In situ measurements of sea surface temperature (SST), salinity (SSS), Total Alkalinity (A_T) and Total Carbon (C_T) were obtained during austral summer (mid-February to mid-March) from 2005 to 2019 in the Southern Ocean (SO), along a transect between Hobart, Tasmania and Dumont d'Urville French Antarctic Station. The studied transect is divided in four regions from North to South: the Subtropical Zone (STZ), the Subantarctic Region (SAR), the Antarctic Region (AAR) and the Coastal Antarctic Zone (CAZ). Latitudinal distribution of measured SST, SSS, A_T, C_T as well as calculated pH, CO₂ parameters (seawater fugacity of CO₂ (fCO_2sw), difference between seawater and atmospheric fCO₂ (ΔfCO₂), CO₂ flux (FCO₂)) and satellite-derived Chlorophyll a (Chl-a) are discussed. We show that the variability of physical and carbonate parameters in the STZ and north of the SAR are related to the mesoscale activity. In the CAZ, the freshwater inputs from sea-ice melting strongly impact the variability of all parameters. The comparison between physical and carbonate parameters highlights that A_T and C_T are directly related to the latitudinal variability of SST and SSS. Study of the CO₂ parameters shows that the transect is a sink of CO₂ during February and March, with a mean FCO₂ of -4.0 ± 2.8 mmol m^-2 d^-1. The most negative values of FCO₂ are found in the STZ and SAR north of 50°S and in the AAR south of 62°S, where biological activity is high. New simple empirical relationships are developed for A_T from SST and SSS and for C_T using SST, SSS and atmospheric fCO₂ (fCO_2atm) for the austral summer in the studied area. Using high resolution SSS and SST from the SURVOSTRAL program, trends of A_T and C_T are determined in the SAR and the AAR from 2005 to 2019. SST, SSS and A_T increase over this period in the SAR, which might be explained by the southward migration of the Subtropical Front. In the AAR, no clear trend is detected. C_T increases by 1.0 ± 0.2 and 0.8 ± 0.3 μmol kg^-1 yr^-1 in the SAR and AAR respectively. The trend in the AAR is attributed to the increase in anthropogenic CO₂ emissions in the atmosphere while, in the SAR, hydrographic changes also contribute to the increase. Using the coefficient associated with fCO_2atm in the equation of C_T, we estimate the impact of atmospheric CO₂ increase on C_T at 1.18 ± 0.14 μmol kg^-1 yr^-1 and 1.07 ± 0.13 μmol kg^-1 yr^-1 in the SAR and AAR respectively. Decreases in pH are observed in both regions (-0.0018 ± 0.0001 and -0.0026 ± 0.0003 yr^-1 in the SAR and AAR respectively), indicating the sensitivity of surface waters in the area towards the development of ocean acidification processes under rising anthropogenic emissions.