Neodymium isotopic characterization of Ross Sea Bottom Water and its advection through the southern South Pacific

Abstract The Antarctic continental margin supplies the densest bottom water to the global abyss. From the late twentieth century, an acceleration in the long-term freshening of Antarctic Bottom Waters (AABW) has been detected in the Australian-Antarctic Basin. Our latest hydrographic observations reveal that, in the late 2010s, the freshening trend has reversed broadly over the continental slope. Near-bottom salinities in 2018–2019 were higher than during 2011–2015. Along 170° E, the salinity increase between 2011 and 2018 was greater than that observed in the west. The layer thickness of the densest AABW increased during the 2010s, suggesting that the Ross Sea Bottom Water intensification was a major source of the salinity increase. Freshwater content on the continental slope decreased at a rate of 58 ± 37 Gt/a in the near-bottom layer. The decadal change is very likely due to changes in Ross Sea shelf water attributable to a decrease in meltwater from West Antarctic ice shelves for the corresponding period.

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Influence of Ross Sea Bottom Water changes on the warming and freshening of the Antarctic Bottom Water in the Australian-Antarctic Basin

Ocean Science Discussions ◽

10.5194/osd-8-2197-2011 ◽

2011 ◽

Vol 8 (6) ◽

pp. 2197-2235 ◽

Cited By ~ 1

Author(s):

K. Shimada ◽

S. Aoki ◽

K. I. Ohshima ◽

S. R. Rintoul

Keyword(s):

Bottom Water ◽

Ross Sea ◽

Potential Temperature ◽

Volume Transport ◽

Shelf Water ◽

Antarctic Bottom Water ◽

Vertical Diffusion ◽

Sea Bottom ◽

The Antarctic ◽

Source Waters

Abstract. The WOCE Hydrographic Program (WHP) and repeated hydrographic data were used to document overall property changes of the Antarctic Bottom Water (AABW) in the Australian-Antarctic Basin between the 1990s and 2000s. Strong cooling and freshening is observed on isopycnals for layers denser than γn = 28.30. Changes in average salinity and potential temperature below this isopycnal correspond to basin-wide warming of 1300 &pm; 200 TW and freshening of 24 &pm; 3 Gt yr−1. While freshening can be explained by freshening of major source waters, i.e., the High Salinity Shelf Water (HSSW) of the Ross Sea and the dense shelf water formed in the Adélie and George V Land (AGVL) region, extensive warming of the AABW cannot be explained by warming of the source waters. A possible cause of warming of the AABW is a decrease in supply of the Ross Sea Bottom Water (RSBW). Hydrographic profiles between the Drygalski Trough of the Western Ross Sea and 150° E were analyzed in the context of a simple advective-diffusive model to assess the causes of the observed changes. The RSBW has also warmed by a larger amount than its source water (the HSSW). The model suggests that the warming of the RSBW observed between the 1970s and 2000s can be explained by a 21 &pm; 23% reduction in transport of the RSBW and an enhancement of the vertical diffusion of heat as a result of a 30 &pm; 7% weakening of the abyssal stratification. Freshening of the HSSW reduced the salinity and density stratification between the bottom water layer and overlying ambient water. Hence, freshening of the HSSW both directly freshened and indirectly warmed the RSBW by enhancing the vertical mixing. A simple box model suggest that changes in property and volume transport (decrease of 6.7% is assumed between the year 1995 and 2005) of the RSBW can explain 51 &pm; 6% of the warming and 84 &pm; 10% of the freshening observed in the AABW. These facts demonstrate that changes in both property and volume transport of the RSBW have contributed to the warming and freshening of the AABW in the Australian-Antarctic Basin.

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Influence of Ross Sea Bottom Water changes on the warming and freshening of the Antarctic Bottom Water in the Australian-Antarctic Basin

Ocean Science ◽

10.5194/os-8-419-2012 ◽

2012 ◽

Vol 8 (4) ◽

pp. 419-432 ◽

Cited By ~ 26

Author(s):

K. Shimada ◽

S. Aoki ◽

K. I. Ohshima ◽

S. R. Rintoul

Keyword(s):

Bottom Water ◽

Ross Sea ◽

Potential Temperature ◽

Volume Transport ◽

Alternative Mechanism ◽

Shelf Water ◽

Antarctic Bottom Water ◽

Vertical Diffusion ◽

Sea Bottom ◽

Using Data

Abstract. Changes to the properties of Antarctic Bottom Water in the Australian-Antarctic Basin (AA-AABW) between the 1990s and 2000s are documented using data from the WOCE Hydrographic Program (WHP) and repeated hydrographic surveys. Strong cooling and freshening are observed on isopycnal layers denser than γn = 28.30 kg m−3. Changes in the average salinity and potential temperature below this isopycnal correspond to a basin-wide warming of 1300 ± 200 GW and freshening of 24 ± 3 Gt year−1. Recent changes to dense shelf water in the source regions in the Ross Sea and George V Land can explain the freshening of AA-AABW but not its extensive warming. An alternative mechanism for this warming is a decrease in the supply of AABW from the Ross Sea (RSBW). Hydrographic profiles between the western Ross Sea and George V Land (171–158° E) were analyzed with a simple advective-diffusive model to assess the causes of the observed changes. The model suggests that the warming of RSBW observed between the 1970s and 2000s can be explained by a 21 ± 23% reduction in RSBW transport and the enhancement of the vertical diffusion of heat resulting from a 30 ± 7% weakening of the abyssal stratification. The documented freshening of Ross Sea dense shelf water leads to a reduction in both salinity and density stratification. Therefore the direct freshening of RSBW at its source also produces an indirect warming of the RSBW. A simple box model suggests that the changes in RSBW properties and volume transport (a decrease of 6.7% is assumed between the year 1995 and 2005) can explain 51 ± 6% of the warming and 84 ± 10% of the freshening observed in AA-AABW.

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An east-west contrasting changes of Antarctic Bottom Water properties in the Southern Indian Ocean over the last three decades

10.5194/egusphere-egu21-10585 ◽

2021 ◽

Author(s):

Yeon Choi ◽

SungHyun Nam

Keyword(s):

Indian Ocean ◽

Deep Water ◽

Bottom Water ◽

Ross Sea ◽

Weddell Sea ◽

Southern Indian Ocean ◽

Antarctic Bottom Water ◽

Sea Bottom ◽

East West ◽

Source Waters

Physical properties of Antarctic Bottom Water (AABW) derived from mixture of multiple source waters of different properties, are significantly affected by and contribute to the climate change. This study reveals a contrasting east-west pattern of changes in AABW temperature and salinity in the Southern Indian Ocean (SIO), which continues to become warmer (0.04 &#177; 0.01&#176;C/decade) and more saline (0.002 &#177; 0.001 kg/g/decade) in the western SIO whereas warmer (0.03 &#177; 0.01&#176;C/decade) and fresher (-0.004 &#177; 0.001 kg/g/decade) in the eastern SIO over the past three decades, based on repeat hydrographic observations along meridional lines (1993, 1996, 2008, and 2019 in the western SIO and 1995, 2004, and 2012 in the eastern SIO). Warming and salinification of AABW consisting of the Cape Darnley Bottom Water (CDBW), Weddell Sea Deep Water (WSDW), and Lower Circumpolar Deep Water (LCDW) in the western SIO, are explained by changing proportion of source waters during the period, e.g., decreasing portion of relatively fresh CDBW (from 68% to 59%), and increasing portions of saline WSDW (from 30% to 34%) and warm and saline LCDW (from 2% to 7%). In contrast, in the eastern SIO, warming and freshening of the AABW consisting of the Ross Sea Bottom Water (RSBW), Ad&#233;lie Land Bottom Water (ALBW), and LCDW are not explained by the changing proportion but properties of the source waters during the period, e.g., warming and freshening of RSBW (0.08&#176;C/decade and -0.013 kg/g/decade) and ALBW (0.01&#176;C/decade and -0.008 kg/g/decade). The east-west contrasting changes of AABW properties (eastern freshening and western salinification) over the last three decades have important consequences within and beyond the SIO.

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Rebound of shelf water salinity in the Ross Sea

Nature Communications ◽

10.1038/s41467-019-13083-8 ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 11

Author(s):

Pasquale Castagno ◽

Vincenzo Capozzi ◽

Giacomo R. DiTullio ◽

Pierpaolo Falco ◽

Giannetta Fusco ◽

...

Keyword(s):

Large Scale ◽

Bottom Water ◽

High Salinity ◽

Ross Sea ◽

Shelf Water ◽

Antarctic Bottom Water ◽

Sea Bottom ◽

Salinity Increase ◽

Interannual Fluctuations ◽

Observational Record

AbstractAntarctic Bottom Water (AABW) supplies the lower limb of the global overturning circulation and ventilates the abyssal ocean. In recent decades, AABW has warmed, freshened and reduced in volume. Ross Sea Bottom Water (RSBW), the second largest source of AABW, has experienced the largest freshening. Here we use 23 years of summer measurements to document temporal variability in the salinity of the Ross Sea High Salinity Shelf Water (HSSW), a precursor to RSBW. HSSW salinity decreased between 1995 and 2014, consistent with freshening observed between 1958 and 2008. However, HSSW salinity rebounded sharply after 2014, with values in 2018 similar to those observed in the mid-late 1990s. Near-synchronous interannual fluctuations in salinity observed at five locations on the continental shelf suggest that upstream preconditioning and large-scale forcing influence HSSW salinity. The rate, magnitude and duration of the recent salinity increase are unusual in the context of the (sparse) observational record.

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HYDROCHEMICAL AND ISOTOPIC CHARACTERIZATION OF GROUNDWATER FLOW SYSTEMS IN NORTH-CENTRAL MEXICO: IMPLICATIONS FOR WATER MANAGEMENT

10.1130/abs/2020sc-343820 ◽

2020 ◽

Author(s):

Antonio Cardona ◽

◽

Cristian Abraham Rivera-Armendariz ◽

Socrates Alonso Torres ◽

Isidro Montes-Avila

Keyword(s):

Water Management ◽

Groundwater Flow ◽

Central Mexico ◽

North Central ◽

Groundwater Flow Systems ◽

Flow Systems ◽

Isotopic Characterization

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Stable isotopic characterization of nitrate wet deposition in the tropical urban atmosphere of Costa Rica

Environmental Science and Pollution Research ◽

10.1007/s11356-021-15327-x ◽

2021 ◽

Author(s):

Mario Villalobos-Forbes ◽

Germain Esquivel-Hernández ◽

Ricardo Sánchez-Murillo ◽

Rolando Sánchez-Gutiérrez ◽

Ioannis Matiatos

Keyword(s):

Costa Rica ◽

Wet Deposition ◽

Urban Atmosphere ◽

Stable Isotopic ◽

Isotopic Characterization

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Elemental and Isotopic Characterization of Tobacco from Umbria

Metabolites ◽

10.3390/metabo11030186 ◽

2021 ◽

Vol 11 (3) ◽

pp. 186

Author(s):

Luana Bontempo ◽

Daniela Bertoldi ◽

Pietro Franceschi ◽

Fabio Rossi ◽

Roberto Larcher

Keyword(s):

Stable Isotope ◽

Economic Value ◽

Isotope Ratios ◽

Stable Isotope Ratios ◽

Umbria Region ◽

Geographical Regions ◽

Isotopic Characterization ◽

First Time ◽

Micro Elements

Umbrian tobacco of the Virginia Bright variety is one of the most appreciated tobaccos in Europe, and one characterized by an excellent yield. In recent years, the Umbria region and local producers have invested in introducing novel practices (for production and processing) focused on environmental, social, and economic sustainability. Due to this, tobacco from Umbria is a leading commodity in the global tobacco industry, and it claims a high economic value. The aim of this study is then to assess if elemental and isotopic compositions can be used to protect the quality and geographical traceability of this particular tobacco. For the first time the characteristic value ranges of the stable isotope ratios of the bio-elements as a whole (δ2H, δ13C, δ15N, δ18O, and δ34S) and of the concentration of 56 macro- and micro-elements are now available, determined in Virginia Bright tobacco produced in two different areas of Italy (Umbria and Veneto), and from other worldwide geographical regions. The ranges of variability of elements and stable isotope ratios had slightly different results, according to the three geographical origins considered. In particular, Umbria samples presented significantly lower content of metals potentially dangerous for human health. The results of this first exploratory work highlight the possibility of characterizing tobacco from Umbria, and suggest widening the scope of the survey throughout Italy and foreign regions, in order to be used to describe the geographical origin of tobacco in general and verify the origin of the products on the market.

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