This study presents the characterization of variability in temperature, salinity and oxygen concentration, including the vertical structure of the variability, in the upper 1000 m of the ocean over a full year in the northeast Atlantic. Continuously profiling ocean gliders with vertical resolution between 0.5 and 1 m provide more information on temporal variability throughout the water column than time series from moorings with sensors at a limited number of fixed depths. The heat, salt and dissolved oxygen content are quantified at each depth. While the near surface heat content is consistent with the net surface heat flux, heat content of the deeper layers is driven by gyre‐scale water mass changes. Below ∼150m, heat and salt content display intraseasonal variability which has not been resolved by previous studies. A mode‐1 baroclinic internal tide is detected as a peak in the power spectra of water mass properties. The depth of minimum variability is at ∼415m for both temperature and salinity, but this is a depth of high variability for oxygen concentration. The deep variability is dominated by the intermittent appearance of Mediterranean Water, which shows evidence of filamentation. Susceptibility to salt fingering occurs throughout much of the water column for much of the year. Between about 700–900 m, the water column is susceptible to diffusive layering, particularly when Mediterranean Water is present. This unique ability to resolve both high vertical and temporal variability highlights the importance of intraseasonal variability in upper ocean heat and salt content, variations that may be aliased by traditional observing techniques.
Abstract. The New Zealand subantarctic islands of Auckland and Campbell, situated between the subtropical front and the Antarctic Convergence in the Pacific sector of the Southern Ocean, provide valuable terrestrial records from a globally important climatic region. Whilst the islands show clear evidence of past glaciation, the timing and mechanisms behind Pleistocene environmental and climate changes remain uncertain. Here we present a multidisciplinary study of the islands – including marine and terrestrial geomorphological surveys, extensive analyses of sedimentary sequences, a comprehensive dating programme, and glacier flow line modelling – to investigate multiple phases of glaciation across the islands. We find evidence that the Auckland Islands hosted a small ice cap 384 000 ± 26 000 years ago (384±26 ka), most likely during Marine Isotope Stage 10, a period when the subtropical front was reportedly north of its present-day latitude by several degrees, and consistent with hemispheric-wide glacial expansion. Flow line modelling constrained by field evidence suggests a more restricted glacial period prior to the LGM that formed substantial valley glaciers on the Campbell and Auckland Islands around 72–62 ka. Despite previous interpretations that suggest the maximum glacial extent occurred in the form of valley glaciation at the Last Glacial Maximum (LGM; ∼21 ka), our combined approach suggests minimal LGM glaciation across the New Zealand subantarctic islands and that no glaciers were present during the Antarctic Cold Reversal (ACR; ∼15–13 ka). Instead, modelling implies that despite a regional mean annual air temperature depression of ∼5 ∘C during the LGM, a combination of high seasonality and low precipitation left the islands incapable of sustaining significant glaciation. We suggest that northwards expansion of winter sea ice during the LGM and subsequent ACR led to precipitation starvation across the middle to high latitudes of the Southern Ocean, resulting in restricted glaciation of the subantarctic islands.
The mismanagement of waste and subsequent presence of litter in the environment is an increasingly significant problem. Globally, rivers have been shown to be a major pathway for mismanaged waste. We investigated the distribution of macro, meso and micro litter along the Belize river basin. The North-East Atlantic OSPAR beach litter monitoring protocol was adapted for Belize, taking into account local issues such as mangroves and Sargassum sp. accumulations. On average, 77.3% of litter items consisted of plastic, and the most common items categories were unidentifiable plastic pieces (0–2.5 and 2.5–50 cm), broken glass, and metal bottle caps. The study indicated that there is an increase in the litter load as you move from catchment to coast, with both Plastic Pieces (PP) and Fishing Related (FR) items also increasing in numbers down the system. Additionally, microplastics abundance was determined in riverine sediments and in the riverine fish Cichlasoma synspilum (n = 22). All sediment samples contained microplastics, with a concentration of 200–6500 particles per kg dry sediment. Microplastics were found to be present in 36% of the riverine fish. The data from this study will provide evidence for the formation of Belizean legislation to reduce marine litter.
Abstract. The New Zealand subantarctic islands of Auckland and Campbell, situated between the Subtropical Front and the Antarctic Convergence in the Pacific sector of the Southern Ocean, provide valuable terrestrial records from a globally-important climatic region. Whilst the islands show clear evidence of past glaciation, the timing and mechanisms behind Pleistocene environmental and climate changes remain uncertain. Here we present a multidisciplinary study of the islands – including marine and terrestrial geomorphological surveys, extensive analyses of sedimentary sequences, a comprehensive dating program, and glacier flowline modelling – to investigate multiple phases of glaciation across the islands. We find evidence that the Auckland Islands hosted a small ice cap at 384,000 ± 26,000 years ago (384 ± 26 ka), most likely during Marine Isotope Stage 10, a period when the Subtropical Front was pushed northwards by seven degrees, and consistent with hemispheric-wide glacial expansion. Despite previous interpretations that suggest the maximum glacial extent occurred in the form of valley glaciation at the Last Glacial Maximum (LGM; ~ 21 ka) age, our combined approach suggests minimal LGM glaciation across the New Zealand Subantarctic Islands, and that no glaciers were present during the Antarctic Cold Reversal (ACR; ~ 15–13 ka). Instead, our flowline modelling, constrained by field evidence, implies that despite a regional mean annual air temperature depression of ~ 5 °C during the LGM, a combination of high seasonality and low precipitation left the islands incapable of sustaining significant glaciation. We suggest that northwards expansion of winter sea ice during the LGM and subsequent ACR led to precipitation starvation across the mid to high latitudes of the Southern Ocean, resulting in restricted glaciation of the subantarctic islands.
Marine litter is a significant global threat. The complex and cross cutting nature involved in tackling marine litter requires a coordinated response involving multiple sectors and a broad range of stakeholders. Small Island Developing States (SIDS) are particularly vulnerable to detrimental impacts of marine litter on quality of life and economies, particularly tourism and fisheries sectors. This paper presents national Marine Litter Action Plans (MLAP) as effective tools for coordinating responses addressing marine litter and specifically outlines the process undertaken to develop a national MLAP for the country of Belize, a Caribbean SIDS. Actions included in the MLAP, adopted by Belize in 2019, focused on developing science related to marine litter through monitoring and capacity building, tackling land- and sea-based sources through enforcement and planning, and boosting awareness through outreach and education. The paper further summarizes common challenges faced by SIDS and identifies key enabling conditions that facilitated MLAP development and adoption from perspective of a Caribbean SIDS. These experiences from Belize include stakeholder engagement, communication, governance, transparency, equity, scientific surveys, data gaps, and capacity building. The lessons learned from this practical application can be applied when developing and implementing MLAPs in other SIDS and beyond.
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