Aurora

Thesis Defense: Brian Irwin, PhD in Geophysics

Thesis Title: How To Descend A Rocky Slope: Numerical Techniques For The Solution Of Noisy Optimization Problems

Date and Time: Monday, June 26th at 12:30pm

Location: Zoom

IOS Seminar: The Physical Oceanography of a Broad, Mid-latitude, Fjord. Observations, Seasonality and Wind Response of Fortune Bay (Newfoundland, Canada)

Speaker: Dr. Sebastien Donnet

Date and Time: June 21sr at 11:00am - 12:00pm

Location: Microsoft Teams meeting

Description: This seminar will review the physical environment of Fortune Bay, a mid-latitude and broad fjord located in Newfoundland, Canada. The results of 2-years of continuous observations as well as the analysis of historical records and numerical model simulations will be presented. Newly collected observations reveal the presence of coherent downwelling and upwelling signals, associated with vigorous alongshore currents, propagating cyclonically around the fjord. Along with the historical data, those observations also allow the determination of the seasonal climate of the water structure and some of its main forcing (wind, tides and freshwater runoff). The implementation of a fully non-linear, 3-dimensional, numerical model allows the identification of the main process responsible for those dominant signals as well as their origin and some of their propagation characteristics.

IOS Seminar: Simulating Biogeochemical Dynamics on the West Coast

Speaker: Jonathan Izett

Date and Time: June 23, 2023 at 11:15am - 12:15pm, participants can join starting 11:00am

Location: online or in person in the IOS Auditorium

Description: The talk will focus primarily on an overview of efforts to find an alternative (simpler) method for assimilating biogeochemical observations into ocean models. Traditional four-dimensional variational data assimilation includes the technical challenge of constructing tangent linear (TLM) and adjoint (ADJ) models corresponding to the non-linear BGC model. This hurdle can be time-consuming, particularly for non-linear BGC models experiencing active development, with regular updates to functional types or representation of key BGC processes. We evaluated two alternate approaches that greatly simplify TLM and ADJ construction and eliminate the need for code updates when the underlying, non-linear BGC model changes.  One form of model-reduced data assimilation represents BGC interactions as a linear combination of orthogonal modes, while the second approach treats BGC variables as passive tracers within the data assimilation system. An evaluation of the methods will be presented in the context of a simple nutrient-phytoplankton-zooplankton-detritus (NPZD) BGC model implemented in the Regional Ocean Modelling System (ROMS) for the U.S. west coast. Jonathan will also share a brief overview of the work he is doing at IOS as part of the team developing a coupled physical-biogeochemical model of Vancouver Island’s west coast.