ORCID Profile
0000-0002-4689-018X
Current Organisation
National Institute of Water and Atmospheric Research Wellington
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Publisher: American Geophysical Union (AGU)
Date: 06-2020
DOI: 10.1029/2019JC015882
Abstract: Basal melting of ice shelves is inherently difficult to quantify through direct observations, yet it is a critical factor controlling Antarctic mass balance and global sea‐level rise. While much research attention is paid to larger ice shelves and those experiencing the most rapid change, many smaller, unstudied ice shelves offer valuable insights. Here, we investigate the oceanographic conditions and melting beneath the Sørsdal ice shelf, East Antarctica. We present results from the 2018/2019 Sørsdal deployment of the University of Tasmania's autonomous underwater vehicle nupiri muka . Oceanography adjacent to and beneath the ice shelf front shows a cold and relatively saline environment dominated by Winter Water and Dense Shelf Water, while bathymetry measurements show a deep (∼1,200 m) trough running into the ice shelf cavity. Two multiyear deployments of Autonomous Phase‐sensitive Radar Echo Sounders on the surface of the ice shelf show weak melt rates (average of 1.6 and 2.3 m yr −1 ) with low temporal variability. These observations are supported by numerical ocean model and satellite estimates of melting. We speculate that the presence of a ∼825 m thick (350 m to at least 1,175 m) homogeneous layer of cold, dense water blocks access from warmer waters that intrude into Prydz Bay from offshore, resulting in weak melt rates. However, the newly identified trough means that the ice shelf is vulnerable to any decrease in polynya activity that allows warm water to enter the cavity. This could lead to increased basal melting and mass loss through this sector of Antarctica.
Publisher: Springer Science and Business Media LLC
Date: 12-01-2021
Publisher: American Geophysical Union (AGU)
Date: 03-2020
DOI: 10.1029/2019EA000695
Abstract: Bubble emission mechanisms from submerged large igneous provinces remains enigmatic. The Kerguelen Plateau, a large igneous province in the southern Indian Ocean, has a long sustained history of active volcanism and glacial/interglacial cycles of sedimentation, both of which may cause seafloor bubble production. We present the results of hydroacoustic flare observations around the underexplored volcanically active Heard Island and McDonald Islands on the Central Kerguelen Plateau. Flares were observed with a split‐beam echosounder and characterized using multifrequency decibel differencing. Deep‐tow camera footage, water properties, water column δ 3 He, subbottom profile, and sediment δ 13 C and δ 34 S data were analyzed to consider flare mechanisms. Excess δ 3 He near McDonald Islands seeps, indicating mantle‐derived input, suggests proximal hydrothermal activity McDonald Islands flares may thus indicate CO 2 , methane, and other minor gas bubbles associated with shallow diffuse hydrothermal venting. The Heard Island seep environment, with subbottom acoustic blanking in thick sediment, muted 3 He signal, and δ 13 C and δ 34 S fractionation factors, suggest that Heard Island seeps may either be methane gas (possibly both shallow biogenic methane and deeper‐sourced thermogenic methane related to geothermal heat from onshore volcanism) or a combination of methane and CO 2 , such as seen in sediment‐hosted geothermal systems. These data provide the first evidence of submarine gas escape on the Central Kerguelen Plateau and expand our understanding of seafloor processes and carbon cycling in the data‐poor southern Indian Ocean. Extensive sedimentation of the Kerguelen Plateau and additional zones of submarine volcanic activity mean additional seeps or vents may lie outside the small survey area proximal to the islands.
Publisher: Springer Science and Business Media LLC
Date: 21-01-2022
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-2517
Abstract: Climate warming is increasing glacial melt on the Antarctic continent, in turn shifting hydrostatic pressure on subglacial and surface lakes. This has a direct impact on the rates ofgroundwater discharge, with feedbacks to local and regional ocean and climate dynamics, as well as ice sheet retreat rates. The magnitude and ersity of Antarctic subglacial flux and its interaction with the marine realm is currently unknown, yet it may be critical to projecting hydrologic dynamics and the fate of coastal ecosystems in the Ross Sea under future climate change scenarios. Here, we report the first holistic quantification of the magnitude, composition, and impact of subglacial fluxes documented in the Antarctic region. With extensive water column, sediment, and ecological s ling we have explored the magnitude, biogeochemical composition, and temporal variability of subglacial water and dissolved constituent fluxes in the Ross Sea. We will highlight initial findings from this research, including the magnitude and spatial variability of subglacial fluxes from the Victoria Land coast, and the sphere of influence of these fluids on the coastal marine ecosystem in the Ross Sea.& We will place discoveries to date in the context of this emerging field, including incorporation into ice sheet and oceanographic models of the region. With this, we provide the first direct evidence of land-sea connectivity in the Ross Sea coastal environment through submarine groundwater discharge (SGD) and establish a critical baseline for measuring and predicting future change.&
Publisher: Frontiers Media SA
Date: 24-01-2022
DOI: 10.3389/FEART.2021.785396
Abstract: Understanding fluid expulsion is key to estimating gas exchange volumes between the seafloor, ocean, and atmosphere for locating key ecosystems and geohazard modelling. Locating active seafloor fluid expulsion typically requires acoustic backscatter data. Areas of very-high seafloor backscatter, or “hardgrounds,” are often used as first-pass indicators of potential fluid expulsion. However, varying and inconsistent spatial relationships between active fluid expulsion and hardgrounds means a direct link remains unclear. Here, we investigate the links between water-column acoustic flares to seafloor backscatter and bathymetric metrics generated from two calibrated multibeam echosounders. Our site, the Calypso hydrothermal vent field (HVF) in the Bay of Plenty, Aotearoa/New Zealand, has an extensive catalogue of vents and seeps in & m water depth. We demonstrate a method to quantitatively link active fluid expulsion (flares) with seafloor characteristics. This allows us to develop predictive spatial models of active fluid expulsion. We explore whether data from a low (30 kHz), high (200 kHz), or combined frequency model increases predictive accuracy of expulsion locations. This research investigates the role of hardgrounds or surrounding sediment cover on the accuracy of predictive models. Our models link active fluid expulsion to specific seafloor characteristics. A combined model using both the 30 and 200 kHz mosaics produced the best results (predictive accuracy: 0.75 Kappa: 0.65). This model performed better than the same model using in idual frequency mosaics as input. Model results reveal active fluid expulsion is not typically associated with the extensive, embedded hardgrounds of the Calypso HVF, with minimal fluid expulsion. Unconsolidated sediment around the perimeter of and between hardgrounds were more active fluid expulsion sites. Fluids exploit permeable pathways up to the seafloor, modifying and refashioning the seafloor. Once a conduit self-seals, fluid will migrate to a more permeable pathway, thus reducing a one-to-one link between activity and hardgrounds. Being able to remotely predict active and inactive regions of fluid expulsion will prove a useful tool in rapidly identifying seeps in legacy datasets, as well as textural metrics that will aid in locating nascent, senescent, or extinct seeps when a survey is underway.
Location: United Kingdom of Great Britain and Northern Ireland
Location: New Zealand
No related grants have been discovered for Erica Spain.