Marine geophysical research at the University of Auckland focusses in studying the seafloor and the first few hundred meters beneat it.  Current research includes:

Natural gas hydrates: Gas hydrate, an ice-like form of water with natural gas, is found in sediments on many continental margins.  Ingo Pecher has been active in gas hydrate research since the 1990s.

Current research topics includes gas hydrates as a potential source of energy as part of an MBIE-funded programme (Gas Hydrates: Economic opportunities and environmental implications), the link between gas hydrates and fluid flow, the interaction between gas hydrates and seafloor stability (including IODP Expedition 372), as well as dynamics of gas hydrate systems, i.e., how gas hydrates respond to changes of environmental conditions over time.

Gas hydrates have been studied in New Zealand since the 1980s.  GNS Sciences started significant research in gas hydrates in the 2000s with a focus on sustainable production of energy followed by three externally funded programmes from 2010 in which the University of Auckland plays a major role focussing on gas hydrate exploration, seafloor stability, and modelling (e.g., Bai et al., 2016, Oluwunmi et al., submitted).  A recent workshop sponsored by the American Association of Petroleum Geologists was held in Auckland in 2019 with a focus on utilising gas hydrates for transitioning to a low-carbon economy.

We are furthermore investigating the role of gas hydrates in seafloor processes.  Results of a decade-long collaborative research led to an Integrated Ocean Discovery Program (IODP) proposal and Expedition 372 to study the relation between gas hydrates and landslides (http://publications.iodp.org/preliminary_report/372/).  Recent heat flow (Pecher et al., 2017) and modelling (Oluwunmi et al., submitted) is changing our perception of the time scales of gas hydrate adjustment: Dissociation resulting from environmental changes may take thousands of years with significant implications for seafloor stability, near-seafloor fluid flow, and carbon cycling.

Seafloor pockmarks:  Large parts of the Chatham Rise are covered by seafloor pockmarks, circular depressions on the seafloor.  The pockmarks are bathymetrically constrained – they occur only in water depths great than ~500 m.  This led to the suggestion that gas hydrates are involved in their formation.  We are part of an IODP pre-proposal for ocean drilling to study these pockmarks (924-Pre), in which we lead hydrate and shallow-seismic aspects.

We have recently been have been awarded a Marsden Fund grant to conduct geophysical surveys to study the origin of these pockmarks.  This research is motivated by one of the key questions in paleo-climate research:  Why did atmospheric CO2 concentration remain in a range of 190-280 ppm throughout the ice ages in the last 800,000 years?  This is in particular important now that concentrations at >400 ppm are  outside this range.  For this, a buffer is required for repeated uptake and release of CO2. It is commonly thought the deep ocean constituted such a buffer. However, evidence is now mounting that CO2 is instead repeatedly released from the seafloor. Based on anomalies in sediment cores, the Chatham Rise and Bounty Trough east of the South Island appear to be key locations for such CO2 release (Stott et al., 2019).  A huge part of this region is covered by seafloor pockmarks, crater-like features usually caused by sudden escape of fluids and gas. These pockmarks appear to have been formed repeatedly during ice ages. We therefore suggest they were caused by release of CO2, which we plan to test by illuminating the sub-seafloor with scientific seismic data and by conducting modelling. This project investigates a key component of the new hypothesis that release of CO2 from the seafloor during ice ages may have buffered atmospheric CO2 concentrations: the “valve” mechanism that controls CO2 release.

We are searching for a PhD and an MSc student (see Student Opportunities).

Fluid expulsion on the Hikurangi Margin: As part of a GNS Science-led, MBIE-supported initiative, we are investigating fluid expulsion on the Hikurangi Margin focussing on quantitative analysis of seismic reflection data.  This includes full-waveform inversion as well as interpretation of reflection seismic and ocean-bottom seismometer data.

Acoustic Characterization of Gas in Ocean Water: This is a new NIWA-led, MBIE-supported programme aiming at characterizing gas bubbles released from the seafloor using broadband acoustic survey.

Gas-bubble streams in the water column have been observed on echosounder and multibeam data for many years. Characterization of the bubble streams both in terms of fluxes and chemical composition however, can so far only be achieved with direct sampling. The development of broadband, multi-frequency water column imaging now holds significant promise for constraining the chemistry of bubble-forming gases and for improving flux estimates with far-reaching consequences for studying carbon fluxes from the seafloor into the ocean and atmosphere.

A grant recently awarded to the NIWA by MBIE aims at developing the methodology for acoustic characterization of gas in water based on a recent pilot survey in a collaboration between scientists at NIWA, the University of Auckland, Callaghan Innovation, the University of Tasmania, and the University of New Hampshire.  We are leading the seafloor-geophysical aspects of this project and are searching for a PhD student (see Student Opportunities)

 

References

Bai, H., Pecher , I. A., Adam, L., and Field, B. D., 2016, Possible link between weak bottom simulating reflections and gas hydrate systems in fractures and macropores of fine-grained sediments: Results from the Hikurangi Margin, New Zealand: Mar. and Petrol. Geol., v. 71, p. 225-237.

Mountjoy, J. J., Pecher , I., Henrys, S., Crutchley, G., Barnes, P. M., and Plaza-Faverola, A., 2014, Shallow methane hydrate system controls ongoing, downslope sediment transport in a low-velocity active submarine landslide complex, Hikurangi Margin, New Zealand: Geochem. Geophys. Geosyst., v. 15, no. 11, p. 4137–4156.

Oluwunmi, P., Pecher , I. A., Archer, R., Reagan, M. T., and Moridis, G. J., submitted, 2019, The response of gas hydrates to tectonic uplift: Geophys. Res. Lett.

Pecher, I. A., Villinger, H., Kaul, N., Crutchley, G. J., Mountjoy, J. J., Huhn, K., Kukowski, N., Henrys, S. A., Rose, P. S., and Coffin, R. B., 2017, A fluid pulse on the Hikurangi Subduction Margin: Evidence from a heat hlux transect across the upper limit of gas hydrate stability: Geophys. Res. Lett., v. 44, no. 24, p. 12385-12395.

Stott, L., Davy, B., Shao, J., Coffin, R., Pecher , I., Neil, H. L. R., P., and Blanke, S., submitted, CO₂ Release from Pockmarks on the Chatham Rise-Bounty Trough at the Glacial Termination: Paleoceanography.

Last updated: 7 Feb. 2020