Currents and convection cause enhanced gas exchange in the ice–water boundary layer

laboratory study that demonstrate how shear and convection in the ice–ocean boundary layer can lead to significant gas exchange. In the absence of wind, water currents beneath the ice of 0.23 m s⁻¹ produced a gas transfer velocity (k) of 2.8 m d⁻¹, equivalent to k produced by a wind speed of 7 m s⁻¹ over the open ocean. Convection caused by air–sea heat exchange also increased k of as much as 131 % compared to k produced by current shear alone. When wind and currents were combined, k increased, up to 7.6 m d⁻¹, greater than k produced by wind or currents alone, but gas exchange forcing by wind produced mixed results in these experiments. As an aggregate, these experiments indicate that using a wind speed parametrisation to estimate k in the sea ice zone may underestimate k by ca. 50 % for wind speeds <8 m s⁻¹.