The Bonney Coast upwelling is a large seasonal upwelling system along Australian southern shelves, from Cape Jaffa (SA) to Cape Nelson (VIC), during favourable coastal winds. The Bonney Coast upwelling, with nutrient enriched water, has been recognised as a key ecological feature. During the upwelling season (Austral Summer), swarms of krill and aggregation of blue whales are frequently found in this part of continental shelf. The upwelling is also important in the life cycle of juvenile southern Bluefin tuna and benefits other marine life. The oceanographic characteristics of the Bonney Coast upwelling are well understood through marine surveys and mooring data, as well as satellite images. However, the systematic and accurate mapping and understanding of the dynamic of the upwelling system has not been conducted. This study aims to map and investigate the spatial and temporal variability of the Bonney Coast upwelling using time-series of MODIS data. The data include more than 170 SST and Chlorophyll-a images (from July 2002 to Dec 2016), with a spatial resolution of ~1km. A combination of Topographic Position Index (TPI) and image segmentation techniques was used to map the spatial extent of the Bonney Coast upwelling. The Chlorophyll-a and SST signatures of the upwelling areas have also been extracted. The results confirmed that the Bonney Coast upwelling is indeed a seasonal system occurred between November and April. The upwelling is often most intensive in February and March. There is strong inter-annual variation. For example, in the summer of 2008-09, upwelling was only identified in February 2009; while, in the summers of 2013-14 and 2015-16, the upwelling was identified in all of the six months. Whether this inter-annual variation is influenced by the ENSO events is under further investigation. During intensive upwelling events (e.g., in Feb and Mar), the upwelling influences more than 10,000 km2 surface area, with the SST anomaly more than 1oC lower than that of its surrounding areas. The upwelling areas often have mean Chlorophyll-a concentrations over 0.8 mg/m3 which is nearly double of the mean summer Chlorophyll-a concentration in Australian continental shelf. This abstract was submitted/presented to the 2017 Australian Marine Science Association Conference - AMSA (https://www.amsa.asn.au/2017-darwin)

Coast upwelling is important for marine ecosystems and economic, because of its elevated primary and secondary productivity and large fish catch. This study developed a scale-independent and semi-automatic image processing technique to map the upwelling areas along the 4500 km long south-eastern coast of Australia from 14-year monthly MODIS SST data. The results show that there is significant spatial variability in the mapped upwelling areas, month to month, season to season and year to year. There is also strong temporal (month to month, seasonal and inter-annual) variability of the upwelling characteristics in area of influence, SST anomaly, chlorophyll-a concentrations and upwelling speed. This study identifies two persistent upwelling systems, the NSW system along the coast of the New South Wales and the WVIC/SA system along the coast of western Victoria and adjacent South Australia. The NSW coastal upwelling system occurs more or less continuously from austral spring to autumn. The WVIC/SA coastal upwelling system is a seasonal upwelling system occurred in the austral summer. The NSW coastal upwelling system has a stronger upwelling intensity than the WVIC/SA system, in terms of area of influence, SST anomaly, chlorophyll-a concentrations and upwelling speed. We believe that the NSW coastal upwelling system, especially the northern and central parts, is mainly driven by the EAC and its eddies; while, the WVIC/SA coastal upwelling is a typical wind-driven system. In addition, the results indicate that the ENSO events are likely to have a moderate impact on both the NSW and the WVIC/SA coastal upwelling systems. The El Nino (La Nina) events tend to strength (weaken) upwelling intensity. <b>Citation:</b> Zhi Huang, Xiao Hua Wang, Mapping the spatial and temporal variability of the upwelling systems of the Australian south-eastern coast using 14-year of MODIS data, <i>Remote Sensing of Environment</i>, Volume 227, 2019, Pages 90-109, ISSN 0034-4257, https://doi.org/10.1016/j.rse.2019.04.002