Browsing by Subject "Ross Sea"
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Item A new account of Ross Sea waters: characteristics, volumetrics, and variability(Texas A&M University, 2007-09-17) Stover, Christina LeeA new high-resolution climatology and volumetric ????-S census (???????? = 0.1????C, ????S = 0.01) is constructed for the Ross Sea. Property maps (potential temperature, salinity, and dissolved oxygen) along 40 depth levels and 21 neutral density (????n) surfaces are analyzed. A major inflow of Antarctic Surface Water (AASW) is observed branching off the westward-flowing coastal current near Cape Colbeck. One portion continues poleward hugging the coast while the other follows the shelf break to the west. The characteristic ??????V?????? shape of the Antarctic Slope Front over the western Ross Sea is indicated by a narrow stream of thickened AASW. The entire AASW layer shoals from east to west. Two major shoreward inflows of Lower Circumpolar Deep Water (LCDW) are inferred. A warm and salty tongue from the Balleny Gyre enters the Drygalski and Joides troughs. A similar tongue is exported from the Ross Gyre and enters the Glomar Challenger Trough. No significant LCDW inflow is observed over the eastern slope of the Ross Sea. The thickest outflows of Shelf Water (SW: ???? ?????? -1.85????C, S > 34.5) and new Antarctic Bottom Water (AABW: ???? > -1.85????C, ????n > 28.27 kg m-3) are found along the Drygalski and Joides troughs. Their saltiest (S > 34.7) components are concentrated in the western Ross Sea, whereas the low-salinity varieties are found throughout the Ross Sea shelf. The most voluminous water mass in the Ross Sea is LCDW. The least abundant is AABW found primarily over the western slope. Modified CDW (MCDW) in the western Ross is inferred to be a mixture of 30% AASW and 70% LCDW; whereas central (eastern) MCDW is 40% (60%) AASW and 60% (40%) LCDW. The same water mass composition is inferred for new AABW in the western and central Ross Sea: 25% SW and 75% MCDW. A 40-year freshening trend is detected at different sites along the coastal transit of AASW from Cape Colbeck to Ross Island. In addition to a freshening, the MCDW and high-salinity SW also reveal a cooling trend. Conversely, a warming and salinification is indicated at the main inflows of LCDW.Item The Ross Sea Response to Evolving Ocean-Ice Interactions in a Changing Climate(2012-12-03) Wiederwohl, Christina 1980-Early 1990s to late 2000s freshening (?S ? -0.001?0.002) and warming (?? ? 0.02?C?0.035?C) of bottom waters was detected in the southern Pacific Ocean, and Ross Sea source waters progressively freshened during the past four decades. This study investigates potential freshwater anomaly sources and quantifies their effect. Glacial melt water inputs to the GCT increased by 1.3 km^3 per decade (1976? 2007), more rapidly so after 2000 (6.8 km^3 per decade), freshening local Shelf Water by 0.0004 per decade. Lighter basal melt inputs to the LAT started in 1994 and also picked up after 2000 to 14.9 km^3 per decade, lowering the local Antarctic Surface Water salinity by -0.017 per decade. Upstream in the Amundsen Sea surface water freshened by -0.03 per decade (1994?2007) mostly (50%) from larger melt water inputs from the Pine Island (17.7 km^3 per decade) and Dotson (14.8 km^3 per decade) glaciers. Two decades of steady (1978-2000) strengthening of sea ice productivity (200 km^3 per decade) within the Ross Sea Polynya suddenly reversed to weakening (-98.6 km^3 per decade) and resulted in Shelf Water freshening (-0.02 per decade) thereafter. To fully account for the observed variability in Ross Sea waters, the progressive (1992- 2011) adjustment of the density field and induced advective contributions are estimated based on a simplified three-layer stratification. Eastern (western) inflow (outflow) of light surface (dense shelf) water increased by 28% (15%) to 1.11 Sv (1.01 Sv) by 2011; whereas a sluggish intermediate inflow (0.02 Sv) of Modified Circumpolar Deep Water turned into outflow after 2007, thus contributing 0.09 Sv by 2011 to the ventilation of deep waters farther offshore. The estimated evolution of overturning and advective salt fluxes in the Ross Sea yield overall freshening of water masses similar to those derived from observations. Volumetric mean salinities declined at -0.07 per decade for Antarctic Surface Water, -0.05 per decade for Modified Circumpolar Water, and -0.03 per decade for Shelf Water. Outflow intensification of Shelf Water mixtures is also consistent with bottom water property changes (freshening and warming) measured farther downstream in the southern Pacific Ocean.