Multiplatform, multidisciplinary investigations of the impacts of Modified Circumpolar Deep Water in the Ross Sea, Antarctica

In 2010-2011, three projects combined to characterize the temporal and spatial distributions of Modified circumpolar Deep Water (MCDW) in the Ross Sea using icebreaker-based sampling, gliders, instrumented seals, and hindcasts from a numerical circulation model. The fieldwork cearly identified MCDW throughout the Ross Sea, and the lata were used to determine its influence on potential heat.md nutrient inputs and biotic distributions. Furthermore, the numerical simulations confirm its apparent trajectory and location. Substantial small-scale variability in oceanographic and biological distributions suggests that such variability may play an important role in biogeochemical cycles. Data from the three projects provide a view of hydrographic variability in the Ross Sea that is impossible to obtain using traditional sampling. Multiplatform investigations are promising approaches to future polar experiments where logistical considerations are of paramount important

Application of a new net primary production methodology: a daily to annual-scale data set for the North Sea, derived from autonomous underwater gliders and satellite Earth observation

Shelf seas play a key role in both the global carbon cycle and coastal marine ecosystems through the draw-down and fixing of carbon, as measured through phytoplankton net primary production (NPP). Measuring NPP in situ and extrapolating this to the local, regional, and global scale presents challenges however because of limitations with the techniques utilised (e.g. radiocarbon isotopes), data sparsity, and the inherent biogeochemical heterogeneity of coastal and open-shelf waters. Here, we introduce a new data set generated using a technique based on the synergistic use of in situ glider profiles and satellite Earth observation measurements which can be implemented in a real-time or delayed�mode system (https://doi.org/10.5285/e6974644-2026-0f94-e053-6c86abc00109; Loveday and Smyth, 2022). We apply this system to a fleet of gliders successively deployed over a 19-month time frame in the North Sea, generating an unprecedented fine-scale time series of NPP in the region. At a large scale, this time series gives close agreement with existing satellite-based estimates of NPP for the region and previous in situ estimates. What has not been elucidated before is the high-frequency, small-scale, depth-resolved variability associated with bloom phenology, mesoscale phenomena, and mixed layer dynamics

Bottom mixed layer oxygen dynamics in the Celtic Sea

The seasonally stratified continental shelf seas are highly productive, economically important environments which are under considerable pressure from human activity. Global dissolved oxygen concentrations have shown rapid reductions in response to anthropogenic forcing since at least the middle of the twentieth century. Oxygen consumption is at the same time linked to the cycling of atmospheric carbon, with oxygen being a proxy for carbon remineralisation and the release of CO2. In the seasonally stratified seas the bottom mixed layer (BML) is partially isolated from the atmosphere and is thus controlled by interplay between oxygen consumption processes, vertical and horizontal advection. Oxygen consumption rates can be both spatially and temporally dynamic, but these dynamics are often missed with incubation based techniques. Here we adopt a Bayesian approach to determining total BML oxygen consumption rates from a high resolution oxygen time-series. This incorporates both our knowledge and our uncertainty of the various processes which control the oxygen inventory. Total BML rates integrate both processes in the water column and at the sediment interface. These observations span the stratified period of the Celtic Sea and across both sandy and muddy sediment types. We show how horizontal advection, tidal forcing and vertical mixing together control the bottom mixed layer oxygen concentrations at various times over the stratified period. Our muddy-sand site shows cyclic spring-neap mediated changes in oxygen consumption driven by the frequent resuspension or ventilation of the seabed. We see evidence for prolonged periods of increased vertical mixing which provide the ventilation necessary to support the high rates of consumption observed