Measured Global OH Reactivity in the Marine Boundary Layer: Evidence for Missing OH Reactivity

Atmospheric oxidation chemistry over the world’s oceans controls the lifetime of methane and sets the background chemistry for populated land regions. While the atmosphere above the remote oceans is considered to be clean compared to that over the populated land, substantial amounts of organic matter appear to be exchanged between the ocean and the atmosphere. This organic matter likely reacts with the hydroxyl radical (OH), setting into motion more complex chemistry than is usually ascribed to such remote atmospheric regions. During the four Atmospheric Tomography (ATom) missions in 2016-2018, OH reactivity (the inverse of the OH lifetime) was measured on the NASA DC-8 aircraft. While OH reactivity was measured with an earlier version of this same instrument during a previous NASA aircraft campaign over the northern Pacific in 2009, these OH reactivity measurements over both the northern and southern Pacific and Atlantic Oceans during ATom provide an unprecedented opportunity to analyze the OH reactivity over wider regions than ever before. In this presentation, we provide evidence for missing OH reactivity over the oceans. We show that this missing OH reactivity is related to factors consistent with the emission of organic compounds from the ocean.