Collaborative Research: A High Resolution Multi-Tracer Biogeochemical Study of the Pacific Arctic

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Surface warming is occurring in the Arctic at a pace that is roughly double that of the global average, leading to reductions in extent and thickness of sea ice and prolonged seasonal periods of open water throughout much of the Arctic Ocean. Direct observations in the Pacific Arctic region, including the northern Bering and Chukchi seas, are needed to understand how this ecosystem is shifting in a time of rapid change. To that end, the investigators will participate in a research expedition scheduled for summer 2020 and will make simultaneous oceanographic measurements of dissolved oxygen, dissolved carbon dioxide, dissolved nutrients, particulate organic matter distribution and composition, and plankton productivity. In addition to providing new information about biological and physical processes in the region, these observations will complement and extend a companion project conducted by collaborators from the Woods Hole Oceanographic Institution about the distribution and activity of harmful algal bloom species in the region, which are an emergent concern for Alaskan communities. This study will support graduate and undergraduate students, providing them research and experiential educational opportunities. The investigators will attend regional meetings and seminars in Alaska to communicate their findings to broader audiences.To test hypotheses related to the controls and spatial-temporal patterns in elemental cycling and productivity of the Pacific Arctic, the investigators will measure a novel suite of ecosystem-relevant tracers, sampled at high frequency from the US Coast Guard Cutter Healy's underway system and from CTD surveys. They will make simultaneous, high resolution measurements of dissolved nitrate and phosphorous to evaluate nutrient dynamics, oxygen-argon ratios and partial pressure of carbon dioxide to determine net community production and biologically-mediated air-sea carbon dioxide exchange, and particulate organic matter concentrations and particle-optical properties (particle size, beam attenuation and chlorophyll fluorescence) to quantify trends in phytoplankton biomass and size structure. In addition, the investigators will use the triple oxygen isotope technique and carbon-13/nitrogen-15 uptake incubations to determine rates of primary productivity, as well as Fast Repetition Rate Fluorometry to evaluate phytoplankton nutritional status under variable environmental conditions. This multi-tracer approach will discriminate different processes (e.g., advection, upwelling and mixing) and their biogeochemical/ecological response (e.g., productivity, respiration, export, and shifts in community composition) at fine temporal and spatial scales.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.