Fast acidification conveyed by the Gulf Stream to the North Atlantic

Abstract

<p>Since 1750s human industrial activities have emitted large amounts of CO<sub>2</sub> into the atmosphere, increasing the atmospheric CO<sub>2</sub> content to unprecedent levels. About a quarter of this exccess of carbon (namely anthropogenic carbon, C<sub>ant</sub>) is absorbed by the ocean, which acts as a major net C<sub>ant</sub> sink. Changes in the inorganic carbon chemistry of sea water due to the invasion of C<sub>ant</sub> - increasing (decreasing) concentration of hydrogen ions, H<sup>+</sup> (carbonate ions, CO<sub>3</sub><sup>2−</sup>) - are referred to as ocean acidification (OA). The North Atlantic is the oceanic region with the highest storage of C<sub>ant </sub>per area, closely linked to the Atlantic meridional overturning circulation and subpolar winter deep convection. As a result, it is also the main region where both upper-ocean C<sub>ant</sub> and fast OA signals are tranferred to deeper levels. Yet, it is still uncertain how much of this signal originates (locally) at these high latitudes or is conveyed (remotely) from the subtropics; or what are the driving mechanisms regulating its lateral vs vertical transfer at different temporal scales. Here we present the preliminary data and results of the CARING (Carbon irrigation in the Noth Atlantic by the gulf Stream) project to <em>i)</em> provide a contemporary assessment of the OA rates conveyed poleward by the Gulf Stream, and to <em>ii)</em> elucidate its role as far-field control to the North Atlantic OA. Our results of <em>i</em><em>n situ</em> pH data over the first 2000 dbar of the water-column, in combination with historical GLODAP data, show the pH decline to be the highest at the surface (subtropical waters down to</p>