Ginger Barth Wayne E. Baldwin Robert S. Reece Sean S. Gulick William W. Danforth Florence L. Wong 20220825 raster digital data data release DOI: 10.5066/F7HM56HK Pacific Coastal and Marine Science Center, Santa Cruz, California U.S. Geological Survey https://doi.org/10.5066/F7HM56HK https://www.sciencebase.gov/catalog/item/560efc6ce4b0ba4884c5ed32 Ginger Barth Wayne E. Baldwin Robert S. Reece Sean S. Gulick William W. Danforth Florence L. Wong 2022 data release DOI: 10.5066/F7HM56HK Pacific Coastal and Marine Science Center, Santa Cruz, California U.S. Geological Survey https://doi.org/10.5066/F7HM56HK This raster dataset represents approximately 69,060 square kilometers of Simrad EM122 multibeam-backscatter data collected in the Gulf of Alaska during U.S. Geological Survey (USGS) cruise MGL1109 aboard the R/V Marcus G. Langseth. The data have been reduced for position, elevation, orientation, water-column sound-speed, and refraction effects. In June 2011, the U.S. Geological Survey (USGS) conducted a research cruise in the Gulf of Alaska aboard the R/V Marcus G. Langseth (Lamont-Doherty Earth Observatory, Columbia University) as part of the U.S. Extended Continental Shelf Project. The mission focused primarily on obtaining geophysical data (multichannel and CHIRP seismic reflection, ocean bottom seismometry, multibeam bathymetry, sonobuoy, XBT and XCTD) for the purposes of determining geologic framework, crustal nature, and sediment thickness in support of delineating the U.S. Extended Continental Shelf under provisions contained in Article 76 of the United Nations Convention on the Law of the Sea (UNCLOS). Additional information about the USGS field activities from which these data were derived is available online at: https://cmgds.marine.usgs.gov/fan_info.php?fan=L0911GA https://cmgds.marine.usgs.gov/fan_info.php?fan=2011-034-FA Additional information about the Lamont-Doherty field activities from which these data were derived is available online at: https://www.rvdata.us/search/cruise/MGL1108 https://www.rvdata.us/search/cruise/MGL1109 Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this Federal Geographic Data Committee-compliant metadata file is intended to document the data set in nonproprietary form, as well as in Esri format, this metadata file may include some Esri-specific terminology. 20110603 20110625 ground condition Complete None planned -152.381751 -137.797038 57.713119 48.268275 ISO 19115 Topic Category environment geoscientificInformation oceans Data Categories for Marine Planning Substrate Physical Habitats and Geomorphology USGS Thesaurus sea-floor characteristics multibeam sonar marine geophysics sea-floor acoustic reflectivity image mosaics geospatial datasets Marine Realms Information Bank (MRIB) keywords marine geophysics seismic methods multibeam echo sounder continental shelf None U.S. Geological Survey USGS Coastal and Marine Hazards and Resources Program CMHRP Pacific Coastal and Marine Science Center PCMSC backscatter intensity USGS Metadata Identifier USGS:560efc6ce4b0ba4884c5ed32 Geographic Names Information System (GNIS) Gulf of Alaska Bering Sea Kodiak Island Dutch Harbor NGA GEOnet Names Server (GNS) Baranof Fan Shirshov Ridge Kodiak Seamount Bowie Seamount Aleutian Trench Umnak Plateau Aleutian Basin Bowers Ridge None Surveyor Fan Extended Continental Shelf None USGS-authored or produced data and information are in the public domain from the U.S. Government and are freely redistributable with proper metadata and source attribution. Please recognize and acknowledge the U.S. Geological Survey as the originator of the dataset and in products derived from these data. This information is not intended for navigation purposes. U.S. Geological Survey, Pacific Coastal and Marine Science Center PCMSC Science Data Coordinator mailing and physical

2885 Mission Street

Santa Cruz CA 95060 831-427-4747 pcmsc_data@usgs.gov https://www.sciencebase.gov/catalog/file/get/560efc6ce4b0ba4884c5ed32?name=MGL1109backscat.jpg&allowOpen=true MGL1109 acoustic backscatter, Gulf of Alaska JPEG Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 3; ESRI ArcCatalog 9.3.1.1850 David W. Caress Dale N. Chayes 2006 https://www3.mbari.org/data/mbsystem/html/mbsystem_home.html Kongsberg-Simrad EM122 Multibeam Echosounder was used with transmit (fore-aft) and receive (athwart ships) beam widths of 1 degree, with swaths of 3-4 times water depth in water depths between 50 and 6000 m. Depth accuracies not determined, however Kongsberg-Simrad state that the system is capable of depth accuracies approaching 0.2 percent of water depth. No formal logical accuracy tests were conducted Raw EM122 Multibeam Echosounder data collected during OBS operations were not used in the generation of this gridded dataset because OBS instruments were deployed along transects coincident with previously surveyed ship track. Upon inspection in CARIS during post-processing it was deemed appropriate to exclude the redundant data from the gridding process. Horizontal positioning of the vessel was determined using a Kongsberg Seapath 300 series integrated inertial motion and positioning system. Positioning is accurate to better than 5 meters (at 95 percent confidence) during all surveying. All positioning is referenced to the WGS84 Datum. No attempt was made to determine the accuracy of the system although recorded depths are typically within +/-10 m of the center-beam multibeam sounding. Multibeam bathymetry and backscatter data were collected using a 12 kHz Kongsberg Simrad EM-122 multibeam echosounder and SIS (v3.8.2) acquisition software. The system consists of two hull-mounted transducer arrays, a transmit unit (150 deg. x 1 deg.) located along the ship centerline, and a receive unit (1 deg. x 30 deg.) that is abaft and oriented athwart-ships. The transducer pod is tilted 4 degrees towards the bow to reduce noise from cavitation and bubbles. The system forms a swath of 288 beams that produce an across-track profile of 432 soundings. The SIS software processes range/angle data from each ping during acquisition, merging position, inertial-motion, and sound-velocity data to derive a solution for vessel motion and raybending, and calculate sounding depths and positions. Sound velocity information entered into SIS was obtained from the Applied Micro Systems Micro SV mounted on the transducer pod and 52 XBT profiles. XBT profiles were extended to 12 km depth with data generated by the unix program 'mblevitus', a module of the multibeam processing package MB-System (Caress and Chayes, 2006). Average water column salinity of 34.4 ppt was determined by extrapolating data from XCDT casts. Multibeam data were collected nearly continuously throughout the cruise, effectively mapping the seafloor along the course of the ship's track. Beam angle was set at 70 on each side throughout the program and swath widths were generally between 3 and 4 times water depth. SIS logged bathymetry and backscatter solutions to the Simrad '.all' format for archival purposes. 201106 EM122 backscatter was processed and mosaicked using the FMGeocoder module in IVS Fledermaus. The Automatic Processing option (Mosaic only) was utilized with the EM122 Beam Time Series (from *.all raw files) selected as the backscatter source. A single tile mosaic, with 100 m per pixel resolution, was created for the entire survey area. The final mosaic was exported to these file formats: Fledermaus SD, GeoTIFF, ESRI ASCII Raster, and XYB format (Easting, Northing, dB value). The following project setup and processing parameters were specified: Project Coordinate System: Horiz. CS: WGS84,UTM,Zone 6N Custom Survey Area: XMIN,YMIN,XMAX,YMAX = 169100, 5385700, 1181500, 6408000 EM122 Sensor Config: Tx1:Xoff,Yoff,Zoff,Roff,Poff,Yoff = 20.92,0.57,8.46,0.16,-0.08,359.99 Tx2:Xoff,Yoff,Zoff,Roff,Poff,Yoff = 16.07,0.05,8.53,0.16,-0.08,0 IMU:Xoff,Yoff,Zoff,Roff,Poff,Yoff,lat = 0,0,0,-0.51,-0.23,0.43,0 Line Processing Parameters: Backscatter: Apply Beam Pattern Correction Beam Angle Cutoffs: start,cut = 0, 90 Backscatter Range: Calibrated,Min,Max = -70,10 AVG: Apply AVG - Flat Algorithm - Window Size 30 Statistics: Log space (dB) Navigation: Linear Interp. Format: Kongsberg(.all) Navigation Src.: Use Default Dual Swath Comp.: First O Sonar Defaults: Default Vals - Custom Override All - Sonar Type: Simrad EM122 MBES PrimFrq,SecFrq,MAN,MNB,ATBW,CTBW,SSS = 12000,0,120,484,2,4,1500 PusleL,PSR,SSR,Spread,TxPwr,RecGain,Abs = 5000,1001,0,0,1,1,30 Mosaicking Parameters: Line Blending = 50 percent Style, FiltType = Blend,dB Mean 201208 U.S. Geological Survey Wayne E. Baldwin Geologist mailing and physical address

384 Woods Hole Road

Woods Hole MA 02543-1598 USA 508-457-2226 wbaldwin@usgs.gov The output ESRI ASCII Raster file was imported as a floating point grid into ArcGIS 9.3 using the ASCII to Raster tool selected from the Conversion Tools - To Raster toolbox. 201208 U.S. Geological Survey Wayne E. Baldwin Geologist mailing and physical address

384 Woods Hole Road

Woods Hole MA 02543-1598 USA 508-457-2226 wbaldwin@usgs.gov Wrote version 1 of metadata. 20121018 U.S. Geological Survey Wayne E. Baldwin Geologist mailing and physical address

384 Woods Hole Road

Woods Hole MA 02543-1598 USA 508-457-2226 wbaldwin@usgs.gov Metadata was modified to bring up to current USGS PCMSC standards. Point of Contact and Metadata Contact information was updated. Keywords were added and refined. Cross Reference citation added. Details about different Network Resource Name links was given in the Access Instructions section. Minor typos were corrected. No data information was changed. 20220817 Susan A Cochran U.S. Geological Survey, Pacific Coastal and Marine Science Center Geologist mailing and physical

2885 Mission St.

Santa Cruz CA 95060 United States 831-460-7545 scochran@usgs.gov Raster Grid Cell 10224 10125 1 Universal Transverse Mercator 6 0.999600 -147.000000 0.000000 500000.000000 0.000000 row and column 100 100 meters D_WGS_84 WGS_84 6378137.0 298.257223563 Attribute Table Table containing attribute information associated with the data set. Producer defined Value backscatter intensity Producer defined -59.610 7.790 decibel > > Cell Size = 100 m > Data Type: Floating Point > Number of Rows = 10224 > Number of Columns = 10125 > > BOUNDARY (UTM Zone 6 meters) > > Xmin = 169050 > Xmax = 1181550 > Ymin = 5385650 > Ymax = 6408050 > > BOUNDARY (WGS84, excluding NODATA): > Xmin = -152.382 > Xmax = -137.797 > Ymin = 48.268 > Ymax = 57.713 > > BOUNDARY (converted from UTM zone 6 coordinates) > Xmin = -152.555 > Xmax = -135.657 > Ymin = 48.256 > Ymax = 57.815 > > STATISTICS (decibels) > > Minimum Value = -59.610 > Maximum Value = 7.790 > Mean = -27.752 > Standard Deviation = 2.751 > > COORDINATE SYSTEM DESCRIPTION > > Projection UTM > Zone 6 > Datum WGS84 > Units METERS > Spheroid WGS84 > The entity and attribute information was generated by the individual and/or agency identified as the originator of the data set. Please review the rest of the metadata record for additional details and information. U.S. Geological Survey - ScienceBase mailing and physical

Denver Federal Center, Building 810, Mail Stop 302

Denver CO 80225 1-888-275-8747 sciencebase@usgs.gov These data are available in ASCII GRID format, along with CSDGM FGDC-compliant metadata. Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. Esri grid format Esri ArcGIS 10.2.2 Zip file contains the grid of backscatter as well as the associated metadata files. 11 https://www.sciencebase.gov/catalog/file/get/560efc6ce4b0ba4884c5ed32 https://www.sciencebase.gov/catalog/item/560efc6ce4b0ba4884c5ed32 https://doi.org/10.5066/F7HM56HK Data can be downloaded using the Network Resource Links. The first link is a direct link to download a zipped file with the data and metadata. The second link is to the page containing the data. The third link is to the publication landing page. None 20220825 U.S. Geological Survey, Pacific Coastal and Marine Science Center PCMSC Science Data Coordinator mailing and physical

2885 Mission Street

Santa Cruz CA 95060 831-427-4747 pcmsc_data@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998