“…Noting the significance of surface buoyancy gradients (a fact missed in the aforementioned first baroclinic mode framework), it has been suggested that surface QG (SQG) dynamics (Blumen, 1978;Held et al, 1995;Lapeyre, 2017) is a more appropriate framework for the oceans' surface Lapeyre & Klein, 2006;Sasaki & Klein, 2012), and is reflected in the altimeter measurements (Lapeyre, 2009). Though the variance of buoyancy is transferred downscale (Pierrehumbert et al, 1994;Sukhatme & Pierrehumbert, 2002), even in the presence of an ambient buoyancy gradient (Sukhatme & Smith, 2009), surface KE actually flows upscale in SQG dynamics (Capet et al, 2008a;Smith et al, 2002), consistent with the flux calculations using altimetry data. Recognizing the importance of both these approaches, there are ongoing efforts to represent the variability of the ocean surface and interpret the altimetry data in terms of a combination of interior and surface QG modes (Lapeyre, 2009;Scott & Furnival, 2012;Smith & Vanneste, 2013).…”