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Minimal change in Antarctic Circumpolar Current flow speed between the last glacial and Holocene

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first_imgThe Antarctic Circumpolar Current is key to the mixing and ventilation of the world’s oceans. This current flows from west to east between about 45° and 70°S connecting the Atlantic, Pacific and Indian oceans, and is driven by westerly winds and buoyancy forcing. High levels of productivity in the current regulate atmospheric CO2 concentrations. Reconstructions of the current during the last glacial period suggest that flow speeds were faster or similar to present, and it is uncertain whether the strength and position of the westerly winds changed. Here we reconstruct Antarctic Circumpolar Current bottom speeds through the constricting Drake Passage and Scotia Sea during the Last Glacial Maximum and Holocene based on the mean grain size of sortable silt from a suite of sediment cores. We find essentially no change in bottom flow speeds through the region, and, given that the momentum imparted by winds, and modulated by sea-ice cover, is balanced by the interaction of these flows with the seabed, this argues against substantial changes in wind stress. However, glacial flow speeds in the sea-ice zone south of 56°S were significantly slower than present, whereas flow in the north was faster, but not significantly so. We suggest that slower flow over the rough topography south of 56°S may have reduced diapycnal mixing in this region during the last glacial period, possibly reducing the diapycnal contribution to the Southern Ocean overturning circulation.last_img read more

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South Korea cleared to buy six P-8As under $2.1b contract

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first_img View post tag: MPA The US State Department has approved the potential sale of six P-8A patrol aircraft to the Republic of Korea under an estimated $2.1 billion contract.South Korea’s decision to pick Boeing’s P-8A Poseidon as its new maritime patrol aircraft was made known in June this year. The P-8A would replace the fleet of P-3C Orion MPAs which entered service in the 1990s.In addition to the six aircraft, the $2.1b figure includes multifunctional information distribution system joint tactical radio systems for each aircraft and tactical operations centers (TOC).Also included are GPS/Inertial Navigations Systems (EGIs), AN/AAR-54 missile warning sensors, commercial engines, tactical open mission software (TOMS), electro-optical (EO) and infrared (IO) MX-20HD, the AN/AAQ-2(V)1 acoustic system, AN/APY-10 radar, ALQ-240 electronic support measures, AN/ALE-47 countermeasures dispensing system, in addition to support equipment and training and operations assistance.Should the deal be finalized, the Republic of Korea will become the seventh nation to operate the Boeing-built P-8A Poseidon, joining the US, Australia, the UK, Norway and India. New Zealand is the most recent P-8A customer, having announced a NZD2.346 billion contract for the acquisition of four aircraft in July this year.Boeing’s aircraft was selected over those proposed by Airbus and Saab who had also shown interest in the South Korean MPA contract.The P-8A is a derivative of a modified Boeing 737-800ERX airliner, featuring a high-bypass turbo fan jet engine with a fully connected, open architecture mission system. The armament of the Poseidon consists of five internal and six external stations for AGM-84H/K SLAM-ER, AGM-84 Harpoon, Mark 54 torpedo, and a High Altitude Anti-Submarine Warfare Weapon system among others.Development of the P-8A program was started in June 2004 when the US Navy selected the Boeing multimission maritime aircraft, 737 MMA, as the best successor to the P-3C Orion maritime patrol aircraft View post tag: ROK Navy View post tag: Poseidon P-8Acenter_img Photo: US Navy file photo of a P-8A Poseidon MPA Share this articlelast_img read more

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