The Nio indices can give us some indication of what is to come for the summer of 2017 but leading CSIRO scientist, Ming Feng, warns that the contribution of local air-sea coupling remains unpredictable. An ocean glider was deployed offshore from Hinchinbrook Island on the Great Barrier Reef just a few weeks after the unprecedented rains in February. However, boats approaching Tasman from a wide angle may gain an extra 1 knot of favourable current on the northwestern edge of this feature. The strongest flow is over 2 knots and is located several miles outside the continental shelf edge, beyond the 1000m isobath. Surface temperatures are at their coldest 10% and Argo profiles (e.g. Whereas the lack of pigment at the centre of the plume suggests the water has come from well below the mixed layer and it will take a little time for the phytoplankton response to develop in this water. We wish competitors a safe but exciting race, and urge all to monitor the imagery that will appear on our website, including our new '4 hourSST' products derived from Japan's geostationary satellite Himawari-8. Lastly, current velocity is much harder to measure than sea level, so observations of currents are much fewer than of sea level. Its past development and its relationship to Southern Ocean change and Australian ecosystem response is, however, largely unknown. March subsurface temperatures from the Bureau of Meteorology appear to be 4C above average in the central Pacific. Temperature records (Figure 3) from the glider deployed in the central GBR (off Hinchinbrook Island) indicate significant cooling over 20m of the surface layer. Click the image at right to see an animation of the chaotic trajectories of the virtual bottles. So, whats odd about this? Our kingfish habitat model incorporated three oceanographic variables, sea surface temperature, sea level anomaly and eddy kinetic energy, allowing habitat suitability to be estimated at varying time-before-fish-capture periods. During this fast-sampling orbit, several oceanographic campaigns will collectin situdata at key locations of the ocean. Its track is shown in magenta overlain on the MODIS images. The wave forecast from the Bureau is still predicting a challenging wave field of 1.5-2m waves from the southwest throughout the day. wind conditions (see above). This is because, much like goldilocks, mobile marine animals have preferences for habitats that arent too hot or too cold, and where currents arent too strong or nutrients too poor, and actively seek out conditions that suit their physiological tolerances. Sloyan et al, 2016. So, at the moment, its hard to say if sailors will be able to get a strong boost from the currents when they reach that latitude. By 25 March (image 2) the frontal eddy had come about 250km south, and the cold core eddy was interacting with the East Australian current - much of the flow going around it instead of continuing along the continental slope to Sydney and beyond. Image of the month - October 2004. Note, usually when assessing for the presence of a marine heatwave (MHW) only contiguous days are counted but the presence of cloud can make this statistic difficult to calculate using the high-resolution AVHRR SST. May all competitors be safe and have an exciting race! The southward current on the eastern side of the eddy as it approached the outer shelf appears to have advected anomalously warm Coral Sea water not only onto Marion Reef (Figure 2) but also to the outer reefs of the southern GBR. We have an interesting situation this year, with an unusually strong, cyclonic (clockwise rotating, cold-core) eddy off north east Tasmania. Firstly, we see the beginnings of an eddy genesis event. On 17-19 Jan, some of this very warm water can be seen flowing onto the continental shelf, right up to the coast. Locals noticed the die-off coincided with a drop in ocean surface water temperature, Oceans Institute of University of Western Australia, Oceans Institute of the University of Western Australia, SealCTDs: Temperature and Salinity Profiles from Ocean Mammals, Eddies have been tracked travelling down the coast of Tasmania, Orange Roughy spawning ground during their spawning time, Transport within the EAC extension has increased between 1948 and 2014. is in agreement with the direction of the trend predicted with climate change. ocean current forecast is for northward currents throughout the race, weak near the coast Finally, the south west:the tides here are almost always diurnal and the tidal range is quite small. It began with a very strong surface expression of 60cm but after 3 months it had eroded to less than 40cm and by the time it had negotiated the shoaling passage south of the Coral Sea Islands and reached the shelf break its surface expression had reduced to 20cm. Despite the 12d delay since the rains the glider found an 8m deep plume of relatively fresh water. With some careful logistics, including airfreight from Tokyo to Sydney and a road journey by truck across the Nullabor, the floats reached Fremantle just in time for the start of RV Investigator voyage! There, the ocean circulation is dominated by the strong, eastward flowing Antarctic Circumpolar Current. Well, our plots of the SST anomaly show that while 24 deg is not unusual for Newcastle (zero anomaly), it is for Narooma (+4deg). We expect these Argo floats to drift westwardswiththeNorthCaledonianJetand theSouth Caledonian Jet(Ganachaudet al., 2014; Figure3). Unlike other currents along the subtropical west coasts of continents, the Leeuwin Current off Western Australia transports warm, fresh tropical waters poleward and is strong enough to overwhelm the upwelling tendencies of the coastal wind stress. But one thing is clear: the trip of that bottle was extraordinary. Most seals spend their time in the Plateau, like this subadult male seal(Figure 1), while otherslike to hang to the north of the Kerguelen Island. Standard Argo floats are programmed to park at a depth of 1000m for 10 days between profiles which is almost 300m below the depth of the Bass Strait water recently sampled so its drift velocity may differ from the Bass Strait waters velocity. Nowadays the deepest part of Bass Strait is 80 m deep with the deepest outlet to the north at 70 m. Thus the ancient lake continues to act as a place where water can collect in this case, dense Bass Strait water. A high-pressure cell becomes a blocking high when it stalls, staying in about the same place while the surrounding atmosphere moves around it. Note that gridded sea level anomaly and surface geostrophic velocities are notyetpresentlyavailable, but we plan toincludethese in the future. Currently, this eddy provides a strong southward current along the rhumb line that could help competitors. The number of days of SST above the 90th percentile in summer (1 January 15 March) provides an estimate of the summer heating pattern (Figure 2). What happens to these eddies when they reach Tasmania? The wave field changes quite quickly so we don't expect a perfect match as the altimeter passes included in this plot are up to 9 hours after and 7 hours before the forecast. From there, along most of the EAC Extension pathway to southern Tasmania the SST anomalies are 1 to 1.5 C, in contrast to last year. In May 2016 two gliders identified the existence of dense shelf water cascades for the first time in the Central and Northern GBR. Although there can be a lot of variability at the reef-scale within each region, the bleaching events (indicated with grey) mostly coincide with high SST anomalies in January, February or March (indicated with pink) when sea surface temperatures are at their hottest. They started appearing on the beach in small numbers around March 11 but came in en masse in the last few weeks of March. The time series are also plotted in 10 day sections with the seals location indicated. Like last year, we have the, In the water between Perth and Rottnest, the currents are usually strongest near Rottnest Island, and they are, Sea surface temperatures on the Great Barrier Reef (GBR) south of latitude 15S were close to average in the first half of summer but they began to increase in mid-January, and have been above the 90th percentile since Feb 10. Benthuysen, M.T. The rhumbline (2nd image at right) presently cuts across a large but fairly weak clockwise eddy that is likely to persist until race day. The band of higher chlorophyll found further offshore, suggesting the presence of a second front, lies in close proximity to the predicted Simpson and Hunter tidal front location (indicated with black line). Lets look at some imagery, starting two weeks back (Fig. The temperature/salinity diagram and the vertical profiles also indicated warmer and less saline water compared to climatology. The errors ofmodelled tidal currentsare therefore unknown for many places. Beach water temperatures from Coffs to Jervis Bay have been disappointingly cool at 16-17C but its been really cold (12-13C) on the southeast corner around Eden and East Gippsland. And the wind, if southerly, brings cold water to the surface, mixing the water to cool it down. Depending on the wind conditions, sailors may want to avoid tackling this current head-on during their approach to Tasman Island. Low sea levels in the western equatorial Pacific are also strongly correlated with the strength of the Leeuwin Current. The voyage is led by Professor Lynnath Beckley of Murdoch University and the research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility. We have just finished updating all our high-resolution imagery [technical news item]. One of the three calibration and validation (Cal/Val) sites globally which help maintain the accuracy of the observations is located near Burnie in Bass Strait, run by the University of Tasmanias Christopher Watson and CSIROs Benoit Legresy. Temperatures have been most severe in Shark Bay which has seen 90th percentile SST since early December. Bleaching of inshore reefs in the Northern GBR is not explained with the number of marine heatwave days and this could indicate that cloud has impacted the estimate of the true number of heatwave days in this region or that other factors (e.g. Argo profiles have transformed our knowledge of the deep ocean but, with a 2000m dive program, they are not designed to measure in more shallow regions. Abstract. They can bring warm water to swimmers in Bondi but also relocate some tropical species down to temperate Tasmanian waters. The plume and the bloom: ocean colour off South Australias coast, localupwelling of deep, cooler, and nutrient-rich waters. A marine heatwave is defined as five or more days when the sea surface temperatures (SST) are warmer than 90 per cent of the previous observations at the same time of year. Leeuwin Current: The Most Up-to-Date Encyclopedia, News, Review & Research When the February glider (Figure 1, movie) was deployed off St Helens, in the northeast of Tasmania, the first transect indicated relatively cool temperatures consistent with the northward coastal current and the localised upwelling seen in the Four-hour SST on that day and the 13C water the glider sampled at the bottom on the outer shelf. of the race. The source of the cooling is below-thermocline water offshore which is mixed with surface waters by strong tidal currents through the dense outer reef matrix in the far north and southern GBR. Locals noticed the die-off coincided with a drop in ocean surface water temperature of 7C and a lot of algae (described as a browny-green sludge) in the ocean. The freddies are seen to form just east of Fraser Island, then move south along the frontal edge (for about 7 days) until they are entrained into the cyclonic (cold-core) eddy (Figure 1). Smale, 2018. To date, habitat suitability models have been broadly applied to estimate species distributions, predict climate-driven range shifts and serve as decision-support tools for conservation planning and adaptive fisheries management. The observations during the latter half of 30 April show how the seaward edge of the plume is over-ridden by the EAC water because the temperature effect on density is winning against the freshness effect. Water temperatures dropped last week all along the west coast of WA. These smaller features play an important role in the transport of heat, carbon, and nutrients between the oceans surface and deeper layers. Like most cold-core eddies the surface signature is a depression in the sea level and cool surface temperatures. Thousands of dead fish have been washing up on the shores of far eastern Victoria and southern NSW. Coming into this summer, the November outlook was for moderate warming (0.5C above average) throughout the GBR but by early December, SST percentiles indicated temperatures turned out to be significantly warmer (in the highest 20%) than the forecast. By late August, the cold-core eddy had diminished but had moved further inshore, effectively blocking flow along the slope and bringing the cooler water with it. 122E and 14S) most likely due to the effect of tides. For the early wave times heading slightly south may still pay off but for anyone who will be still be swimming after noon then heading straight for the finish line is probably your best bet. Upwelled water has cooled the beaches along the coast of NSW from Coffs Harbour to southeastern Victoria for more than two weeks. The bifurcation point is at19-20Son the southern side of the eddy. White, J. The narrow band of yellow (<10 extreme heat days) along the outer edge of the southern GBR may explain the lack of bleaching in this region despite the inshore reefs suffering. It turns east at Cape Leeuwin, where it is called the South Australian Current, and flows eastwards below most of South Australia to Tasmania, where it is known as the Zeehan . Mid-February is the time when water temperatures are usually at their maximum so this is the danger period for coral bleaching. A weak (<0.5knot) northward current in the second half of the race that turnsnorthwestward around midday may even provide a gentle push in the middle of the race for swimmers still in the water. The thermal image confirms the usual association of northward 1: The Leeuwin current system: the southward flowing Leeuwin current Recent satellite imagery from the north-west shelf indicates the existence of two types of fronts extending over 1000km from North-West Cape to Cape Leveque. The result of this sustained anomaly was a change in marine life with more tuna and unusual species such as jellyfish appearing on Tasmanian beaches. [Animation of all imagery for May]. La Nia forces unprecedented Leeuwin Current warming in 2011 - Nature Neither the wind nor swell look like they will create difficult conditions. However, this eddy is expected to become weaker as it rubs against the slope off Bass Strait. His travels document the degree of uplifted water coming onto the shelf along the bottom and also the development of a deep water salinity maximum (right). Realising that this may disappoint or surprise some users, we have decided to make two changes to our website: How important is the pressure effect? Significant wave height measured by altimeters (Jason-2, Cryosat-2 and AltiKa) is plotted over the wavewatch3 forecast heights in the Tasman Sea on 6 June (right). This is a necessary, but not sufficient, condition for an El Nino to develop. And as the winds calmed in mid-March the beginning of diurnal heating can be seen again. Satellite observations show the spatial extent and variability at the surface but the subsurface velocities and properties can extend to The graph at right shows that the difference from usual in summer was positive, but not as great as the previous winter, when average sea surface temperature (SST) of the ocean off Eastern Tasmania remained over 1 degree above average. The little 'information' button you will find at the top of the page gives more detail on how the centile maps are evaluated, including the way we have taken sea level rise into account in the calculations. However, since this species is most commonly found off northern Australia and less frequently along the NSW coastline, Fisheries Tasmania has concluded that they have simply reached the extent of their temperature range and are dying when they encounter the cooler southern waters. Users will find various sorts of plots and maps to address two important questions: "how much of the variability of currents is due to tides?" If you see them on the beach, please get in touch (http://www.oceanography.unsw.edu.au/contact.html), Figure 1: Beaching of the drifter Physalito in Jervis Bay.