NSFGEO-NERC: WOOD-BASED CARBON DISCHARGE TO THE ARCTIC OCEAN

Erosion processes mobilize and deliver organic carbon (OC) from soils and plants and can supply it to rivers. The resultant discharge of carbon by rivers to the world's oceans is globally significant, with current estimates of 160 Mega tonnes of carbon per year in particulate OC (POC, larger than 0.2 microns) and 200 Mega tonnes of carbon per year in dissolved OC (DOC, smaller than 0.2 microns). These estimates, however, do not account for material larger than about half a centimeter, including pieces of large wood.

Few studies have investigated the large-scale patterns of wood delivery, decay, and transport in rivers, and so we have limited knowledge of how large wood influences OC discharge to the ocean. This knowledge gap leads to our primary research goals, which are to (i) quantify annual carbon discharge in the form of large wood versus other sources of DOC and POC from the Mackenzie River drainage of Canada to the Arctic Ocean and (ii) estimate storage volume, residence time, and decay rates of large wood in the drainage basin. Our focus on the Mackenzie River is based on the fact it is the largest source of river sediment and POC to the Arctic Ocean, and anecdotally has large volumes of wood moving through its delta to the ocean, but these fluxes have not been measured.

The transformative aspects of the proposed research are: (1) quantification of proportions of OC exported as wood versus finer material from a large river, providing insight into the relative importance of different sources of OC under modern day conditions, and (2) the first assessment of the relative ages of material across the full range of particulate sizes carried by a large river from < 500 microns to large wood, providing a clearer basis for predicting how changes in the fate of coarser OC and large wood may impact the carbon cycle under a warming climate. This project will also substantially advance understanding of wood dynamics in large river basins under a warming climate that will alter wood recruitment, transport, and deposition processes, altering timing, volume, and placement of wood exports to the Mackenzie Delta and the Arctic.

Broader impacts relate to communities along the Mackenzie River and its delta are interested in the results from this study because driftwood has cultural and practical significance. They rely on wood exports as a natural resource for fuel, building, and art. Driftwood provides nutrients to ecosystems as it decays within deltaic soils. We will actively engage with the Gwich'in tribal Natural Resources Board in the Mackenzie Delta region to participate in their youth work experience programs, which pairs local high school youth to work with scientists on the land, as well as provide valuable field work training and research experience to students in the Environmental Natural Resources Training Program at Aurora Community College. We will work with northern community groups; NWT government agencies; and First Nations to facilitate community workshops and presentations to gain insight from local knowledge and to share our research. The knowledge we gain is useful as northern groups negotiate land use policies regarding incoming development proposals. Due to prior research in the area, post-doc Natalie Kramer has many personal and professional connections within the South Slave Region and Robert Hilton has connections within the Mackenzie Delta Region, thus facilitating the broader impacts from our outreach efforts.

We plan to employ local community college students in the Environmental Resources Training Program at Aurora College from the Tebacha and Aurora campuses as field assistants as well as participate in the Gwich'in renewable resources YWEP (youth work experiences) program. Aurora College serves a large population of First Nations students and is a highly valued program that trains students for employment in the North in higher-paying natural resource management jobs. The YWEP program provides youth in the Mackenzie delta region with hands-on summer research experiences in renewable resources. By working with us, the students will gain valuable field experience and become skilled at communicating with and understanding scientists. We will work closely with northern community groups, NWT government agencies, and First Nations to make the science available to them as they begin to make water management decisions about the development and use of their rivers, which are currently under pressure from international interests for massive power development projects.

We will work with the Polar Research Institute to schedule community presentations at various towns within the study region to communicate our science and to gain insight from local knowledge. Natalie Kramer already has connections within Aurora College, NWT government offices in Yellowknife, the Deh Cho First Nations in Fort Simpson at the confluence of the Liard and Mackenzie Rivers, and the Gwich'in renewable resources board in the Mackenzie delta region.