![]() The presence of these three water masses in the Atlantic Ocean is evident in cross-sections of many water properties, including salinity, phosphate concentration and carbon isotope ratios (Figure 2). Antarctic Intermediate Water (AAIW) flows northward above NADW. AABW is confined to water depths below 4000 meters in the tropical and North Atlantic. Antarctic Bottom Water (AABW), which is formed close to Antarctica, is denser than NADW, and flows northward in the Atlantic below NADW. This North Atlantic Deep Water (NADW), as it is called, flows from the Atlantic to the Southern Ocean where much of it upwells - or rises to the surface - around Antarctica, and some of it circulates Antarctica before entering the rest of the world's deep oceans. Once dense enough, these waters sink and flow southward between ~ 10m. ![]() ![]() Warm salty tropical surface waters flowing northward in the western Atlantic cool in transit to and within the high-latitude North Atlantic, releasing heat to the overlying atmosphere and increasing seawater density. The Atlantic Ocean is the only ocean basin that features the transformation of surface-to-deepwater near both poles. Reconstructions of past ocean circulation using the geochemistry of microfossils preserved in marine sediments provide critical information to test these models. Instead, scientists use computer climate models to predict how the Earth's climate will change. Unfortunately the observations are too limited to provide insight into how the deep oceans and climate interact on the longer time scales of ocean circulation and also how this interaction might change in response to rising greenhouse gases. Subsequent measurements revealed that properties of deep water in key regions vary from decade to decade, and that these changes are linked to oscillations in surface climate (Dickson et al. The first field program to systematically measure physical and chemical properties of all the world's deep oceans took place from 1973–1978. ![]() However, knowledge of the deep oceans, their properties, and their climatic significance has been acquired relatively recently. Early seafaring nations recognized the practical and economic benefits of mapping surface currents and winds in great detail. ![]()
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