GIS Graduate Seminars: Anna Nesterovich & Abatan Akinfolarin
The spread of under-ice algal blooms in Bering and Chukchi seas as opposed to marginal ice blooms
Anna Nesterovich, GIS Certificate Candidate, Department of Geological and Atmospheric Sciences / Environmental Sciences
Advisor: Dr. Beth Caissie
The prevalence of under-ice diatom blooms in the Chukchi Sea, as opposed to the mainstream concept of marginal ice blooms as a basis for Arctic marine ecosystems, was recently postulated. The goal of my PhD project is developing a diatom-based proxy for sea ice extent in the North Pacific; it depends on the idea of marginal ice blooms as ‘savings accounts’ for benthos: marginal ice blooms are massive and the most represented in sediments, which makes it possible to reconstruct sea ice concentrations. However, if a preceding under-ice bloom depletes the nutrients in the water, the marginal ice bloom will be small and the sediments will reflect winter instead of spring ice conditions, which will affect the proxy. The problem of prevalence of those two bloom types will be a chapter in my dissertation. I will download satellite data for daily sea ice and phytoplankton concentrations in the Bering and Chukchi seas (as georeferenced TIFFs). For each pixel (25×25 km) I will extract information of chlorophyll concentrations’ changes at the ice retreat initiation and later on in the season. I will then map under-ice (a bloom never happens in open water) and marginal ice (starts after ice retreat) blooms.
A spatial detection methodology for roadway crashes around interchanges
Abatan Akinfolarin, GIS Certificate Candidate, Department of Civil, Construction and Environmental engineering
Advisor: Dr. Peter Savolainen
Crash rates are significantly elevated in the immediate vicinity of interchanges due to increases in traffic conflicts. To this end, the objective of this study is to develop a methodology to observe safety performance within the immediate vicinity of interchanges in the state of Iowa. The study involves the integration of traffic crashes (point features), volume and roadway geometry (polyline features). Buffers were created 1500 feet around each interchange in ArcGIS to select only roads that were 1500 feet from the interchange ramp terminal. In the case that interchanges were so close to each other, the problem of which interchange got the road segments attached to it up to 1500 feet was resolved by using an arc tool “create points from lines” to convert the road polylines to point features. Using the “Generate near table” tool, a near table was then created for the number of points closest to each interchange. A select by location scheme was used to associate crashes to each segment of the roadway for crashes up to 100 feet from each interchange segment. A heat map showing the high-risk areas based on crash rates on each interchange type will be created from this crash detection process.