ORCID Profile
0000-0002-6211-7007
Current Organisation
Auckland University of Technology
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Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-17288
Abstract: With the SARS-CoV-2 coronavirus came what media has deemed the & #8220 ort congestion pandemic& #8221 . Since it began, thousands of ships have been reported waiting outside heavily congested ports relying on anchoring gear to hold fast. While the shipping industry is known to contribute to air, water and noise pollution, the physical impact of shipping practices, such as anchor use on the seafloor, has received much less attention. With a regional survey using high-resolution (1 m) bathymetry data of a comparatively low congestion port in New Zealand-Aotearoa, we demonstrate that high-tonnage ship anchors excavate the seabed by up to 80 cm and the associated impacts are preserved for at least 4 years. This is the first characterisation of the intensity and extent of damage to the seafloor and benthic environment caused by high-tonnage ship anchoring. We demonstrate that the observed seabed damage is attributed to high-tonnage passenger and cargo vessels. Anchor use in port regions has significantly changed the structure of the seafloor, with downstream impacts on benthic habitats and ecosystem functions. Extrapolating these findings to a global scale, we estimate that between 6,000 and 20,000 km2 of coastal seafloor is adversely affected. With the predicted increase in global marine traffic, a less destructive method of managing high-tonnage vessels awaiting port calls is necessary to mitigate the impact of maritime activities on chemically and biologically important shallow marine environments.
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-17221
Abstract: Submarine eruptions dominate volcanism on Earth, but the recent eruption of Hunga Tonga& #8211 Hunga Ha& #699 apai volcano in January 2022 was one of the most explosive eruptions ever recorded. Many large calderas collapse during eruptions and the resulting morphology provides unvaluable information for understanding the processes during highly unpredictable eruptions.Here we present a detailed analyses of the post-eruption morphology of the caldera of the Hunga Tonga& #8211 Hunga Ha& #699 apai submarine volcano. We use the first multibeam bathymetry of the caldera, acquired only 5 months after the eruption on the MV Pacific Horizon, in May 2022.The multibeam data shows landslides with 0.5-1 km wide scars, mainly on the southern rim, with the deposits extending to the central part of the caldera. However, the flat inner caldera suggests that most of the material was deposited simultaneously to the caldera drop following the eruption, on the order of 800 m. Sediment cores collected inside the caldera show repeated turbidity current sedimentation pointing to ongoing mass wasting, which could have potentially led to eventual breaching of the rim on the north and east side. Submarine ridges were preserved on these sites, separating the inner caldera and two erosional channels on the outer part, which point to the main debris transport paths during the eruption. More than 50 active gas plumes are observed on the eastern side, located following a straight W-E transect, and on the northern side, where the vents are covering the collapse walls close to the eastern Hunga Tonga& #8211 Hunga Ha& #699 apai island. The presence of these vents and their distribution related to the morphology of the caldera, indicate the most energetic parts of the volcano, which can potentially still be hazardous. Our morphological analyses provide new insights of transport and depositional processes following highly energetic submarine eruptions.
Publisher: Elsevier BV
Date: 12-2020
Publisher: Frontiers Media SA
Date: 21-09-2020
Publisher: Springer International Publishing
Date: 24-09-2016
Publisher: Springer Science and Business Media LLC
Date: 07-05-2022
DOI: 10.1038/S41598-022-11627-5
Abstract: With the COVID-19 pandemic came what media has deemed the “port congestion pandemic”. Intensified by the pandemic, the commonplace anchoring of high-tonnage ships causes a substantial geomorphologial footprint on the seabed outside marine ports globally, but isn’t yet quantified. We present the first characterisation of the footprint and extent of anchoring in a low congestion port in New Zealand-Aotearoa, demonstrating that high-tonnage ship anchors excavate the seabed by up to 80 cm, with the impacts preserved for at least 4 years. The calcuated volume of sediment displaced by one high-tonnage ship ( 9000 Gross Tonnage) on anchor can reach 2800 m 3 . Scaled-up globally, this provides the first estimates of the footprint of anchoring to the coastal seabed, worldwide. Seafloor damage due to anchoring has far-reaching implications for already stressed marine ecosystems and carbon cycling. As seaborne trade is projected to quadruple by 2050, the poorly constrained impacts of anchoring must be considered to avoid irreversible damage to marine habitats.
Publisher: Elsevier BV
Date: 02-2013
Publisher: Elsevier BV
Date: 2015
Publisher: Springer International Publishing
Date: 24-09-2016
Publisher: Springer Science and Business Media LLC
Date: 16-01-2020
DOI: 10.1038/S41598-019-57049-8
Abstract: Submerged paloeshorelines preserved on the continental shelf indicate the depths of the most frequent (modal) low sea-levels within the glacial stages of the Late Quaternary. Here we have determined the south-east Australian shelf configuration when sea level was 40 m and 60 m below present-day sea-level (depths of the most persistent paleoshorelines within the last 120 ka), and we resolve the wave climate variations influencing the sediment transport pathways over this period. We present evidence demonstrating that the combination of shelf morphological evolution, changes in sea-level and variations in wave climate is responsible for latitudinal changes in sediment transport and deposition during the interglacial states. The paleoshoreline and shelf evolution is key to understanding the distribution of present-day shelf sand deposits and the contemporary sand budget response to future wave climate changes.
Publisher: Frontiers Media SA
Date: 14-12-2022
DOI: 10.3389/FEART.2022.1045716
Abstract: On inner continental shelves, a variety of coarse grained bedforms, such as gravel dunes, are shaped by hydrodynamic and morphodynamic processes. The formation and evolution of bedforms reflect a balance between seabed and coastal morphology, sediment type and availability, and regional hydrodynamics. Yet, observing bedform evolution directly in the marine environment is rare, mostly due to the lack of repeat seafloor mapping surveys. In this study we use repeat bathymetry from 3 surveys over 4 years from the western Cook Strait/Te Moana-o-Raukawakawa region, New Zealand/Aotearoa. We integrate seabed morphology characterisation with sediment classification and regional hydrodynamic modelling, to investigate the evolution of gravel dunes under multi-directional current conditions. The repeat seafloor mapping reveals morphological changes to plan-view dune geometry and bifurcation of crestlines, with maximum observed vertical changes up to 3 m at water depths between 60 and 80 m. However, no dune migration was detected. Our hydrodynamic model shows that the most prominent morphological changes over the gravel dunes are spatially correlated with eddy formation, and high multi-directional near-bottom currents, reaching maximum speeds of ∼4 m s −1 and bottom stress of & N m −2 in each tidal cycle. We demonstrate that the average hydrodynamic conditions in this region are capable of mobilising coarse-grained sediment (i.e., sand to gravel), indicating that the observed morphological changes over multi-year time scales are a result of continuous remobilisation by currents, rather than extreme or storm events. Our findings demonstrate the highly dynamic nature of the seabed in Cook Strait, and the need for regular, repeat mapping surveys to ensure up-to-date seabed morphology information.
Publisher: Elsevier BV
Date: 08-2016
Publisher: Geological Society of London
Date: 12-07-2017
DOI: 10.1144/SP461.16
Publisher: Elsevier BV
Date: 03-2015
Publisher: Elsevier BV
Date: 06-2011
Publisher: Elsevier BV
Date: 04-2023
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-4521
Abstract: On inner continental shelves, a variety of coarse grained bedforms, such as gravel dunes, are shaped by hydrodynamic and morphodynamic processes. Repeat, high-resolution, multibeam surveys are crucial to identify geomorphological changes on the seafloor, especially in the extremely dynamic shallow waters ( 200 m water depth). Timeseries bathymetric datasets allow us to measure and monitor spatial- and temporal changes in submarine bedforms and determine their evolution patterns. This is important for a better understanding of the sediment transport processes and the related hydrodynamics, but also to determine the settings for benthic ecosystems and identify changes in seafloor geomorphology to prevent potential damage of offshore infrastructure and maritime pathways.We present three multibeam data sets acquired in 2017, 2020 and 2021 over a field of gravel-sand bedforms located in the high-energy Cook Strait / Te Moana-o-Raukawa. In this study we combine timeseries bathymetric data, ground-truth data (video footage and sediment s les) and oceanographic modelling to understand the sediment dynamics in the area. Results show that coarse sand and gravel field of dunes with superimposed megaripples have undergone intricate morphological changes. The ~100-m length and ~15-m height submarine dune crests bifurcate, becoming more complex between 2017-2020, followed by the reforming of dune crests between 2020-2021. Hydrodynamic modelling suggests there is an interaction between the tidal near-bottom currents and the sediment transport, creating a morphological positive feedback, which might be leading the complex bedform morphological changes observed in the repeated mapping surveys.This study reveals the dynamic nature of the seabed over short time-scales (years) in highly dynamic areas, such as the tidally vigorous Cook Strait region. Our findings demonstrate the importance of repeat multibeam mapping in understanding of the rate and scale of changes on the seafloor.
Publisher: Elsevier BV
Date: 10-2010
Publisher: Elsevier BV
Date: 2021
Publisher: Elsevier BV
Date: 05-2018
Publisher: Elsevier BV
Date: 2016
Publisher: American Geophysical Union (AGU)
Date: 04-2013
DOI: 10.1002/JGRC.20168
Publisher: Elsevier BV
Date: 09-2014
Publisher: Elsevier BV
Date: 06-2014
Publisher: Elsevier
Date: 2012
Publisher: Elsevier BV
Date: 09-2023
Publisher: MDPI AG
Date: 07-05-2018
Publisher: Elsevier BV
Date: 08-2016
Publisher: Wiley
Date: 17-09-2020
DOI: 10.1002/ESP.4986
Location: Spain
Start Date: 2020
End Date: 2020
Funder: Ministry of Business, Innovation and Employment
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