Abstract

Seep Searching: Analysis of Multibeam Sonar Data Reveals Hundreds of Gas Seeps Along the U.S. Atlantic Continental Margin

Mali'o Kodis
Adam Skarke (Mentor)
Center for Coastal and Ocean Mapping (CCOM), University of New Hampshire
Office of Exploration and Research
National Oceanographic and Atmospheric Administration (NOAA)

Approximately 450 seafloor methane seeps were identified along the U.S. Atlantic continental margin between Cape Romain, South Carolina and Cape Cod, Massachusetts at depths ranging from 54 meters to 2,650 meters. The seeps were detected through analysis of acoustic water column backscatter data collected with a 30 khZ multibeam sonar on NOAA Ship Okeanos Explorer between 2011 and 2013. Prior to this investigation, less than 50 gas seeps were known to exist in the region, all of which were identified within the last year by NOAA Ship Okeanos Explorer. Prior to 2012, only one gas seep was known to exist on the U.S. Atlantic continental margin. The location and abundance of these newly discovered gas seeps holds significant implications for research on the ocean carbon cycle, ocean acidification processes, and submarine slope stability (Hill, 2004; Newman, 2007; Brothers, 2013). Multiple investigators have predicted the existence of gas seeps along the southern U.S. Atlantic continental margin (Klauda and Sandler, 2004; Milkov, 2003; Schmuck and Paull, 1993) however, prior to this investigation, there was no regional scale data set with which to ground-truth these predictions. Further detection efforts and sampling of these newly discovered seeps will facilitate determination of gas chemistry, sources, and transport pathways. Additionally, this data set will provide a reliable basis for the evaluation of automated detection algorithms currently under development.

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Milkov, A.V. "Worldwide Distribution of Submarine Mud Volcanoes and Associated Gas Hydrates." Marine Geology 167.1-2 (2000): 29-42.
Newman, K., M. Cormier, J. Weissel, N. Driscoll, M. Kastner, E. Solomon, G. Robertson, J. Hill, H. Singh, and R. Camilli. "Active Methane Venting Observed at Giant Pockmarks along the U.S. Mid-Atlantic Shelf Break." Earth and Planetary Science Letters 267 (2008): 341-52.
Schmuck, E. A., and C. K. Paull. "Evidence for Gas Accumulation Associated with Diapirism and Gas Hydrates at the Head of the Cape Fear Slide." Geo-Marine Letters 13.3 (1993): 145-52

Coastal Lidar Vertical Uncertainty Analysis in Hurricane Sandy Impact Region

Matthew Sharr
Steve Matula (Mentor)
Chris Parrish (Co-Mentor)
National Ocean Service (NOS) / National Geodetic Survey (NGS)
National Oceanic and Atmospheric Administration (NOAA)

NOAA and other agencies are currently involved in acquisition and analysis of airborne light detection and ranging (lidar) data in the region impacted by Hurricane Sandy. These data are being used to support response efforts, shoreline change analysis, storm vulnerability modeling, and habitat assessments. However, a prerequisite step in assessing the suitability of the data for any particular application is to conduct a vertical uncertainty (or “accuracy”) assessment. One method of assessing the accuracy of a lidar data set is to compare the lidar-derived heights to Ground Control Points (GPCs). This project entailed collecting GPCs using Global Positioning System (GPS) technology in Island Beach State Park, NJ. GPS is a fast and accurate way of obtaining GPCs. Once GPCs were collected and processed, available lidar data were tested using a variety of both open source and commercial software packages available for processing lidar data. The primary data used in this study were provided by the U.S. Geological Survey (USGS) and collected immediately before and after Hurricane Sandy using a new, state-of-the-art research lidar, the EAARL-B. However, the procedures were designed such that they can be applied to other data, as well. Specific project goals included evaluating and developing procedures for performing the lidar accuracy assessments using various software packages, and making recommendations for future use in lidar processing. The software packages that were used in this project were Applied Imagery Quick Terrain Modeler (QT Modeler), QCoherent LP360, and LAStools. Procedures for using each of these software packages have been written and will be available to various audiences. In this presentation, I will discuss the results of the accuracy assessments, evaluation of the different software packages, and recommendations for NOAA NGS in further assessing lidar data in the Sandy-impact area.

Publication Date

7-26-2013

Document Type

Presentation

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