Abstract
AbstractOver the course of 10 months, the global Five Deeps Expedition (2018–2019) mapped ~550,000 km2 of seafloor of which 61% comprised new coverage over areas never before surveyed and ~30% was acquired from some of the ocean's deepest trenches and fracture zones. The deepest points of each ocean were mapped using a latest‐generation, full‐ocean depth Kongsberg EM 124 multibeam echosounder. These extreme depths were corrected using Conductivity, Temperature and Depth (CTD) data from sea surface to full ocean depth. The deepest place in each ocean were identified as the Brownson Deep, Puerto Rico Trench in the Atlantic Ocean (8,378 ± 5 m), an unnamed deep within the South Sandwich Trench in the Southern Ocean (7,432 ± 13 m), an unnamed deep within the Java Trench in the Indian Ocean (7,187 ± 13 m), Challenger Deep within the Mariana Trench in the Pacific Ocean (10,924 ± 15 m), and the Molloy Hole in the Arctic Ocean (5,551 ± 14 m). As part of the overarching mission of the Five Deeps Expedition, and to clarify beyond doubt the deepest point in the Indian, Pacific and Southern oceans, other sites were visited that had been postulated as potential deepest locations. This study has confirmed that the Horizon Deep within the Tonga Trench is the second deepest point in the Pacific Ocean (10,816 ± 16 m), the Dordrecht Deep within the Diamantina Fracture Zone is not the deepest point in the Indian Ocean (7,019 ± 17 m) and that in accordance with the guidelines of the Antarctic Treaty and International Hydrographic Organisation, although the Meteor Deep is the deepest point in the South Sandwich Trench (8,265 ± 13 m) it is located within the waters of the Atlantic Ocean and not the Southern Ocean.
Highlights
In 2018, the Five Deeps Expedition (FDE; www.fivedeeps. com) embarked on an ambitious privately-funded year-long round-the-world expedition to dive a two-person full ocean depth submersible to the deepest point in each of the Worlds five oceans (Atlantic, Southern, Indian, Pacific and Arctic; Figure 1)
Stewart and Jamieson (2019) reported on the pre-expedition study into this very question using the most up-to-date publically available bathymetric datasets at that time (primarily the Global Multi-R esolution Topography Synthesis (Ryan et al, 2009) which included processed multibeam bathymetry data donated by the international research community, global compilations from the General Bathymetric Chart of the Oceans (GEBCO_2014, version 20,141,103, www.gebco.net; Weatherall et al, 2015), the International Bathymetric Chart of the Southern Ocean (IBCSO; Arndt et al, 2013) and International Bathymetric Chart of the Arctic Ocean (IBCAO; Jakobsson et al, 2012)
The issues of exact depth and location of the deepest point were one of revisiting a number of named ‘deeps’ and determining whether these constituted real morphological features and to sound their exact depth. It was determined by Stewart and Jamieson (2019), with some certainty, that the Milwaukee Deep did not exist as per the guidelines for naming undersea features listed by the International Hydrographic Organization (IHO) and the Intergovernmental Oceanographic Commission (IOC), and that the Brownson Deep would host the deepest point
Summary
In 2018, the Five Deeps Expedition (FDE; www.fivedeeps. com) embarked on an ambitious privately-funded year-long round-the-world expedition to dive a two-person full ocean depth submersible to the deepest point in each of the Worlds five oceans (Atlantic, Southern, Indian, Pacific and Arctic; Figure 1). Stewart and Jamieson (2019) reported on the pre-expedition study into this very question using the most up-to-date publically available bathymetric datasets at that time (primarily the Global Multi-R esolution Topography Synthesis (Ryan et al, 2009) which included processed multibeam bathymetry data donated by the international research community, global compilations from the General Bathymetric Chart of the Oceans (GEBCO_2014, version 20,141,103, www.gebco.net; Weatherall et al, 2015), the International Bathymetric Chart of the Southern Ocean (IBCSO; Arndt et al, 2013) and International Bathymetric Chart of the Arctic Ocean (IBCAO; Jakobsson et al, 2012) They concluded that while the deepest parts of some oceans were relatively well known, others had multiple ‘deeps’ which may be contenders for the deepest point in a particular trench or even ocean, while in other oceans due to a paucity of high-resolution data there was considerable doubt as to the exact location of the deepest point, let alone accuracy of that depth measurement. We report on high-precision full-ocean depth multibeam echosounder data acquired using the Kongsberg EM 124 system, corrected with high-resolution, full-ocean depth Conductivity, Temperature and Depth (CTD) data to validate the greatest depths of our five oceans
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