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BIO Coffee Talks: January 2020
Who: Jennifer Jackson
CNC-SCOR Eastern Tour Speaker, Hakai Institute, Victoria BC
What: A tale of three fjords: A comparison of marine heatwave impacts on three British Columbia mainland coastal systems
The coastline of British Columbia (25,725 km in length) is lined by numerous fjords that were carved out by glaciers and whose bathymetry (length, maximum depth, sill depth) varies with specific geologic history. Some fjords, such as Bute, Knight, and Rivers Inlets, are still influenced by headwater glaciers whose seasonal runoff strongly influences the physical, chemical and biological properties in these inlets. In recent years, warm anomalies in the Eastern Pacific atmospheric system have led to enhanced glacial melt and a prolonged marine heatwave in subsurface coastal waters. Physical (temperature and salinity) and chemical (oxygen) profile data have been collected in these three fjords since 1951, yet this nearly 7 decade-long time series has never been examined in the context of climate change. In June 2019, all three fjords were concurrently sampled by the Raincoast Foundation's R/V Achiever (Bute and Knight Inlet) and by the Hakai Institute's small boat (Rivers Inlet). Data from these three inlets show the striking impacts of glacial melt and the 2014 to 2016 marine heatwave on the internal structure of temperature, salinity and oxygen within these fjords.
When: Friday, January 31, 2020
Where: 10am, Needler Boardroom, VS-427, Bedford Institute of Oceanography, Dartmouth, Nova Scotia
Who: John Smith
Bedford Institute of Oceanography
What: The interpretation in a climate context of synoptic tracer 129I sections across the Arctic Ocean from the 2015 German, US and Canadian GEOTRACES cruises
During the 1990s, discharges of 129I from European nuclear fuel reprocessing plants increased by an order of magnitude resulting in a large, well resolved, tracer spike whose passage through the Arctic and North Atlantic Oceans via the "Arctic Loop Current" has been followed by time series measurements over the past 25 years. This robust and rapidly changing tracer signal has been used in conjunction with other gas (e.g. CFC-11, SF6) and radionuclide tracers (e.g. 137Cs, 236U) to calculate transit time distributions (TTDs), provide time scales for biogeochmical processes and constrain water circulation and mixing time scales for a wide range of high latitude water masses. 129I levels measured over the Lomonosov, Mendeleyev and Alpha Ridges in the Arctic Ocean during GEOTRACES cruises in 2015 are 10 times higher than those measured at the same locations in 1994-96 owing to the circulation of this tracer spike and they delineate in great detail the boundary current transport of tracer-rich, Atlantic Water bathymetrically steered by the ridge systems through the central Arctic. The tracer time series analysis illustrates the strong cyclonic boundary current flow that prevailed in the Canada Basin in 1994-96 when the Arctic Oscillation (AO) Index was strongly positive and its subsequent weakening under the more anticyclonic flow regime that followed a shift in the AO to a negative phase by 2015. These results indicate that the flow of surface and intermediate Atlantic water is highly advective, but that intermediate water undergoes significant inter-annual mixing during its initial entry into the Nansen Basin, probably during its flow through the Barents Sea and Santa Anna Trough. Tracer 129I simulations determined using the applied circulation model, NAOSIM (a regional, coupled sea ice-ocean model developed at the Alfred Wegener Institute) are in good agreement with the historical 129I results, thereby lending context to the interpretation of the large scale changes in arctic circulation and their relationship to shifts in climate indices.
When: Friday, January 24, 2020
Where: 10am, Needler Boardroom, VS-427, Bedford Institute of Oceanography, Dartmouth, Nova Scotia
Who: Doug Wallace
Oceanography, Dalhousie University
What: Chemical Tracers and the Development of Understanding of Arctic Ocean Circulation
The use of chemical tracers to infer qualitative aspects of the circulation of the upper layers of the Arctic Ocean (AO) commenced with measurements of nutrients and oxygen from Drift Station Alpha and the T-3 ice island during the International Geophysical Year (1957) and advanced again in the late 1960's. More detailed insight, including into the AO's deeper circulation patterns and rates, arose from the more extensive suite of tracers measured from the early Canadian ice camps LOREX (1979) and CESAR (1983). In contrast to most other ocean basins, most of our fundamental knowledge of circulation patterns and rates in the AO developed at the same time as a diverse toolkit of chemical tracers became available. Understanding has benefitted from measurement of naturally-occurring tracers, the fallout-derived tracers from bomb-testing, anthropogenic gases and source-specific radiotracers (e.g. from waste reprocessing and nuclear accidents). I will attempt to extract lessons from this history, by comparing the inferences from early, highly-restricted sampling of multiple tracers to our present state of knowledge which is based on icebreaker-supported surveys since the late 1980's, and much more data. For comparison, I will briefly review the relative extent to which chemical tracers have guided development of numerical models of AO circulation. The varying historical motivations for this research will also be considered. On the basis of the (debatable) assumption that history is a guide to the future, some suggestions for future developments in AO tracer oceanography will be presented.
When: Friday, January 17, 2020
Where: 10am, Needler Boardroom, VS-427, Bedford Institute of Oceanography, Dartmouth, Nova Scotia
Who: Jim Abraham (1); C. Fogarty (2)
Meteorological Service of Canada (retired) (1); Canadian Hurricane Centre (2)
What: The History of Extratropical Transition in Canada: impacts, research and prediction
Just over 150 years ago, a hurricane of historic proportions impacted New England and the Canadian Maritimes. The so-called Saxby Gale was predicted by a Royal Naval Officer in London England nearly a year in advance, following his analysis of the alignment of the earth and the moon and a very large predicted tide. This storm may have been the first documented case of an extreme extra-tropical transition of a hurricane, with significant property damage and loss of life in New England from freshwater flooding, and in the Maritimes from strong winds, high waves and storm surge. In 1954, the most notable hurricane in Canada's largest city, Toronto, resulted in the loss of 81 residents and left 4000 homeless from flooding after a 200mm rainfall. Then 31 years later, Hurricane Gloria threatened to take a similar track as Hazel. A media frenzy ensued, with the Canadian public glued to Cable News, following closely the forecasts from the US National Hurricane Centre. The impacts were much less than feared, with a public perception of a blown forecast. Given the lack of a hurricane related products and services, the Government of Canada made the decision to develop it's own Canadian Hurricane Centre. This presentation will highlight the steps taken to formally develop hurricane forecast and research expertise in Canada, with a focus on the challenges related to extratropical transition. Observation research included perhaps the first dedicated series of aircraft investigations into extratropical transitioning storms using a Convair 580 research aircraft. Forecast research efforts included a focus on numerical weather prediction. Ultimately, within the auspices of the WMO Tropical Research Program, the joint effort of scientists and forecasters from the international community has helped advance the understanding and prediction capability of the Canadian Hurricane Centre such that it is recognized globally for its leadership in Extratropical Transition.
When: Friday, January 10, 2020
Where: 10am, Needler Boardroom, VS-427, Bedford Institute of Oceanography, Dartmouth, Nova Scotia
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