On the Interplay between the Circulation in the Surface and the Intermediate Layers of the Arctic Ocean

Abstract

The circulation of the Arctic Ocean has traditionally been studied as a two-layer system, with a wind-driven anticyclonic gyre in the surface layer and a cyclonic boundary current in the Atlantic Water (AW) layer, primarily forced remotely through inflow and outflow to the basin. Here, an idealized numerical model is used to investigate the interplay between the dynamics of the two layers and to explore the response of the circulation in each of the layers to a change in the forcing in either layer. In the model, the intensity of the circulation in the surface and AW layers is primarily set by the ocean surface stress curl intensity and the inflow to the basin, respectively. Additionally, the surface layer circulation can strongly modulate the intensity of the intermediate layer by constraining the lateral extent of the AW current on the slope. In contrast, a change in the AW current strength has little effect on the surface layer circulation. The intensity of the circulation in the surface layer adjusts over a decade, on a time scale consistent with a balance between Ekman pumping and an eddy-induced volume flux toward the boundary, while the circulation in the AW layer adjusts quickly to any change of forcing (;1 month) through the propagation of boundary-trapped waves. As the two layers have different adjustment processes and time scales, and are subject to forcing that varies on all time scales, the interplay between the dynamics of the two layers is complex, and more simultaneous observations of the circulation within the two layers are required to fully understand it.

Arctic Ocean Freshwater Content and Its Decadal Memory of Sea‐Level Pressure

“…HiGEM is a fully coupled climate model based on the Hadley Centre Global Environmental Model version 1 (HadGEM1; Johns et al, 2006) with a relatively high resolution ocean and a reasonable representation of the Arctic (Lique et al, 2015(Lique et al, , 2017. HiGEM is a fully coupled climate model based on the Hadley Centre Global Environmental Model version 1 (HadGEM1; Johns et al, 2006) with a relatively high resolution ocean and a reasonable representation of the Arctic (Lique et al, 2015(Lique et al, , 2017.…”

“…In idealized models and theory, this process is arrested by baroclinic eddies; isopycnal slopes increase until eddies (resolved or parameterized) are able to bring the system into equilibrium, such that the FWC of the Beaufort Gyre is sustained by a balance between Ekman convergence and an eddy-induced volume transport towards the boundary (Davis et al, 2014;Lique et al, 2015;. After a change in surface stress, the FWC in these models comes into equilibrium on decadal timescales, determined by the eddy diffusivity.…”

The Mediterranean outflow in the Strait of Gibraltar and its connection with upstream conditions in the Alborán Sea

“…5d. Similar procedures have been followed in the literature to estimate geostrophic circulation patterns from altimetry data (Naranjo et al, 2012;Lique et al, 2015).…”

“Climate response functions” for the Arctic Ocean: a proposed coordinated modelling experiment

“…Previous coordinated experiments have compared the climate states of these models and their sensitivity to parameters and forcing fields (see, e.g., Proshutinsky et al, 2011;Ilicak et al, 2016). But one is also keenly interested in how the system responds to a change in the forcing, as in, for example, the idealized study of Lique et al (2015). This is perhaps particularly true in the Arctic, which is undergoing rapid change as the Earth warms.…”