Publication Date:
2019-07-17
Description:
During the ARK XXV 1+2 expedition in the Arctic Ocean carried out in June–July 2010
aboard the R/V Polarstern, we measured carbon monoxide (CO), non-methane hydrocarbons
(NMHC) and phytoplankton pigments at the sea surface and down to a depth
5 of 100m. The CO and NMHC sea-surface concentrations were highly variable; CO,
propene and isoprene levels ranged from 0.6 to 17.5 nmol l−1, 1 to 322 pmol l−1 and
1 to 541 pmol l−1, respectively. The CO and alkene concentrations were enhanced in
polar waters off of Greenland, which were more stratified because of ice melting and
richer in chromophoric dissolved organic matter (CDOM) than typical North Atlantic
10 waters. The spatial distribution of the surface concentrations of CO was consistent with
our current understanding of CO-induced UV photo-production in the sea. The vertical
distributions of the CO and alkenes followed the trend of light penetration, with
the concentrations displaying a relatively regular exponential decrease down to nonmeasurable
values below 50 m. However, no diurnal variations of CO or alkene con15
centrations were observed in the stratified and irradiated surface layers. This finding
suggests that the production and removal processes of CO and alkenes were tightly
coupled. We tentatively determined a first-order rate constant for the microbial consumption
of CO of 0.5 d−1, which is in agreement with previous studies. On several
occasions, we observed the existence of subsurface CO maxima at the level of the
20 deep chlorophyll maximum. This finding represents field evidence for the existence of
a non-photochemical CO production pathway, most likely of phytoplanktonic origin. The
corresponding production rates normalized to the chlorophyll content were in the range
of those estimated from laboratory experiments. In general, the vertical distributions of
isoprene followed that of the phytoplankton biomass. Hence, oceanic data support the
25 existence of biological production of CO and isoprene in the Arctic Ocean
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
notRev
Format:
application/pdf
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