Hurricane Arthur and its effect on the short-term variability of <i>p</i>CO<sub>2</sub> on the Scotian Shelf, NW Atlantic

Abstract

Abstract. The understanding of the seasonal variability of carbon cycling on the Scotian Shelf in the NW Atlantic Ocean has improved in recent years; however, very little information is available regarding its short-term variability. In order to shed light on this aspect of carbon cycling on the Scotian Shelf we investigate the effects of Hurricane Arthur, which passed the region on 5 July 2014. The hurricane caused a substantial decline in the surface water partial pressure of CO 2 (pCO 2 ), even though the Scotian Shelf possesses CO 2 -rich deep waters. High-temporal-resolution data of moored autonomous instruments demonstrate that there is a distinct layer of relatively cold water with low dissolved inorganic carbon (DIC) slightly above the thermocline, presumably due to a sustained population of phytoplankton. Strong storm-related wind mixing caused this cold intermediate layer with high phytoplankton biomass to be entrained into the surface mixed layer. At the surface, phytoplankton begin to grow more rapidly due to increased light. The combination of growth and the mixing of low DIC water led to a short-term reduction in the partial pressure of CO 2 until wind speeds relaxed and allowed for the restratification of the upper water column. These hurricane-related processes caused a (net) CO 2 uptake by the Scotian Shelf region that is comparable to the spring bloom, thus exerting a major impact on the annual CO 2 flux budget.

A modeling study of temporal and spatial <i>p</i>CO<sub>2</sub> variability on the biologically active and temperature-dominated Scotian Shelf

“…pCO2 was estimated using an automated spectrophotometric technique (Lemay et al 2018). The raw pCO2 data contained high-amplitude spikes, with increases from 400 μatm to over 1000 μatm within a few hours, which were measuring artifacts and did not represent pCO2 of surrounding water.…”

Comment on bg-2021-48

“…The buoy measured surface water (at approximately 1 m depth) temperature, conductivity, pCO2, salinity and Chl-a fluorescence every hour and was deployed from 2007 to 2014 with several gaps in data due to calibration and maintenance (see Table S1 in Supplement). pCO2 was estimated using an automated spectrophotometric technique (Lemay et al 2018). The raw pCO2 data contained high-amplitude spikes, with increases from 400 μatm to over 1000 μatm within a few hours, which were measuring artifacts and did not represent pCO2 of surrounding water.…”