The annual cycle of gross primary production, net community production, and export efficiency across the North Pacific Ocean

Abstract

We measured triple oxygen isotopes and oxygen/argon dissolved gas ratios as nonincubation-based geochemical tracers of gross oxygen production (GOP) and net community production (NCP) on 16 container ship transects across the North Pacific from 2008 to 2012. We estimate rates and efficiency of biological carbon export throughout the full annual cycle across the North Pacific basin (35°N-50°N, 142°E-125°W) by constructing mixed layer budgets that account for physical and biological influences on these tracers. During the productive season from spring to fall, GOP and NCP are highest in the Kuroshio region west of 170°E and decrease eastward across the basin. However, deep winter mixed layers (>200 m) west of 160°W ventilatẽ 40-90% of this seasonally exported carbon, while only~10% of seasonally exported carbon east of 160°W is ventilated in winter where mixed layers are <120 m. As a result, despite higher annual GOP in the west than the east, the annual carbon export (sequestration) rate and efficiency decrease westward across the basin from export of 2.3 ± 0.3 mol C m À2 yr À1 east of 160°W to 0.5 ± 0.7 mol C m À2 yr À1 west of 170°E. Existing productivity rate estimates from time series stations are consistent with our regional productivity rate estimates in the eastern but not western North Pacific. These results highlight the need to estimate productivity rates over broad spatial areas and throughout the full annual cycle including during winter ventilation in order to accurately estimate the rate and efficiency of carbon sequestration via the ocean's biological pump.

Impact of recently upwelled water on productivity investigated using in situ and incubation‐based methods in Monterey Bay

“…Due to the spatial variability in , we were not able to determine the rate of change in Δ( /Ar) with time, which is needed for a nonsteady state calculation of NOP (equation ) [ Hamme et al ., ; Tortell et al ., ; Wilson et al ., ; Palevsky et al ., ]. For example, we can calculate a linear regression of Δ( /Ar) versus time over any 48 h period in Phase 2 (beginning 30 September 10:10 or later), with the 48 h period chosen to prevent diurnal cycling in from biasing the slope [ Hamme et al ., ].…”

Interannual variability in net community production at the Western Antarctic Peninsula region (1997–2014)

“…For example, the assumption of steady state may be violated during vigorous blooms in the early growing season (Figure ). Previous studies also observed strong seasonality in the NCP [ Bushinsky and Emerson , ; Emerson , ; Fassbender et al ., ; Ostle et al ., ; Palevsky et al ., ]. Net heterotrophy and entrainment of newly exported production back into the mixed layer, more commonly observed in the fall and winter [ Bushinsky and Emerson , ; Emerson , ; Fassbender et al ., ; Kortzinger et al ., ; Ostle et al ., ; Palevsky et al ., ], are not captured by our current algorithms.…”

Insight into chemical, biological, and physical processes in coastal waters from dissolved oxygen and inert gas tracers

“…Due to the spatial variability in O 2 , we are not able to determine the rate of change in ∆(O 2 /Ar) with time, which is needed for a non-steady state calculation of NOP (Hamme et al, 2012;Tortell et al, 2014;Wilson et al, 2015;Palevsky et al, 2016a). For example, we can calculate a linear regression of ∆(O 2 /Ar) versus time over any 48 h period in Phase 2 (beginning 30 September 10:10 or later), with the 48 h period chosen to prevent diurnal cycling in O 2 from biasing the slope (Hamme et al, 2012).…”