Who: Guoqiang Liu

What: Implications of Ocean Waves on Air-sea Interactions and Ocean Circulation

Surface waves play essential roles in ocean dynamics. They can significantly modify the air-sea interactions and therefore regulate the general circulation. In the upper ocean, surface waves enhance the turbulence level through wave breaking and Langmuir turbulence. Combining high-resolution measurements and numerical simulations, it is found that the ocean responses, especially for the thermal and dynamical current responses, are improved significantly when the surface wave effects are taken into consideration. More importantly, by modulating the momentum fluxes through the growing/decaying surface waves, the spatial-temporal near inertial currents, diapycnal mixing and deep ocean vertical transport are changed greatly. All these results indicate that surface waves should be included in ocean models, in particular, the coupled atmosphere-ocean and climate models.

When: Wednesday, April 26, 2019

Where: 10am, George Needler Boardroom, Room VS-427, van Steenburgh Building, Bedford Institute of Oceanography, Dartmouth, Nova Scotia

Who: Harald Yurk

What: Finding Ways of Reducing the Threat of Vessel Traffic on Whales and Other Marine Mammals through Detection and Avoidance

Physical disturbance of whales due to vessel traffic is growing because more vessels are on the water every year requiring more associated human activities around vessel traffic (e.g. port developments). The work of DFO Science in support of mitigating disturbance includes evaluating the effectiveness of existing and designing of new whale detection techniques for the purpose of finding whales and alerting ships. The work also focusses on the efficiency and sustainability of ship alert systems, such as where and when real-time alerts are appropriate and what alternatives are possible. While the work focusses on endangered whales such as Southern Resident Killer Whales (SRKW) in the Pacific region and North Atlantic Right Whales (NARW) in the Atlantic region the results will be applicable to all at-risk marine mammals. Further, the work will help closing knowledge gaps of the distribution of marine mammals and their movements through areas in which ship traffic poses a threat to them. In my presentation I will provide an overview of the problem (ship traffic and whales) with a focus on SRKW, broadly explain some of the detection technologies and ship alert means evaluated and provide an introduction to killer whales with a focus on their acoustic behaviour.

When: Wednesday, April 17, 2019

Where: 10am, Lewis King Boardroom, Room VG06, Vulcan Building, Bedford Institute of Oceanography, Dartmouth, Nova Scotia

Who: Jordy Thomson

What: Shifting patterns of top-down control in a rapidly changing Australian seagrass ecosystem

Shark Bay, Western Australia is home to among the world's largest contiguous seagrass meadows, and has been the site of a long-term ecological research project since 1997. Over the past two decades, we have studied the role of large predatory sharks in structuring seagrass communities via their influence on the behaviour and grazing patterns of mega- and macro-herbivores. More recently, an unprecedented marine heatwave triggered large-scale dieback of the foundation seagrass in Shark Bay, resulting in marked shifts in herbivore densities and, likely, trophic interactions. In this talk, I'll summarize what we have learned about patterns of top-down control in subtropical seagrass ecosystems with intact top predator populations, and ways in which these patterns may shift in a changing climate. Plus plenty of photos to brighten the April outlook.

When: Friday, April 12, 2019

Where: 10am, George Needler Boardroom, Room VS-427, van Steenburgh Building, Bedford Institute of Oceanography, Dartmouth, Nova Scotia

Who: Eric Oliver

What: Historical and Future Projected Changes in Marine Heatwaves Globally

Marine heatwaves are important events in oceanic systems that can have devastating consequences for ecosystems, causing ecological changes and socioeconomic losses. Prominent marine heatwaves have occurred recently and attracted scientific and public interest, but comprehensive assessments of how these events have been changing globally is missing. This talk will first review our current understanding of marine heatwaves, including how we may define and categorise them. Then, research results will be presented whereby using daily satellite observations, daily in situ measurements, and gridded monthly in situ-based sea surface temperatures significant increases in marine heatwaves over the past century are found. Future changes in marine heatwaves to the end of the 21st century are then investigated, as simulated by CMIP5 global climate model projections. It is found that, from 1925 to 2016, global averages of marine heatwave frequency and duration have increased by 34% and 17%, respectively, resulting in a 54% increase in annual marine heatwave days. Importantly, these trends can largely be explained by the increase in mean ocean temperatures, rather than a change in variability. Future projections show significant, and accelerating, increases in MHWs properties into the 21st century with many parts of the ocean reaching a near-permanent MHW state by the late 21st century, regardless of emissions scenario considered (RCP4.5, 8.5). Comparison with simulations of a natural world, without anthropogenic forcing, indicate that these trends have emerged from the range of natural variability within the first two decades of the 21st century. This implies that the climate system has departed significantly from natural marine heatwave conditions under which ecosystems evolved, and therefore impacts on marine ecosystems can be expected to be widespread, significant and persistent. Finally, a review of ongoing and future work building on the above will be presented.

When: Friday, April 5, 2019

Where: 10am, George Needler Boardroom, Room VS-427, van Steenburgh Building, Bedford Institute of Oceanography, Dartmouth, Nova Scotia