User:سائغ/T3
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In 2014, a study was conducted regarding the determination of the depth and location of the Challenger Deep based on data collected previous to and during the 2010 sonar mapping of the Mariana Trench with a Kongsberg Maritime EM 122 multibeam echosounder system aboard USNS Sumner. This study by James. V. Gardner et al. of the Center for Coastal & Ocean Mapping-Joint Hydrographic Center (CCOM/JHC), Chase Ocean Engineering Laboratory of the University of New Hampshire splits the measurement attempt history into three main groups: early single-beam echo sounders (1950s–1970s), early multibeam echo sounders (1980s – 21st century), and modern (i.e., post-GPS, high-resolution) multibeam echo sounders. Taking uncertainties in depth measurements and position estimation into account the raw data of the 2010 bathymetry of the Challenger Deep vicinity consisting of 2,051,371 soundings from eight survey lines was analyzed. The study concludes that with the best of 2010 multibeam echosounder technologies after the analysis a depth uncertainty of ±25 m (82 ft) (95% confidence level) on 9 degrees of freedom and a positional uncertainty of ±20 to 25 m (66 to 82 ft) (2drms) remain and the location of the deepest depth recorded in the 2010 mapping is 10,984 m (36,037 ft) at 11.329903°N 142.199305°E / 11.329903; 142.199305. The depth measurement uncertainty is a composite of measured uncertainties in the spatial variations in sound-speed through the water volume, the ray-tracing and bottom-detection algorithms of the multibeam system, the accuracies and calibration of the motion sensor and navigation systems, estimates of spherical spreading, attenuation throughout the water volume, and so forth.[1]
Both the RV Sonne expedition in 2016, and the RV Sally Ride expedition in 2019 expressed strong reservations concerning the depth corrections applied by the Gardner et al. study of 2014, and serious doubt concerning the accuracy of the deepest depth calculated by Gardner (in the western basin), of 10,984 m (36,037 ft) after analysis of their multibeam data on a 100 m (328 ft) grid. Dr. Hans van Haren, chief scientist on the RV Sally Ride cruise SR1916, indicated that Gardner's calculations were 69 m (226 ft) too deep due to the "sound velocity profiling by Gardner et al. (2014)."[2]
In 2018-2019 the deepest points of each ocean were mapped using a full‐ocean depth Kongsberg EM 124 multibeam echosounder abord DSSV Pressure Drop. In 2021 a data paper was published by Cassandra Bongiovanni, Heather A. Stewart and Alan J. Jamieson regarding the gathered data donated to GEBCO. The deepest depth recorded in the 2019 Challenger Deep sonar mapping was 10,924 m (35,840 ft) ±15 m (49 ft) at 11.369°N 142.587°E / 11.369; 142.587 in the eastern basin. This depth closely agrees with the deepest point (10,925 m (35,843 ft) ±12 m (39 ft)) determined by the Van Haren et al. sonar bathymetry. The geodetic position of the deepest depth according to the Van Haren et al. significantly differs (about 42 km (26 mi) to the west) with the 2021 paper. After post-processing the initial depth estimates by application of a full-ocean depth sound velocity profile Bongiovanni et al. report an (almost) as deep point at 11.331°N 142.205°E / 11.331; 142.205 in the western basin that geodetically differs about 350 m (1,150 ft) with the deepest point position determined by Van Haren et al. (11.332417°N 142.20205°E / 11.332417; 142.20205 in the western basin). After analysis of their multibeam data on a 75 m (246 ft) grid the Bongiovanni et al. 2021 paper states the technological accuracy does not currently exist on low-frequency ship-mounted sonars required to determine which location was truly the deepest, nor does it currently exist on deep-sea pressure sensors.[3]
In 2021 a study by Samuel F. Greenaway, Kathryn D. Sullivan, Samuel H. Umfress, Alice B. Beittel and Karl D. Wagner was published presenting a revised estimate of the maximum depth of the Challenger Deep based on a series of submersible dives conducted in June 2020. These depth estimates are derived from acoustic echo sounding profiles referenced to in-situ direct pressure measurements and corrected for observed oceanographic properties of the water-column, atmospheric pressure, gravity and gravity-gradient anomalies, and water-level effects. The study concludes according to their calculations the deepest observed seafloor depth was 10,935 m (35,876 ft) ±6 m (20 ft) below mean sea level at a 95% condidence level at 11°22.3′N 142°35.3′E in the eastern basin. For this estimate, the error term is dominated by the uncertainty of the employed pressure sensor, but Greenaway et al. show that the gravity correction is also substantial. The Greenaway et al. study compares its results with other recent acoustic and pressure-based measurements for the Challenger Deep and concluds the deepest depth in the western basin is very nearly as deep as the eastern basin. The disagreement between the maximum depth estimates and their geodetic positions between post-2000 published dephts however exceed the accompanying margins of uncertainty, raising questions ragarding the measurements or the reported uncertainties.[4]
Another 2021 paper by Scott Loranger, David Barclay and Michael Buckingham, besides an implosion shock wave based depth estimate, also treatises the differences between various maximum depth estimates and their geodetic positions.[5]