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Enhanced vertical velocities associated with submesoscale motions may rapidly modify mixed layer depths and increase exchange between the mixed layer and the ocean interior. These dynamics are of particular importance in the Southern Ocean, where the ventilation of many density classes occurs. Here we present results from an observational field program in southern Drake Passage, a region preconditioned for submesoscale instability owing to its strong mesoscale eddy field, persistent fronts, strong down-front winds, and weak vertical stratification. Two gliders sampled from December 2014 through March 2015 upstream and downstream of the Shackleton Fracture Zone (SFZ). The acquired time series of mixed layer depths and buoyancy gradients enabled calculations of potential vorticity and classifications of submesoscale instabilities. The regions flanking the SFZ displayed remarkably different characteristics despite similar surface forcing. Mixed layer depths were nearly twice as deep, and horizontal buoyancy gradients were larger downstream of the SFZ. Upstream of the SFZ, submesoscale variability was confined to the edges of topographically steered fronts, whereas downstream these motions were more broadly distributed. Comparisons to a one-dimensional (1D) mixing model demonstrate the role of submesoscale instabilities in generating mixed layer variance. Numerical output from a submesoscale-resolving simulation indicates that submesoscale instabilities are crucial for correctly reproducing upper-ocean stratification. These results show that bathymetry can play a key role in generating dynamically distinct submesoscale characteristics over short spatial scales and that submesoscale motions can be locally active during summer months. [ABSTRACT FROM AUTHOR]

The Global Ocean Observing System (GOOS) is deploying a holistic system to monitor the world's ocean; however, a major challenge is many regions are chronically under-sampled. One such region is the Southern Ocean, which is remote and a harsh region to sample. The importance of improving holistic sampling in this region is clear, given its disproportionate significance to Earth and the fact that the area is exhibiting rapid change. As the Southern Ocean is beyond the capability of any single nation, the international Southern Ocean research community recognized a need for improved international coordination, strategic planning, and eventual implementation of a Southern Ocean Observing System (SOOS). The focus of SOOS is on (1) designing a sustainable system that provides data for determining the status and change of the Southern Ocean, (2) standardizing measurements across national efforts, (3) providing a forum for opportunities to guide future investments, (4) developing a portal for open transparent access to data, and (5) supporting grassroots discussion to identify/design expeditions and technology development. This manuscript highlights current SOOS strategies to meet those needs. Critical lessons emphasize the need for providing value to users who are contributing content/strategy as volunteers and sustain a dedicated office to coordinate those efforts while providing documented value to those contributing time and expertise. [ABSTRACT FROM AUTHOR]

In the Southern Ocean, there is increasing evidence that seasonal to subseasonal temporal scales, and meso- to submesoscales play an important role in understanding the sensitivity of ocean primary productivity to climate change. This drives the need for a high-resolution approach to resolving biogeochemical processes. In this study, 5.5 months of continuous, high-resolution (3 h, 2 km horizontal resolution) glider data from spring to summer in the Atlantic Subantarctic Zone is used to investigate: (i) the mechanisms that drive bloom initiation and high growth rates in the region and (ii) the seasonal evolution of water column production and respiration. Bloom initiation dates were analysed in the context of upper ocean boundary layer physics highlighting sensitivities of different bloom detection methods to different environmental processes. Model results show that in early spring (September to mid-November) increased rates of net community production (NCP) are strongly affected by meso- to submesoscale features. In late spring/early summer (late-November to mid-December) seasonal shoaling of the mixed layer drives a more spatially homogenous bloom with maximum rates of NCP and chlorophyll biomass. A comparison of biomass accumulation rates with a study in the North Atlantic highlights the sensitivity of phytoplankton growth to fine-scale dynamics and emphasizes the need to sample the ocean at high resolution to accurately resolve phytoplankton phenology and improve our ability to estimate the sensitivity of the biological carbon pump to climate change. [ABSTRACT FROM AUTHOR]

Low levels of iron limit primary productivity across much of the Southern Ocean. At the basin scale, most dissolved iron is supplied to surface waters from subsurface reservoirs, because land inputs are spatially limited. Deep mixing in winter together with year-round diffusion across density surfaces, known as diapycnal diffusion, are the main physical processes that carry iron-laden subsurface waters to the surface. Here, we analyse data on dissolved iron concentrations in the top 1,000 m of the Southern Ocean, taken from all known and available cruises to date, together with hydrographic data to determine the relative importance of deep winter mixing and diapycnal diffusion to dissolved iron fluxes at the basin scale. Using information on the vertical distribution of iron we show that deep winter mixing supplies ten times more iron to the surface ocean each year, on average, than diapycnal diffusion. Biological observations from the sub-Antarctic sector suggest that following the depletion of this wintertime iron pulse, intense iron recycling sustains productivity over the subsequent spring and summer. We conclude that winter mixing and surface-water iron recycling are important drivers of temporal variations in Southern Ocean primary production. [ABSTRACT FROM AUTHOR]

The article offers the author's insights on the Southern Ocean Seasonal Cycle Experiment (SOSCEx), which is the main source of the global carbon dioxide (CO2) mitigation plans. The author says that the Southern Ocean plays an important role in the uptake of anthropogenic (CO2) and in the natural (CO2) exchange between the atmosphere and oceans. He mentions the main themes of SOSCEx including stratification dynamics, (CO2), and carbon export.