Ammonia in the summer Arctic marine boundary layer: Sources, Sinks and Implications

• Main Authors: Wentworth, Greg R., Murphy, Jennifer G., Croft, Betty, Martin, Randall, Pierce, Jeffrey R., Tremblay, Jean-Éric, Courchesne, Isabelle, Côté, Jean-Sébastien, Gagnon, Jonathan, Levasseur, Maurice, Thomas, Jennie L., Abbatt, Jonathan P. D.
• Other Authors: Department of Chemistry University of Toronto, University of Toronto, Department of Physics and Atmospheric Science Halifax, Dalhousie University Halifax, Department of Atmospheric Science Fort Collins, Colorado State University Fort Collins (CSU), Department of Biology Québec, Université Laval Québec (ULaval), TROPO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2015
• Subjects: [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]; Arctic; Arctic Ocean; Baffin Bay; Canadian Arctic Archipelago; Guano; Arctic Archipelago; Baffin
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-01246977

International audience The abundance of NH 3 can influence new particle formation rates, aerosol chemical and optical properties, as well as N-sensitive ecosystems via deposition. Sources and sinks of gas-phase ammonia (NH 3 ) are poorly constrained in the High Arctic due to a lack of field observations. In particular, both the magnitude and direction of sea-air NH 3 exchange are highly uncertain, although previous studies suggest the open ocean is likely to act as a net sink at high latitudes.In order to investigate potential NH 3 sources, sinks and impacts, hourly gas-phase NH 3 and particulate-phase NH 4 + and SO 4 2- measurements were taken from 13 July to 7 August 2014 aboard a research cruise throughout Baffin Bay and the eastern Canadian Arctic Archipelago. Simultaneous measurements of total seawater ammonium, pH and sea surface temperature were used to compute the compensation point (χ), which is the ambient NH 3 concentration at which sea-air fluxes change direction. Ambient NH 3 ranged from 30-650 ng m -3 throughout the cruise and was several orders of magnitude larger than measured χ values (0.4-10 ng m -3 ). Hence, the summertime Arctic Ocean is a strong net sink of NH 3 .GEOS-Chem (a chemical transport model) was employed to examine the impact of seabird guano (feces) on surface NH 3 concentrations. A simulation without guano-derived NH3 emissions yielded highly acidic aerosol and underestimated surface NH3 by several orders of magnitude. Including NH 3 emission estimates from seabird guano greatly improved model-measurement comparison. The importance of seabird guano as an NH3 source was also investigated using the FLEXible PARTicle dispersion model driven by WRF meteorology (FLEXPART-WRF). FLEXPART-WRF results confirm that air masses with origins co-located with large seabird colonies were enriched in NH 3 , whereas those originating over the open ocean were depleted in NH 3 . The influence of NH 3 from wildfires, as well as implications for N-deposition and aerosol neutralization are also ...