IBCAO v. 4 (International Bathymetric Chart of the Arctic Ocean version 4)

The International Bathymetric Chart of the Arctic Ocean (IBCAO) project was initiated in 1997 to meet the need for up-to-date digital portrayals of the Arctic Ocean seafloor. The original international effort assembled all available Arctic bathymetric data and gridded them using a continuous curvature spline under tension at a resolution of 2.5 x 2.5 km to produce a Digital Bathymetric Model (DBM). The resulting DBM, compiled on a Polar Stereographic Projection, was unprecedented in its ability to depict the complexities of Arctic bathymetry and has provided the geospatial context for countless scientific studies. Since the initial IBCAO DBM (Ver. 1.0), two more versions have been published. Ver. 2.0, at 2 x 2 km resolution and Ver. 3 with 500 x 500 m resolution. In all cases, many data sources including multi- and single-beam bathymetry as well as contours and soundings digitized from depth charts were incorporated following the concept developed for IBCAO Ver. 1, where direct depth observations get the highest priority and digitized contours the lowest. Recently the IBCAO project has merged its efforts with the Nippon Foundation-GEBCO-Seabed 2030 Project, an international effort whose goal it is to see the entire world ocean mapped by 2030. Working under the auspices of the Seabed 2030 program (but maintaining the its well-recognized identity) we now introduce IBCAO Ver. 4.0, compiled using a refined gridding algorithm compared to previous versions and with nearly three times more area of the Arctic Ocean constrained by bathymetric data relative to Ver. 3.0. In preparation for the eventual production of a multi-resolution grid that changes resolution with water depth to reflect achievable resolution from surface vessels, Ver. 4 is being released at 200×200 m grid spacing. The compilation procedure of the bathymetric source data considers its native resolution. This results in a degree of oversampling where the native resolution does not justify a 200 m grid, but in those regions where this resolution is achievable (e.g. depths less than say 1500-2000 m) the higher resolution allows analyses and regional uses that previously were not possible, including the depiction of megascale glacial lineations, large pock-marks and the dynamics of newly discovered Arctic submarine channels.