Distribution of Oxygen Isotope Ratio of Precipitation in the Atlantic-Indian Sectors of the Southern Ocean

Abstract

Herein, the spatial distribution of stable oxygen isotope ratios (δ 18 O) of precipitation in the Atlantic to Indian sectors of the Southern Ocean is examined using the results of in situ observations and numerical modeling. In situ observations of 59 precipitation events reveal poleward decrease of δ 18 O, with a larger meridional gradient south of 60°S. Moreover, the estimates from the observations and model (IsoGSM) agree reasonably well, with a mean absolute difference of 4.3‰. Thus, the IsoGSM results generally support the observed poleward increase in the meridional gradient. These results will prove valuable in investigating the atmospheric water cycle and in studying oceanic processes of water mass formation and transport.

Influence of large‐scale atmospheric circulation on marine air intrusion toward the East Antarctic coast

“…By contrast, the PDF for the cold ice‐free ocean (SST < 10°C) falls below the evaporation curve and depicts a large spread toward the PDF for the ice‐covered ocean. The isotopic composition of precipitation observed in earlier JARE cruises also exhibits a decreasing trend with latitude in this region (south of 60°'S) [ Nakamura et al , ]. These results suggest that southward/northward winds associated with cyclones transport moisture with enriched/depleted δ D values to the observation site.…”

Changes in water properties and flow regime on the continental shelf off the Adélie/George VLand coast, East Antarctica, after glacier tongue calving

“…From the δ 18 O‐S diagram, it was clear that δ 18 O was shifted to lower values from 2001 to 2011/2015 in AD box (Figure ).The envelope line connecting the δ 18 O‐S properties for the temporal changes has been extrapolated to the line of zero salinity to give the tendency of added freshwater end‐member and/or changes in end‐member contribution ratio. In the AD box, at the surface (0–50 dbar average) the line through the 2001 and 2011 data extrapolates to a fresh water δ 18 O of −31‰, and that through the 2001 and 2015 data to −19‰; the value of the former is close to continental ice and the latter to local precipitation [ Nakamura et al ., ]. The envelope for intermediate and deep layers (from 150–650 dbar) is −50 to −200‰, which cannot be explained by a simple mixture of known freshwater end‐members.…”

El Niño Southern Oscillation Signature in Atmospheric Water Isotopes over Maritime Continent during Wet Season

“…The performance of IsoGSM in producing atmospheric isotopic variability data has been evaluated in several previous studies. Simulated IsoGSM data show good agreement with observed isotopic spatiotemporal variability, suggesting that the model can reproduce the dynamics of atmospheric moisture transport satisfactorily (Berkelhammer et al 2012;Ishizaki et al 2012;Nakamura et al 2014;Okazaki et al 2015). In this study, the simulated stable isotope ratios in the precipitation data over the JAMSTEC and GNIP stations were correlated significantly with the observations (significance exceeding 95 %); the root mean square errors (RMSEs) were 1.71-2.98 ‰ for δ 18 O, while the standard deviations (σ) of the observed isotopes were 1.73-3.01 ‰.…”