Knowledge of shallow-water bathymetry is crucial for safe and efficient marine shipping and infrastructure development. This is especially true in Nunavut, where most communities are coastal and economic activity, including community resupply and resource development, relies heavily on maritime transportation. Nearshore activity in Nunavut is set to increase, with both increased maritime traffic to and through Nunavut waters, and several major infrastructure developments (e.g. the deep water port in Iqaluit). However, most of Nunavut’s shallow waters remain poorly surveyed, and resources for new surveys are extremely limited within the Canadian Hydrographic Service (CHS). It is therefore crucial to develop innovative technologies that can be deployed rapidly and at minimal cost to provide bathymetric information for Nunavut’s shallow waters.
In ‘optically shallow waters’, where the seafloor is visible from space, bathymetry can be derived from interpretation of ocean colour as shown on satellite imagery, typically with sub-meter accuracy, to a depth determined by water clarity. Nunavut’s naturally clear waters, combined with the increasing availability of free or low-cost satellite imagery, makes it possible to provide estimates of water depth directly on the basis of satellite data acquired during the ice-free period, a process typically known as satellite-derived bathymetry (SDB). The accuracy of the derived bathymetry depends on several factors, including primarily water clarity, seafloor brightness, favourable sun-sensor geometry, and good environmental conditions such as calm seas and weak winds.
To assess the large-scale potential for SDB in Nunavut, and thus to improve the knowledge of bathymetry needed for safe marine shipping and infrastructure development in its coastal areas, the proposed research will:
1) Test and evaluate two existing SDB methods for shallow waters surrounding the largest coastal communities in Nunavut.
2) Produce up-to-date maps of water depth for the optically shallow sections of those areas.
3) Identify critical areas where existing nautical charts and satellite-derived bathymetry show significant discrepancy, and where charts accordingly may need updating and navigational aids should be deployed.
Field work: To conduct this research, measurements of seafloor reflectance (a necessary input for one of the SDB methods) will be conducted in Frobisher Bay, using SCUBA equipment and a water-proof spectrometer. In addition, measurements of water depth will be taken using a single-beam echo-sounder and a differential GPS mounted to a small boat for the shallowest parts of the bay. Additional water depth data will be acquired for free from the Canadian Hydrographic Service, and supplemented with freely available data from the University of New Brunswick’s Ocean Mapping Group.
Lab work: In the computing lab, SDB methods will be used to produce bathymetric maps by combining field data and satellite imagery, and the accuracy of the maps will be tested against reliable acoustic data. Areas with significant differences between water depths derived from SDB and those depicted on navigational charts will be identified and highlighted for chart updating and placement of additional aids to navigation.
The expected results include 1) much expanded information on shallow-water bathymetry around the seven largest coastal communities in Nunavut, as well as 2) improved knowledge concerning the applicability of SDB in Nunavut, answering such questions as where and when it is most effective, and what imagery and which techniques produce the best results. This improved knowledge can be used to further expand the use of SDB in Nunavut waters in future work.