We present here the final 100-meter cell size grid projection EPSG:9354 and metadata from the ISOBatA PNRA project, shared with the Alfred Wegener Institute (AWI) as part of the International Bathymetric Chart of the Southern Ocean (IBCSO). This dataset was collected by the ISOBatA project team using the Kongsberg EM304 multibeam system installed on the R/V Laura Bassi. The dataset processed and quality-controlled using QPS Qimera software and corrected for sound velocity using XBT and CTD data (courtesy of the MORSEA project), has been provided to AWI (IBCSO) and is archived here to ensure traceability, wide dissemination, and future usability.

The PNRA-funded project ISOBatA (Italian Southern Ocean Bathymetry from consistent exploitation of opportunistic seafloor datasets in the Antarctic region and surrounding areas) introduced an innovative approach to optimize the collection of acoustic (mainly bathymetric) and magnetometric data.

The primary objective of the project was to improve the bathymetric understanding of the Southern Ocean by collecting multibeam echosounder data during the Laura Bassi expeditions, focusing on previously unexplored areas in the Ross Sea and in the region between the Macquarie Triple Junction (MQ TJ) and the Emerald Fracture Zone (EMZ).

The operational phase of ISOBatA spanned three expeditions: XXXVII (2021-2022), XXXVIII (2023), and XXXIX (2024) of the Laura Bassi in Antarctica. In the first two years (XXXVII and XXXVIII), the project benefited from dedicated ship time, which enabled efficient data collection through strategic speed reductions during transfers and route adjustments along pre-identified corridors. Data collection was planned based on pre-existing metadata, such as IBCSO coverage, the Seismic Data Library (SDL), Italian Mooring Sites, and Italian Coring and Box Coring Sites. This also included transit routes through the Southern Ocean along the MQ and EMZ, as well as unmapped areas in the Ross Sea, such as the Italian MORSEA Mooring Sites.

In the third year (XXXIX), no dedicated ship time was available. Nevertheless, ISOBatA managed to collect data under two conditions: 1) without changing the ship's course or speed and 2) by simultaneously collecting acoustic data for other projects, which affected the spatial resolution of the data collected with EM304.

Despite the challenges posed by rough seas, ice, ship speeds, and the lack of tide gauges, ISOBatA proved the feasibility of opportunistic acoustic data collection, particularly in the Ross Sea. This was achieved by utilizing downtime during mooring maintenance, support for supply vessels, medical evacuation (MEDEVAC), and sheltering during standby weather conditions.

Onboard data sharing fostered valuable collaborations with other research teams, enhancing the overall scientific results. We acknowledge the MORSEA project for providing real-time of XBT and CTD data, which enabled the application of accurate sound velocity profiles.

We also thank to the PNRA Program for funding and support, to ISOBatA project partners: OGS (PI D. Accettella, P. Diviacco), UniMIB (A. Savini), IGAG-CNR (M. Cuffaro), and INGV (F. Muccini), as well as the Laura Bassi research teams for their scientific contributions and collaborations.

Keywords: Southern Ocean, Bathymetry, ISOBatA, Laura Bassi, Antarctica, IBCSO.