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Sri Lanka, located in the northern Indian Ocean with the Arabian Sea on its western side and the Bay of Bengal on its eastern side and experiences bi-annually reversing monsoon winds. This will explore the dynamics of the surface circulation and coastal upwelling in the waters around Sri Lanka, particularly along the southern coast, using satellite imagery and numerical simulations using the Regional Ocean Modelling System (ROMS). The results confirmed the presence of the reversing current system, between the equator and Sri Lanka, in response to the changing wind field: the eastward flowing Southwest Monsoon Current (SMC) during the Southwest (SW) monsoon and the westward flowing Northeast Monsoon Current (NMC) during the Northeast (NE) monsoon, respectively. Along the eastern and western coasts, during both monsoon periods, flow is southward converging along the south coast. During the SW monsoon, along the west coast, the Island deflects the eastward flowing SMC southward whilst along the east coast the southward flow results from the Sri Lanka Dome (SLD) recirculation. SLD is formed due to SMC interation with the Island. The major upwelling region was located along the south coast due to water convergence and subsequent divergence associated with the offshore transport of water. The location of the flow convergence and hence the upwelling centre was dependent on the relative strengths of wind driven flow along the east and west coasts: during the SW (NE) monsoon the flow along the western (eastern) coast was stronger migrating the upwelling centre to the east (west).&nbsp, The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

An eruption of the Hunga Tonga-hunga Ha’apai Volcanic Eruption on 15 January 2012 caused tsunami waves, observed globally in tide gage records. In this study we investigate the origin of tsunami waves through the analysis of tide gauge records and numerical simulations in the Indo-Pacific region. The atmospheric pressure wave (Lamb wave) due the eruption was recorded in meteorological stations across Australia. The moving pressure jump was recorded as a ~6.5-hPa jump at the Norfolk Island; ~3.5 hPa at Broken Hill, NSW and Perth and was estimated to be travelling at ~340 ms–1. In the deep ocean this allows for Proudman resonance between the ocean and atmosphere generating a meteotsunami propagating westward across the Indian Ocean. Tide gauges located across the whole Indian Ocean basin recorded the meteotsunami generated by the pressure jump. There were two distinct signal on the tide gauge records. The first signal was recorded in advance of the predicted volcanic tsunami along the east coast of Australia and was due to the meteotsunami. The arrival of the second signal corresponded to tsunami wave generated by the displacement of the volcano travelling as a ‘free’ wave. These findings were confirmed by numerical simulations using an ocean circulation model that incorporated a moving atmospheric pressure jump travelling at a speed of ~ 340 ms–1. The long ocean waves were amplified due to Proudman resonance in the deep ocean, where the water was deeper than 5000 m. The model predicted of the meteotsunami corresponded well with observations., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Mesoscale eddies are common physical features in the ocean that are important for the transport of heat and momentum, and for the distribution of biochemical materials in the ocean. The existence of an anomalous, poleward flowing surface current, the Leeuwin Current (LC), drives the highest eddy kinetic energy environment among all the global eastern boundary currents off Western Australia (WA). There is a limitation in comprehensive understanding of spatial and temporal variability, in particular, the formation and vertical structure of mesoscale eddies. Therefore, this study aimed to define the climatology and vertical structure of mesoscale eddies off WA. Eddy characteristics were derived off WA (10‒40ºS, 105‒130ºE) using a vector geometry-based eddy detection algorithm applied to daily satellite altimetry data over the period 1993-2020. The vertical structure of cyclonic eddies (CE) and anti-cyclonic eddies (AE) in the Perth canyon were examined using ocean glider data over the period 2010-2017 obtained from the Australian Integrated Marine Observing System (IMOS). The seasonal and inter-annual variability and the lifecycles of mesoscale eddies were documented off WA. Shorter-lived eddy formations (, The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

In the eastern margin of the Indian Ocean, anomalous poleward-flowing Leeuwin Current (LC) interacts with the local circulation and topographic features along its path promoting instabilities and a highly energetic eddy field. Eddies play a major role on transferring physical and biogeochemical properties over a wide range of spatial and temporal scales. In particular, sub-mesoscale eddies (SME) are believed to intensify vertical fluxes and are crucial for energy transport. However, as continuous high spatial and temporal resolution data are essential for SME characterization due to their short lifespans and length scale, they are still poorly understood. Thus, this research aims to analyse the spatiotemporal variability of sub-mesoscale eddies distribution and characteristics as a response of LC dynamics along the Rottnest Continental Shelf (ROT). We applied an eddy detection and tracking algorithm to long-term (2010-2018) surface current observations obtained using High-Frequency Radar. LC interactions with the Capes Current and offshore eddies promoted zones with high horizontal shear that were linked to SME generation regions. Counter-clockwise (AC) and clockwise (C) SME were prevalent at the eastern and western boundaries of the LC, respectively, remaining close to their generation spots with 25-50h lifespans. Most of AC (C) SME were formed in August (September). AC eddies generation hotspots migrated meridionally with season, whilst C eddies were clustered in a preferential location, but migrated counter-clockwise over the seasons. The analysis of the long-time series provided detailed information of the generation and lifespans of sub-meso scale eddies and their variability in time in the study region., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)