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1] 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.

[1] The International Bathymetric Chart of the Southern Ocean (IBCSO) Version 1.0 is a new digital bathymetric model (DBM) portraying the seafloor of the circum-Antarctic waters south of 60 S. IBCSO is a regional mapping project of the General Bathymetric Chart of the Oceans (GEBCO). The IBCSO Version 1.0 DBM has been compiled from all available bathymetric data collectively gathered by more than 30 institutions from 15 countries. These data include multibeam and single-beam echo soundings, digitized depths from nautical charts, regional bathymetric gridded compilations, and predicted bathymetry. Specific gridding techniques were applied to compile the DBM from the bathymetric data of different origin, spatial distribution, resolution, and quality. The IBCSO Version 1.0 DBM has a resolution of 500 Â 500 m, based on a polar stereographic projection, and is publicly available together with a digital chart for printing from the project website (www.ibcso.org) and at http://dx

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The depositional history of the Storfjorden and Kveithola trough-mouth fans (TMFs) in the northwestern Barents\ud Sea has been investigatedwithin two coordinated Spanish and Italian projects in the framework of the International\ud Polar Year (IPY) Activity 367, NICE STREAMS. The investigation has been conducted using a multidisciplinary approach\ud to the study of sediment cores positioned on high-resolution multibeam bathymetry and TOPAS/CHIRP\ud sub-bottom profiles.\ud Core correlation and the age model were based on 27AMS 14C samples, rock magnetic parameters, lithofacies sequences,\ud and the presence of marker beds including two oxidized layers marking the post Last GlacialMaximum\ud (LGM) inception of deglaciation (OX-2) and the Younger Dryas cold climatic event (OX-1).\ud Sediment facies analysis allowed the distinction of a number of depositional processes whose onset appears\ud closely related to ice stream dynamics and oceanographic patterns in response to climate change. The glacigenic\ud diamictonwith lowwater content, high density, and high shear strength, deposited during glacial maxima, indicates\ud ice streams grounded at the shelf edge. Massive release of IRD occurred at the inception of deglaciation in\ud response to increased calving rates with possible outer ice streams lift off and collapse. The presence of a severalmeter-\ud thick sequence of interlaminated sediments deposited by subglacial outbursts of turbid meltwater\ud (plumites) indicates rapid ice streams' melting and retreat. Crudely-layered and heavily-bioturbated sediments\ud were deposited by contour currents under climatic/environmental conditions favorable to bioproductivity.\ud The extreme sedimentation rate of 3.4 cm a−1 calculated for the plumites from the upper-slope area indicates a\ud massive, nearly instantaneous (less than 150 years), terrigenous input corresponding to an outstanding meltwater\ud event.Wepropose these interlaminated sediments to represent the high-latitudemarine record ofMeltWater\ud Pulse 1a (MWP-1a). Different bathymetric and oceanographic conditions controlled locally the mode of glacial\ud retreat, resulting in different thickness of plumites on the upper continental slope of the Storfjorden and\ud Kveithola TMFs. It is possible that the southern part of Storfjorden TMF received additional sediments from the\ud deglaciation of the neighboring Kveithola ice stream

Bathymetry (seafloor depth), is a critical parameter providing the geospatial context for a multitude of marine scientific studies. Since 1997, the International Bathymetric Chart of the Arctic Ocean (IBCAO) has been the authoritative source of bathymetry for the Arctic Ocean. IBCAO has merged its efforts with the Nippon Foundation-GEBCO-Seabed 2030 Project, with the goal of mapping all of the oceans by 2030. Here we present the latest version (IBCAO Ver. 4.0), with more than twice the resolution (200 × 200 m versus 500 × 500 m) and with individual depth soundings constraining three times more area of the Arctic Ocean (∼19.8% versus 6.7%), than the previous IBCAO Ver. 3.0 released in 2012. Modern multibeam bathymetry comprises ∼14.3% in Ver. 4.0 compared to ∼5.4% in Ver. 3.0. Thus, the new IBCAO Ver. 4.0 has substantially more seafloor morphological information that offers new insights into a range of submarine features and processes; for example, the improved portrayal of Greenland fjords better serves predictive modelling of the fate of the Greenland Ice Sheet. Background & Summary A broad range of Arctic climate and environmental research, including questions on the declining cryosphere and the geological history of the Arctic Basin, require knowledge of the depth and shape of the seafloor 1-3. Bathymetry provides the geospatial framework for these and other studies 4 and has impact on many processes, including the pathways of ocean currents and, thus, the distribution of heat 5,6 , sea-ice decline 7 , the effect of inflowing warm waters on tidewater glaciers 8 , and the stability of marine-based ice streams and outlet glaciers grounded on the seabed 9-11. Bathymetric data from large parts of the Arctic Ocean are, however, not available or extremely sparse due to difficulties, both logistical and political, in accessing the region 12. The International Bathymetric Chart of the Arctic Ocean (IBCAO) project, was initiated in 1997 in St Petersburg, Russia, to address the need for up-to-date digital portrayals of the Arctic Ocean seafloor 13. Since 1997, three Digital Bathymetric Models (DBMs) have ingested new data sets compiled by the IBCAO project team and have been released for public use 14-16. These DBMs comprised grids with a regular cell size of 2.5 × 2.5 km (Ver. 1.0), 2 × 2 km (Ver. 2.0) and 500 × 500 m (Ver. 3.0) on a Polar Stereographic projection. Depth estimates for grid cells between constraining depth observations were interpolated by the continuous curvature spline in a tension gridding algorithm 17. All depth data available at the time of the compilations were used, including multi-and single-beam bathymetry, and contours and soundings digitized from depth charts, with direct depth observations having the highest priority and digitized contours the lowest 18. Recognizing the importance of complete global bathymetry, the General Bathymetric Chart of the Ocean (GEBCO), a project under the auspices of the International Hydrographic Organization (IHO) and the Intergovernmental Oceanographic Commissio...

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