Project Funding: 2017 - 2020

NRA: 2016 NASA: Carbon Cycle Science   

Funded by NASA

Abstract:
This research seeks to better quantify the seasonality and variability in the riverine contribution of organic carbon into Arctic Ocean coastal margins. Rivers feeding the coastal Arctic Ocean drain several types of biomes and represent a major source of particulate and dissolved organic carbon (POC and DOC) to Arctic coastal margins. Climate-driven changes to Arctic terrestrial biomes will almost certainly alter the magnitudes and relative contributions of POC and DOC that different rivers transport into their adjacent coastal oceans. Direct assessment of river-specific baselines for this terrestrial carbon input has been challenging because much of this carbon is delivered by the spring freshet that occurs while the coastal ocean is still covered by landfast sea ice. This project will examine the seasonality and magnitude of this carbon transport and its relationship to coastal hydrography and circulation, the spring freshet, seasonal ice dynamics, and remote sensing variables available during the freshet such as sea ice cover and ice morphology. This research involves a two-year observational study on the Alaskan Beaufort Shelf using bio-optical moorings and direct, through-ice monitoring to assess the magnitude and timing of riverine POC and DOC contribution into the coastal Arctic. Six moorings will be deployed near Prudhoe Bay at the mouths of two rivers that drain terrestrial biomes with different vegetation and precipitation characteristics: the Kuparuk River which drains a primarily tundra biome, and the Sagavanirktok River which drains the coastal plain and the north slope of the Brooks Range. Sensors will measure optical proxies for POC and DOC over two full annual cycles, most critically in the period encompassing the spring freshet when riverine transport of POC and DOC is largest but when these coastal waters remain ice-covered and thus not yet directly observable by remote sensing. Monthly-scale field studies will be conducted in the late spring, immediately prior to the freshet, to deploy sensor clusters through the sea ice to directly measure these optical proxies over the course of the freshet until sea ice cover degrades and coastal waters become visible to remote sensors. These two observational efforts will generate unique and valuable time series of proxies for POC and DOC as well as key environmental parameters related to coastal circulation, sea ice cover, and river discharge dynamics. These will be used in a subsequent analysis to quantify how the spatial and temporal evolution of riverine DOC and POC injection by these two rivers relate to physical factors such as riverine seasonal flow and freshwater runoff, coastal hydrography and circulation, and importantly, seasonal sea ice cover. By examining two representative rivers that drain different types of terrestrial biomes, this study will provide insight into possible source-river differences in organic carbon transport into these seasonally ice-covered Arctic coastal margins. Having such direct, long-term observations of proxies for the POC and DOC delivered by the spring freshet is essential for reducing uncertainties about key aspects of the organic carbon cycle on the Alaskan Arctic coastal margin: • What is the timing and magnitude of POC and DOC injection into Arctic coastal margins? • How can autonomous systems help to assess differences in POC-DOC contributions by rivers that drain such different types of biomes (e.g., tundra vs. alpine)? • How do ice cover, hydrography, circulation, winds, and freshwater input affect the areal distribution of water column POC and DOC on this shelf, during the freshet? • How might available remote sensing variables during this time of year be used to better understand similar riverine contributions of POC and DOC more broadly across Arctic coastal margins in the Beaufort Sea and beyond?

Publications:

Catipovic, L., Longnecker, K., Okkonen, S. R., Koestner, D., Laney, S. R. 2023. Optical Insight Into Riverine Influences on Dissolved and Particulate Organic Carbon in a Coastal Arctic Lagoon System. Journal of Geophysical Research: Oceans. 128(4). DOI: 10.1029/2022JC019453

More details may be found in the following project profile(s):

• NASA Ocean Biology & Biogeochemistry (OBB) Project Profile