Tag: Oral Session 2 M

The effects of restoration fill elevation on carbon accumulation in Pacific Northwest estuaries

Presenter(s): Emil Sadofsky

Faculty Mentor(s): Scott Bridgham

Oral Session 2 M

Agricultural development has significantly decreased the extent of costal wetlands in the Pacific Northwest. Some previously developed wetlands have been restored, but the effects of restoration on their carbon cycling functions are still unknown. To better understand land use effects on carbon cycling, we compared soil carbon dynamics in restored and reference wetlands in the South Slough estuary in Coos Bay, Oregon. We measured soil carbon content and used radioisotope dating to calculate carbon pools and carbon accumulation rate, and we measured in situ carbon dioxide (CO2) and methane (CH4) emissions in restored and reference wetlands to better understand carbon fluxes. To compare different methods of restoration, the restored sites were originally restored to different elevations. We found that the restored wetlands will have smaller and shallower carbon pools than reference sites. We also found that carbon accumulation will be fastest in the reference marsh. Among the restored marshes, we found that carbon accumulation is fastest in the low elevation marsh and slowest in the high marsh.

Future Flood Risk in the Columbia River Basin Under Climate Change

Presenter(s): Laura Queen

Faculty Mentor(s): Hank Childs & Phil Mote

Oral Session 2 M

The Columbia River has long provided resources as a cultural, economic and ecological agent in the Pacific Northwest. People have congregated along the Columbia’s banks throughout history, from the earliest settlements to contemporary metropoles, but this close proximity poses a serious threat when extreme flooding occurs. Understanding how climate change will affect the future flood risk throughout the Columbia River Basin is imperative for risk mitigation and infrastructural planning. To address this question, we are using an ensemble data set which provides daily streamflow values (1950-2100) for 172 different future projections for 396 locations in the Columbia Basin. To run just one future projection, a modeler must make four choice decisions: the representative concentration pathway (RCP), global climate model (GCM), meteorological downscaling method (MDM), and the hydrological model setup. This ensemble dataset contains 172 projections created by a modeling decision chain containing 2 RCPS, 10 GCMs, 2 MDMs, and 4 setups. With an ensemble dataset produced by multiple hydrologic model parameterizations, we are able to diminish the influence of human-made modeling decisions and find a trend in flood risk change amongst the 172 projections. From the daily time-step streamflow data, we fit probability distributions to extreme events from each water year and estimate flood statistics for floods with 10, 20 and 30 year return periods. From this analysis, we find a substantive increase in flood risk for all outlets sites in the Columbia River Basin and are beginning to study the correlation between sub-basin snow-dominance and increased flood risk.

Quantifying upper layer ocean dynamics using iceberg GPS Tracking

Presenter(s): Richelle Ann Cabatic

Faculty Mentor(s): Kristin Schild & David Sutherland

Oral Session 2 M

The Greenland proglacial fjord system, where glaciers from the ice sheet reach the ocean, is an important contributor to sea level rise. When reaching the ocean, these glaciers break off icebergs. These icebergs travel through the fjord and out into the open ocean. All the while, different types of water circulate through the fjord, meeting with the glacier’s terminus and affecting it’s stability. The tidewater glacier, Jakobshavn Isbrae, and it’s fjord, Ilulissat, is of particular interest because it is the most prolific glacial system in Greenland in terms of ice export. Many studies have addressed Jakobshavn’s glacial front, but little is known about Ilulissat’s ocean circulation due to the difficulty of collecting field measurements in the ice-choked region. Through our study, we deploy transmitting GPS units on icebergs in Ilulissat Fjord, thereby directly tracking iceberg movement and indirectly detecting the fjord’s circulation patterns. Using icebergs as proxies for surface circulation thus provides an alternative to deploying marine instruments that have minimal likelihood for survival in the treacherous fjord environment. Results of our study show that: at a distance of 35km away from the glacier terminus, iceberg movement is no longer dominated by glacial calving events; and that there are eddy circulation patterns at fjord widening locations. This study has the potential to help oceanographers understand more about Ilulissat’s circulation dynamics, and can inform glaciologists about how glaciers such as Jakobshavn’s acceleration is affected by this type of circulation.