Do upwelled waters from the California Undercurrent contribute to high pCO2 within the fjord system of Nootka Sound, BC?

Abstract

[author abstract] An understanding of coastal ocean-atmosphere CO2 exchange is important for modelling future greenhouse gas scenarios. This study focuses on the fjord system of Nootka Sound in December 2015. 16 stations were sampled from 60km offshore to the head of Muchalat Inlet with the aim of evaluating the influence of nutrient rich, high pCO2 waters from the California Undercurrent on the fjord system. Samples were taken throughout the water column to obtain oxygen, nutrient and carbonate system data. Net autotrophy and high nutrient waters were observed at the mouth of the fjord system; though it was thought these waters did not originate from the California Undercurrent as isopycnals were suggestive of coastal downwelling. Deep waters in the fjord had pCO2> 1500μatm and high levels of denitrification were observed. Higher pCO2 was observed in surface water compared to the atmosphere at most stations, indicating the fjord was acting as a source of atmospheric CO2.