Review for "Stratigraphic architecture of Solander Basin records Southern Ocean currents and subduction initiation beneath southwest New Zealand"

The opening of the Tasmanian Gateway during the Eocene and further deepening in the Oligocene is hypothesized to have reorganized ocean currents, preconditioning the Antarctic Circumpolar Current (ACC) to evolve into place. However, fundamental questions still remain on the past Southern Ocean structure. We here present reconstructions of latitudinal temperature gradients and the position of ocean frontal systems in the Australian sector of the Southern Ocean during the Oligocene. We generated new sea surface temperature (SST) and dinoflagellate cyst data from the West Tasman margin, ODP Site 1168. We compare these with other records around the Tasmanian Gateway, and with climate model simulations to analyze the paleoceanographic evolution during the Oligocene. The novel organic biomarker TEX86- SSTs from ODP Site 1168, range between 19.6 &#8211; 27.9&#176;C (&#177; 5.2&#176;C, using the linear calibration by Kim et al., 2010), supported by temperate and open ocean dinoflagellate cyst assemblages. The data compilation, including existing TEX86-based SSTs from ODP Site 1172 in the Southwest Pacific Ocean, DSDP Site 274 offshore Cape Adare, DSDP Site 269 and IODP Site U1356 offshore the Wilkes Land Margin and terrestrial temperature proxy records from the Cape Roberts Project (CRP) on the Ross Sea continental shelf, show synchronous variability in temperature&#160;evolution between&#160;Antarctic and&#160;Australian sectors of the Southern Ocean. The SST gradients are around 10&#176;C latitudinally across the Tasmanian Gateway throughout the early Oligocene, and increasing in the Late Oligocene. This increase can be explained by polar amplification/cooling, tectonic drift, strengthening of atmospheric currents and ocean currents. We suggest that the progressive cooling of Antarctica and the absence of mid-latitude cooling strengthened the westerly winds, which in turn could drive an intensification of the ACC and strengthening of Southern Ocean frontal systems.

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Spatial & Temporal Patterns of Microplastic Pollution in Wellington, New Zealand, and the Southern Ocean

10.26686/wgtn.17148608 ◽

2021 ◽

Author(s):

◽

Caitlyn Shannon

Keyword(s):

New Zealand ◽

Southern Ocean ◽

Spatial Variation ◽

Marine Environment ◽

Surface Waters ◽

Environmental Drivers ◽

Plastic Pollution ◽

Temporal And Spatial Variation ◽

Beach Sediments ◽

Temporal And Spatial

The global marine environment is currently facing unprecedented anthropomorphic change and stress. One such stressor is plastic pollution, which has continually increased in magnitude since mass production began in the 1940’s. An increase in plastic debris throughout the oceans not only results in an infiltration of the pollutants throughout the entirety of the marine environment, but also increases the risk that it impacts the physiological, structural, and behavioural traits of various organisms – including humans. These negative interactions are particularly likely with microplastic particles (< 5 mm), as they can enter and be transferred throughout the food web with ease. However, research in the field of microplastic pollution is extremely one-sided, with most present studies focusing on the Northern Hemisphere. Additionally, comparatively little has been investigated regarding temporal and spatial patterns of microplastic occurrence. The aim of this research was to 1) examine the abundance and distribution of synthetic particles in sub-surface waters of the Southern Ocean, across broad temporal and spatial scales and 2) examine finer-scale spatial and temporal patterns of microplastic load within the urbanised Wellington Harbour, New Zealand, using a combination of environmental and biological indicators. To assess the broad-scales of temporal and spatial variation in the Southern Ocean, annual Continuous Plankton Recorder (CPR) tows were undertaken between New Zealand waters and the Ross Sea, Antarctica, over a span of 9 years (the austral summers of 2009/10 – 2017/18) and a range of 5 oceanographic zones and two frontal systems, totalling a distance of approximately 22,000 km. Overall, patterns were inconsistent, with no constant increase or decrease in load throughout the years, while spatial variation was minimal and not associated with particular oceanographic fronts or proximity to an urban area. Despite no consistent spatial variation, temporal differences did occur between years. Again, there were no identifiably consistent trends across years (i.e. a gradual increase), but there was a substantial peak in 2009/10 and a trough in 2012/13. Such changes are likely due to large-scale variations in ocean circulation systems, along with environmental drivers such as El Niño and La Niña events. To investigate the microplastic load in a more urbanised environment, 3-monthly surveys were undertaken with surface waters, beach sediments, and M. gallloprovincialis mussels in Wellington Harbour, New Zealand, using samples from three sites for beach and mussel surveys, and two sites for the surface water tows. Weekly variation was also measured for beach sediments and mussel tissues. Again, no consistency was observed in temporal or spatial variation for any environmental or biological indicator, however the average pollutant loads were on par with reported results in other literature, particularly for M. galloprovincialis tissues. Temporally, the peak microplastic load in the tissues of the mussel, M. galloprovincialis, appeared to correlate with the peak load found within the surface waters of the harbour, indicating a possible relationship between plastic pollution in the environment and that which is found within organisms. Finally, the spatial variation observed within beach sediments was far larger than that seen throughout the mussel tissues, supporting the idea that beach sediments are microplastic sinks, but also susceptible to a range of environmental drivers including wind strength, wind direction, and sediment erosion. Throughout the Southern Ocean and within Wellington Harbour, particle characteristics were similar, in that microfibres were the prevailing synthetic morphotype – accounting for upwards of 90% of all particles found. These results are similar to reports from other current literature, but not associated with public knowledge that is currently in the media and represented in the legislation. The results of this thesis illustrate the importance of monitoring and managing the occurrence and effect of microplastics on both fine- and broad-scales of temporal and spatial variation and helps address the knowledge gap surrounding microplastics in the Southern Hemisphere.

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Sixty years of radiocarbon dioxide measurements at Wellington, New Zealand 1954–2014

10.5194/acp-2016-1110 ◽

2016 ◽

Cited By ~ 2

Author(s):

Jocelyn C. Turnbull ◽

Sara E. Mikaloff Fletcher ◽

India Ansell ◽

Gordon Brailsford ◽

Rowena Moss ◽

...

Keyword(s):

New Zealand ◽

Southern Ocean ◽

Co2 Emissions ◽

Southern Hemisphere ◽

Northern Hemisphere ◽

Seasonal Cycle ◽

Fossil Fuel ◽

Anthropogenic Sources ◽

Deep Waters ◽

Cape Grim

Abstract. We present 60 years of Δ14CO2 measurements from Wellington, New Zealand (41° S, 175° E). The record has been extended and fully revised. New measurements have been used to evaluate the existing record and to replace original measurements where warranted. This is the earliest atmospheric Δ14CO2 record and records the rise of the 14C "bomb spike", the subsequent decline in Δ14CO2 as bomb 14C moved throughout the carbon cycle and increasing fossil fuel CO2 emissions further decreased atmospheric Δ14CO2. The initially large seasonal cycle in the 1960s reduces in amplitude and eventually reverses in phase, resulting in a small seasonal cycle of about 2 ‰ in the 2000s. The seasonal cycle at Wellington is dominated by the seasonality of cross-tropopause transport, and differs slightly from that at Cape Grim, Australia, which is influenced by anthropogenic sources in winter. Δ14CO2 at Cape Grim and Wellington show very similar trends, with significant differences only during periods of known measurement uncertainty. In contrast, Northern Hemisphere clean air sites show a higher and earlier bomb 14C peak, consistent with a 1.4-year interhemispheric exchange time. From the 1970s until the early 2000s, the Northern and Southern Hemisphere Δ14CO2 were quite similar, apparently due to the balance of 14C-free fossil fuel CO2 emissions in the north and 14C-depleted ocean upwelling in the south. The Southern Hemisphere sites show a consistent and marked elevation above the Northern Hemisphere sites since the early 2000s, which is most likely due to reduced upwelling of 14C-depleted and carbon-rich deep waters in the Southern Ocean. This developing Δ14CO2 interhemispheric gradient is consistent with recent studies that indicate a reinvigorated Southern Ocean carbon sink since the mid-2000s, and suggests that upwelling of deep waters plays an important role in this change.

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