Relationships linking satellite-retrieved ocean color data with atmospheric components in the Arctic

Abstract. We examined the relationships linking atmospheric in-situ data of gas phase methane sulfonic acid (CH₃SO₃H, MSA), sulfuric acid (H₂SO₄, SA), iodic acid (HIO₃), highly oxidized organic molecules (HOM) and aerosol particle concentrations in the size ranges of 10‒50 nm and 100‒450 nm with satellite-derived chlorophyll a (Chl-a) and oceanic primary production (PP) during two time spans – the phytoplankton early bloom period, April‒May 2017 (30 March‒1 June, springtime) and phytoplankton late bloom; June‒July 2017 (2 June‒4 August, summertime) – in two ocean domains; Greenland Sea and Barents Sea. Atmospheric data were collected at Ny-Ålesund site in Svalbard, Norway. In general, Chl-a and PP in the Barents Sea were higher than in the Greenland Sea during the April‒May period, whereas the Greenland Sea had higher Chl-a and PP during June‒July. Phytoplankton bloom started by the loss of sea ice coverage in the Barents Sea at the marginal ice zone (MIZ) during April‒May, and in the Greenland Sea close to Svalbard Island during June‒July.

From the April‒May period to the June‒July period, the correlation between the ocean color data (Chl-a and PP) and MSA decreased in the Barents Sea and increased in the Greenland Sea, which establishes a direct relationship between the sea ice melting, phytoplankton bloom and atmospheric vapour composition. Both MSA and SA concentrations increased strongly during the bloom period, suggesting marine phytoplankton metabolism and resulting dimethyl sulphide (DMS) as the primary source of both MSA and SA in the Arctic atmosphere during spring–summer time. The highest correlation among all the atmospheric components and ocean color properties was observed between HIO₃ and Chl-a in both ocean domains during the springtime, but this feature may be connected to processes associated with the melting of sea ice. HOMs showed a low correlation with Chl-a and PP in comparison to other atmospheric vapours. The plausible explanation for such low correlation is that the primary source of volatile organic compounds (VOC) – precursors of HOM – is the soil or terrestrial vegetation of Svalbard archipelago rather than the ocean.

In springtime, small-particles (10‒50 nm) correlated strongly with Chl-a in the Barents Sea and with PP in both oceanic domains, suggesting that biogenic productivity has a strong impact on new particle formation (NPF) in the springtime. In the summertime, small-particle concentrations showed almost no correlation with biogenic parameters, indicating that compounds not connected with phytoplankton metabolism, such as HOMs, have a critical role in summertime NPF. Larger particles (100‒450 nm) showed an anti-correlation with Chl-a and PP in springtime, probably due to dilution of anthropogenic air pollution (arctic haze) during spring. In the end of the Arctic haze period in April, particle-phase SA (non-sea-salt sulphate, nss-SO₄^-2) and particle phase MSA (MS-) showed almost no correlation, whereas a connection between the gas phase MSA and SA concentrations was found. The likely reason for this is the same origin for gas phase MSA and SA (DMS oxidation), whereas SA in particle phase mostly originated from a long-distance continental source.