A long time series of XBT data collected during Austral summers and satellite altimetry data south of New Zealand are used to identify the positions of the main Antarctic Circumpolar Current (ACC) fronts and their branches from 1994 to 2015. The study area has been investigated since 1994 in the framework of the Climatic Long-term Interaction for the Mass balance in Antarctica (CLIMA), the Southern Ocean Chokepoints Italian Contribution (SOChIC) and the Marine Observatory in the Ross Sea (MORSEA) projects of the Italian National Research Program in Antarctica (PNRA). During these projects, in situ temperature sections of the surface layer (0-800 m) of the Southern Ocean along the track New Zealand-Ross Sea have been occupied almost every summer season by means of XBT. The flow of the ACC is well known to be concentrated in several jets associated with fronts, or regions of strong horizontal gradients in water mass properties and sea surface height. These fronts are linked to particular water mass features, allowing simple criteria based on temperature and salinity to be used to locate them. In this study regional thermal criteria have been used for the detection of ACC fronts from in situ XBT data. The positions of ACC fronts from in situ XBT data agree with existing literature even if a slight increase in the standard deviation during last years is found and the indication of a southward trend in the positions of fronts is shown. Moreover, satellite altimetry data provided by AVISO have been used to identify the positions of the fronts on the basis of specific dynamic height values usually associated to each front as well as through the location on the maximum Absolute Dynamic Topography gradient within a predetermined frontal region. Both altimetry-based methods allowed us to partially fill the gap between consecutive in situ measurements and offered different results. These positions have been compared with those determined from in situ data and finally results from the three identification methods are discussed.
Position of main ACC fronts south of New Zealand from satellite altimetry and XBT data in the period 1994-2015
Cotroneo Y.;Aulicino G.;Budillon G.;Fusco G.;Spezie G.
2016-01-01
Abstract
A long time series of XBT data collected during Austral summers and satellite altimetry data south of New Zealand are used to identify the positions of the main Antarctic Circumpolar Current (ACC) fronts and their branches from 1994 to 2015. The study area has been investigated since 1994 in the framework of the Climatic Long-term Interaction for the Mass balance in Antarctica (CLIMA), the Southern Ocean Chokepoints Italian Contribution (SOChIC) and the Marine Observatory in the Ross Sea (MORSEA) projects of the Italian National Research Program in Antarctica (PNRA). During these projects, in situ temperature sections of the surface layer (0-800 m) of the Southern Ocean along the track New Zealand-Ross Sea have been occupied almost every summer season by means of XBT. The flow of the ACC is well known to be concentrated in several jets associated with fronts, or regions of strong horizontal gradients in water mass properties and sea surface height. These fronts are linked to particular water mass features, allowing simple criteria based on temperature and salinity to be used to locate them. In this study regional thermal criteria have been used for the detection of ACC fronts from in situ XBT data. The positions of ACC fronts from in situ XBT data agree with existing literature even if a slight increase in the standard deviation during last years is found and the indication of a southward trend in the positions of fronts is shown. Moreover, satellite altimetry data provided by AVISO have been used to identify the positions of the fronts on the basis of specific dynamic height values usually associated to each front as well as through the location on the maximum Absolute Dynamic Topography gradient within a predetermined frontal region. Both altimetry-based methods allowed us to partially fill the gap between consecutive in situ measurements and offered different results. These positions have been compared with those determined from in situ data and finally results from the three identification methods are discussed.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
