This project will collect high-quality, bio-optical, and biogeochemical data for validation of advanced satellite products from PACE OCI for the Arabian Sea, a highly under-sampled region of the worlds oceans, now experiencing dramatic ecosystem changes from human activities and climate-change. Over the past two decades, the base of the food chain of this monsoonal-driven ecosystem has transitioned from diatoms to one dominated by the mixotrophic dinoflagellate, Noctiluca scintillans (Noctiluca) that forms intense and widespread blooms visible from space. Capturing such phytoplankton transitions has been the pursuit of ocean color missions for more than three decades, and with its hyperspectral capabilities, NASAs PACE mission can now provide unprecedented insight into the response of phytoplankton communities to global pressures. Despite the dramatic rates at which the Arabian Sea has been changing, it remains among the most optically under-sampled of global water bodies. As part of this effort, we will leverage our long-standing ties with colleagues in India to collect high quality, high resolution (sub-pixel scale), continuous, underway and discrete bio-optical measurements to validate standard and advanced ocean products from PACE, essential to advance our understanding of vulnerable marine ecosystems and their response to anthropogenic change. As part of this activity, we plan to participate in one pre-monsoon cruise (2025) led by Space Applications Centre, ISRO, India, and two post-bloom ONR led cruises in April-May of 2024 and in April-May 2025. The pre-monsoon cruises are being undertaken as part of an Indo-US study focused on establishing triggers of the southwest monsoon rainfall season over the Indian sub-continent. Some of the data shared under this DOI is part of the Arabian Sea Marine environment through Science and Advanced Training (EKAMSAT) collaborative effort between the Ministry of Earth Sciences, Govt. of India and the Office of Naval Research. EKAMSAT commenced with a pilot study in June 2023. The pilot data is being archived under the SeaBASS experiment EKAMSAT_Pilot_ASTRAL (DOI: 10.5067/SeaBASS/EKAMSAT_Pilot_ASTRAL/DATA001) and can downloaded here: https://seabass.gsfc.nasa.gov/experiment/EKAMSAT_Pilot_ASTRAL.

The purpose of the BOUSSOLE project is to establish a time series of optical properties in oceanic waters, in support to bio-optics research, to calibration of ocean color satellite observations, and to validation of the products derived from these observations. The bio-optics research as well as the match-up analyses and vicarious calibration experiments are performed based on the data set that is being built from the permanent marine optical buoy and monthly cruises. The site where the mooring is deployed and where the cruises are carried out is located in the Ligurian sea, one of the sub-basins of the Western Mediterranean sea. BOUSSOLE is a joint effort by multiple organizations and is funded and supported by the following agencies and academic or governmental institutes European Space Agency (ESA), Centre National d'Etudes Spatiales (CNES), Centre National de la Recherche Scientifique (CNRS), Institut National des Sciences de l'Univers (INSU), National Aeronautics and Space Administration (NASA), University Pierre et Marie Curie (UPMC), and Observatoire Oceanologique de Villefranche-sur-Mer.

Measurements made during the BIOSOPE: Biogeochemistry and Optics South Pacific Experiment in 2004.

Measurements made in the southwest Atlantic Ocean spanning 1995 to 2004.

Measurements from the Atlantic Ocean made by the University of Maryland between New England, Bermuda, and Brazil in 2003.

Measurements made near Spain and Portugal under the AOPEX program.

Measurements taken under the Marine Optical Characterization Experiment between 1992 and 1999 off the US and Mexican Pacific coasts and central Pacific Ocean.