DOI: 10.5281/zenodo.5784501
title: Improved Bathymetric Prediction using Geological Information: SYNBATH

description: Manuscript in revision: <em>Earth and Space Science, </em>December 20, 2021 <em>Abstract</em> To date, approximately 20% of the ocean floor has been surveyed by ships at a spatial resolution of 400 m or better. The remaining 80% has depth predicted from satellite altimeter-derived gravity measurements at a relatively low resolution. There are many remote ocean areas in the southern hemisphere that will not be completely mapped at 400 m resolution during this decade. This study is focused on the development of synthetic bathymetry to fill the gaps. There are two types of seafloor features that are not typically well resolved by satellite gravity: abyssal hills and small seamounts (&lt; 2.5 km tall). We generate synthetic realizations of abyssal hills by combining the measured statistical properties of mapped abyssal hills with regional geology including fossil spreading rate/orientation, rms height from satellite gravity, and sediment thickness. With recent improvements in accuracy and resolution, It is now possible to detect all seamounts taller than about 800 m in satellite-derived gravity and their location can be determined to an accuracy of better than 1 km. However, the width of the gravity anomaly is much greater than the actual width of the seamount so the seamount predicted from gravity will underestimate the true seamount height and overestimate its base dimension. In this study we use the amplitude of the vertical gravity gradient (VGG) to estimate the mass of the seamount and then use their characteristic shape, based on well surveyed seamounts, to replace the smooth predicted seamount with a seamount having a more realistic shape. SYNBATH_V1.2 September 20, 2021 This version of SYNBATH has abyssal hills as described below. Superimposed on that are 30,000 gaussian seamounts with sigma to height ratios of 2.4. The heights were determined by fitting a uncompensated model VGG for a seamount of a particular height to the observed VGG in a 33 by 33 km area using a density of 2800 kg m^-3. Any seamount taller than 2600 m or less than 700 m was not used. SYNBATH_V1.1 July 6, 2021 A refined version of the SYNBAPS with better blending SYNBATH_V1.0 July 1, 2021 This is the first version of SYNthetic BATHymetry (SYNBATH) that is a merge of the latest SRTM15 global bathymetry/topography grid and synthetic abyssal hill fabric based on an anisotropic power spectral model published by Goff and others [2010, 2020]. The synthetic abyssal fabric fills the voids in the real bathymetry coverage that used to be filled by predicted depth. These are global grids with 86400 columns and 43200 rows in NETCDF format. Seamount Heights used in SYNBATH_V1.2 December 15, 2021 This directory contains the locations and heights of the seamounts in the combined New and Kim Wessel (KW) catalogues. There are three categories of seamounts. 1) good.nxybh - contains 34295 with heights successfully modeled using the VGG as described in the Sandwell 2022 publication. The file has 5 columns: name longitude latitude base_depth height_VGG<br> KW-00001 0.191666666667 -6.44166666667 -4060.15673828 2600<br> KW-00002 -0.425 -6.84166666667 -4125.54345703 2600<br> KW-00003 -0.075 -6.875 -4221.48730469 2600<br> .<br> .<br> . <br> 2) uncharted.nxybh - contains 19732 seamounts that are more than 3 km from a depth sounding. The file has 5 columns: name longitude latitude base_depth height_VGG<br> New-00001 3.60833333333 2.74166666667 -3990.33374023 2000<br> New-00002 3.375 2.59166666667 -4113.46435547 1500<br> New-00003 3.19166666667 2.475 -4209.29638672 1200<br> .<br> .<br> . 3) well_charted.nxybh - contains 739 seamounts that are well charted by more than 50% sounding coverage over the seamount and good coverage at the summit so the summit depth is known. The file has 6 columns: name longitude latitude base_depth height_VGG summit_depth<br> New-00707 -8.525 71.4916666667 -2094.12524414 1000 -1044.107788<br> New-00786 -4.775 70.0083333333 -2978.39868164 1200 -2427.73095683<br> New-00808 -4.375 66.2583333333 -3378.35644531 1100 -2656.7897947<br> .<br> .<br> . In addition, there are three matching kmz-files so the locations of the seamounts can be viewed in Google Earth.<br> good.kmz - yellow dots<br> uncharted.kmz - red dots<br> well_charted.kmz - green dots
description: Acknowledgements - This work was supported by the Office of Naval Research (N00014-17-1-2866), NASA SWOT program (NNX16AH64G and 80NSSC20K1138) and the Nippon Foundation through the SeaBed2030 project. The Generic Mapping Tools (GMT) [Wessel et al., 2019] were extensively used in data processing. The views, opinions, and findings contained in the report are those of the authors and should not be construed as an official National Oceanic and Atmospheric Administration or U.S. Government position, policy, or decision.