and Fornari, unpublished data). The more primitive lavas have a more extensive distribution within and east of the ASCT. More evolved basalts (MgO <8.0wt.%) are concentrated in a broad area a few kilometers east of the axis, and in an oval-shaped area south of 950'N, west of the ASCT. Transitional and enriched (T- and E-) mid-ocean ridge basalts exist in relatively small areas (<1km super(2)) on the crestal plateau and correlate with scarps or fissures where pillow lavas were erupted. Mafic lavas in this area are primarily related to the youngest magmatic events. Geochemical analysis of samples collected at distances >500m from the ASCT suggests that regions of off-axis volcanism may be sourced from older and cooler sections of the axial magma lens. Analysis of these data suggests that this portion of the EPR has not experienced large scale volcanic overprinting in the past 30ka. The predominance of lobate flows (66%) throughout much of the crestal region, and subtle variations in sediment cover and apparent age between flows, suggest that eruptive volumes and effusion rates of individual eruptions have been similar over much of the last 30ka and that most of the eruptions have been small, probably similar in volume to the 1991 EPR flow which had an estimated volume of 110 super(6)m super(3) (Gregg etal., 1996).