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Weathering the storm from a research vessel

Weathering the storm from a research vessel

Fieldwork can take geoscientists to some of the most remote corners of the Earth in some of the harshest conditions imaginable, but stories from the field hardly make it into a published paper. In this blog post, Raffaele Bonadio, a PhD student in seismology at the Dublin Institute for Advanced Studies in Ireland, shares a particularly formidable experience in the field while aboard a research vessel in the North Atlantic Ocean.  

We knew it would be stormy that night. At the previous evening’s briefing, the captain of the ship, composed and collected, notified us that we needed to make a diversion from the planned route to avoid getting too close to the eye of the storm, “We’ll slow down the vessel…” “kind of five metres swell expected”. He was calm and comfortable. The crew members were calm and comfortable. We, the guest scientists, were not.

Why were we in the middle of the ocean?

I was part of a team of researchers from the Dublin Institute for Advanced Studies working on the project SEA-SEIS (Structure, Evolution and Seismicity of the Irish offshore). Our task was to deploy a suite of seismometers on the bottom of the North Atlantic Ocean from our research vessel, the RV Celtic Explorer, to investigate the geological evolution of the Irish offshore.

A map of the North Atlantic Ocean, showing the locations of seismometers deployed by the team’s research vessel, the RV Celtic Explorer. Credit: Raffaele Bonadio

Why study the Irish offshore?

The tectonic plate that Ireland sits on was deformed and stretched to form the deep basins offshore. The plate then broke, and its parts drifted away from each other, as the northern Atlantic Ocean opened. Hot currents in the convecting mantle of the Earth caused volcanic eruptions and rocks to melt 50-100 km below the Earth’s surface. These hot currents may have come from a spectacular hot plume rising all the way from the Earth’s core-mantle boundary (at 2891 km depth) to just beneath Iceland.

What do ocean bottom seismometers do?

Ocean bottom seismometers record the tiny vibrations of the Earth caused by seismic waves, generated by earthquakes and ocean waves. As the waves propagate through the Earth’s interior on their way to the seismic stations, they accumulate information on the structure of the Earth that they encounter. Seismologists know how to decode the wiggles on the seismograms to obtain this information. With this data, they can do a 3D scan (tomography) of what’s inside the Earth.

One of the research team’s seismometers being dropped into the North Atlantic Ocean. The instruments sink to the bottom of the ocean, where they measure the Earth’s movement. Credit: SEA-SEIS Team

In this project, we want to better understand how the structure of the tectonic plate varies from across the North Atlantic and what happens beneath the plates. And is there an enormous hot plume beneath Iceland, responsible for the country’s volcanoes today and the formation of Giant’s Causeway in Ireland? This is what we hope we will find out!

Experiencing an ocean storm

We were aboard the ship about 9 days and had just deployed “Ligea”, the 14th seismometer before the captain had notified us that a storm was heading our way.

While we were told in advance of the approaching storm, there was no way we could have imagined what it would be like to be in the middle of a stormy ocean. I had only heard some stories and I didn’t fully believe them…

I was awakened by the sound of my table lamp smashing on the ground, even the 15 cm protection edge around the table couldn’t help. The closet door opened and hit the wall. I managed not to fall off the bed, pointing my legs and make a crack with my back. I heard one of my colleagues laughing in the next cabin after a loud thud. “Did he just fall off the bed?” I thought to myself – his laugh did sound a bit of hysterical.

I realized a big wave had crashed on the side of the ship. I couldn’t believe that water and metal crashing together could make such a harsh bang. The previous evening was a continuation of bangs, splashes, sprinkles, bloops, clangs, and creaks … but even with all these noises and disturbances, I managed to sleep, exhausted from dizziness and sea-sickness.

I checked the clock on the wall: it was 3:20 in the morning. I looked at the porthole, due to the vertical movement my cabin was underwater half of the time. I walked through the cabin, trying to reach the toilet. “Oh, I wish they made the cabin smaller! I can’t reach both walls with my arms,” I said to myself. I opened the tap to refresh my face, the flowing water danced right and left across the basin. I then climbed up to the deck, I had to literally climb up the stairs. Up there I couldn’t see anything but darkness; I couldn’t see the boundary between the sky and the sea.

More than a week had passed since our departure, yet my body had still not adapted to this incessant movement. My eyes could not follow my body and my stomach did not react well, I couldn’t see anymore what was horizontal and what wasn’t. However, I wasn’t even scared, I believed nobody on the ship was (or is it only that I wanted to believe this?). It wasn’t fear, but rather an unceasing uncomfortable feeling: I knew I was more than 900 km from any dry land, in the middle of the North Atlantic Ocean, on a 66 m long vessel; I knew the captain and the crew were working hard to take us far from the storm. I was not scared…

In a few hours we were planning to deploy an ocean bottom seismometer, a very sophisticated device that is able to operate at huge pressures at the bottom of the ocean; released from the ship it would sink and install itself on the seafloor 4 km under the surface of the waves. In other words, a 200 kg ‘little orange elephant’, as the students who supported us from land every day liked to call it! “Will we be able to deploy? Will we be able not to crash the instrument on the sides? Will we instead be able to keep our balance and walk up to the deck?”

“Yes, we will.”

How did this look like? Find out more in this video:

 

So, what did we accomplish?

As part of the SEA-SEIS project, led by Dr. Sergei Lebedev, our research team successfully deployed 18 seismometers at the bottom of the North Atlantic Ocean. The network covers the entire Irish offshore, with a few sensors also in the UK and Iceland’s waters. The ocean-bottom seismometers were deployed between 17 September and 5 October, 2018, and will be retrieved in April of 2020.

To find out more about the SEA-SEIS Projects, have a look at SEA-SEIS or check out our introductory video.

By Raffaele Bonadio, Dublin Institute for Advanced Studies, Ireland

Geosciences Column: Scientists pinpoint where seawater could be leaking into Antarctic ice shelves

Geosciences Column: Scientists pinpoint where seawater could be leaking into Antarctic ice shelves

Over the last few decades, Antarctic ice shelves have been disintegrating at a rapid rate, likely due to warming atmospheric and ocean temperatures, according to scientists. New research reveals that one type of threat to ice shelf stability might be more widespread that previously thought.

A study recently published in EGU’s open access journal The Cryosphere identified several regions in Antarctica were liquid seawater could be leaking into vulnerable layers of an ice shelf.

Scientists have known for some time now that seawater can seep into an ice shelf’s firn layer, the region of compacted snow that is on its way to becoming ice. This seawater infiltration presents an issue to the ice shelf’s stability, since as the seawater spreads throughout the firn layer, the water can create fractures and help expand crevasses already present in the frozen material. Past research has shown that the presence of liquid brine from seawater within an ice shelf is correlated to increased fracturing and calving.

While ice shelf collapse doesn’t directly contribute to sea level rise, since the ice is already floating, stable ice shelves often push back on land-based ice sheets and glaciers, slowing down ice flow into the ocean. Past research has suggested that once an ice shelf collapses, the rate of ice flow from unsupported glaciers can greatly accelerate.

To better understand Antarctic ice shelves’ risk of collapse, the researchers involved with this new study sought to identify where ice shelf firn layers are vulnerable to seawater infiltration. Using Antarctic geometry data, they mapped out the potential ‘brine zones’ within the continent’s ice shelves. These are regions of the ice shelf where the firn layer is both below the sea level and permeable enough to let seawater percolate through.

The results of their analysis revealed that almost all ice shelves in Antarctica have spots where seawater can potentially leak through their layers, with about 10-40 percent of the continent’s total ice shelf area possibly at risk of infiltration.

Map of potential brine zones areas around Antarctica. Map shows areas where permeable firn lies below sea level (the brine zone), with the threshold for firn permeability defined as 750 kg m−3 (red), 800 kg m−3 (yellow) and 830 kg m−3 (blue) calculated using Bedmap2 surface elevation. Bar charts show the mean percentage area of selected ice shelves covered by the brine zone. (Credit: S. Cook et al. 2018)

The researchers compared their estimated points to a map of previously confirmed brine zones, observed through ice cores or radar surveys. After reviewing these records, they identified only one record of brine presence that hadn’t been highlighted by their developed model.

The study found many areas in Antarctica where seawater infiltration could be possible, but has not been previously observed. The findings suggest that this firn layer vulnerability to seawater might be more widespread than previously believed.

The researchers suggest that the most likely new regions where brine from seawater may be present includes the Abbot Ice Shelf, Nickerson Ice Shelf, Sulzberger Ice Shelf, Rennick Ice Shelf, and slower-moving areas of Shackleton Ice Shelf. The regions all contain large swathes of permeable firn below sea level while also subject to relatively warm air temperatures and low flow speeds, the ideal conditions for maintaining liquid brine.

The study points out that there are still many uncertainties in this research, considering the unknowns still present in the data used for mapping and the factors that may influence seawater infiltration. For example, some areas that have large predicted brine zones have an unusually think layer of firn from heavy snowfall. This is the case for the Edward VIII Bay in eastern Antarctica. “Our results indicate the total ice shelf area where permeable firn lies below sea level, but this does not necessarily imply that the firn contains brine,” the authors of the study noted in their article.

Given their findings, the researchers involved recommend that this potentially widespread influence on ice shelves should be further examined and assessed by future studies.

By Olivia Trani, EGU Communications Officer

References

Cook, S., Galton-Fenzi, B. K., Ligtenberg, S. R. M. and Coleman, R.: Brief communication: widespread potential for seawater infiltration on Antarctic ice shelves, The Cryosphere, 12(12), 3853–3859, doi:10.5194/tc-12-3853-2018, 2018.

Hoegh-Guldberg, O., D. Jacob, M. Taylor, M. Bindi, S. Brown, I. Camilloni, A. Diedhiou, R. Djalante, K.L. Ebi, F. Engelbrecht, J.Guiot, Y. Hijioka, S. Mehrotra, A. Payne, S.I. Seneviratne, A. Thomas, R. Warren, and G. Zhou, 2018: Impacts of 1.5ºC Global Warming on Natural and Human Systems. In: Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I.Gomis, E. Lonnoy, T.Maycock, M.Tignor, and T. Waterfield (eds.)]. In Press

Scambos, T. A.: Glacier acceleration and thinning after ice shelf collapse in the Larsen B embayment, Antarctica, Geophysical Research Letters, 31(18), doi:10.1029/2004gl020670, 2004.

Scambos, T., Fricker, H. A., Liu, C.-C., Bohlander, J., Fastook, J., Sargent, A., Massom, R. and Wu, A.-M.: Ice shelf disintegration by plate bending and hydro-fracture: Satellite observations and model results of the 2008 Wilkins ice shelf break-ups, Earth and Planetary Science Letters, 280(1–4), 51–60, doi:10.1016/j.epsl.2008.12.027, 2009.

State of the Cryosphere: Ice Shelves. National Snow & Ice Data Center

Imaggeo on Mondays: The calm before the storm

Imaggeo on Mondays: The calm before the storm

The picture was taken during the 2015 research cruise HE441 in the southern German Bight, North Sea. It features the research vessel Heincke, on a remarkably calm and warm spring day, forming a seemingly steady wake.

The roughly 55 metre long FS Heincke, owned by the German federal government and operated by the Alfred Wegener Institute, provides a great platform for local studies of the North Sea shelf. Eleven scientists and students from the University of Bremen, MARUM Research Faculty, University of Kiel, and Federal Waterways Engineering and Research Institute, along with the ship’s crew formed a great team under the supervision of chief scientist Christian Winter.

On deck, different autonomous underwater observatories were waiting to be deployed. Their purpose was to measure the seabed- and hydrodynamics in a targeted area of the German Bight. The investigation of the interaction between geomorphology, sedimentology and biogeochemistry is crucial to understand the processes acting on this unique and dynamic environment. In the German Bight various stakeholders with diverse interests come together. Profound knowledge, backed by cutting edge research, helps to resolve future conflicts between use and protection of the environment.

While this photo features a tranquil day at sea, some days later the weather and wave conditions got so bad that the cruise had to be abandoned. Storm Niklas, causing wave heights of more than three metres, made deployment and recovery of the observatories too dangerous for the crew, scientists, and delicate instruments.

Despite the severe weather, the research cruise was still able to gather important data with the time made available. Schedules on research vessels are tight and optimized to fit as much high-quality measurements as possible into time slots that are depending on convenient sea (tide) and weather conditions. State-of-the-art research equipment were prepared, deployed, recovered and assessed several times during the then only 8-day long cruise. Measurements were supported by ship based seabed mapping and water column profiling. Transit times, like the one depicted, were used to prepare the different sensors and instruments for the upcoming deployment.

The rare occasion of good weather combined with idle time was utilized to take this long exposure photo. A calm sea, a stable clamp temporarily attached to a handrail, and a neutral density filter were additionally required to increase the exposure time of the camera to 13 seconds, in order to capture this picture. The long exposure time smooths all movement relative to the ship, enhancing the effect of the wake behind the Heincke vessel.

Over the course of several years, regular Heincke research cruises and the collaboration between the different institutions has led to the successful completion of research projects, with findings being published in various journals, listed below.

By Markus Benninghoff, MARUM, University of Bremen, Germany

Further reading

Ahmerkamp, S, Winter, C, Janssen, F, Kuypers, MMM and Holtappels, M (2015) The impact of bedform migration on benthic oxygen fluxes. Journal of Geophysical Research: Biogeosciences, 120(11). 2229-2242. doi:10.1002/2015JG003106

Ahmerkamp, S, Winter, C, Krämer, K, de Beer, D, Janssen, F, Friedrich, J, Kuypers, MMM and Holtappels, M (2017) Regulation of benthic oxygen fluxes in permeable sediments of the coastal ocean. Limnology and Oceanography. doi:10.1002/lno.10544

Amirshahi, SM, Kwoll, E and Winter, C (2018) Near bed suspended sediment flux by single turbulent events. Continental Shelf Research, 152. 76-86. doi:10.1016/j.csr.2017.11.005

Krämer, K and Winter, C (2016) Predicted ripple dimensions in relation to the precision of in situ measurements in the southern North Sea. Ocean Science, 12(6). 1221-1235. doi:10.5194/os-12-1221-2016

Krämer, K, Holler, P, Herbst, G, Bratek, A, Ahmerkamp, S, Neumann, A, Bartholomä, A, van Beusekom, JEE, Holtappels, M and Winter, C (2017) Abrupt emergence of a large pockmark field in the German Bight, southeastern North Sea. Scientific Reports, 7(1). doi:10.1038/s41598-017-05536-1

Oehler, T, Martinez, R, Schückel, U, Winter, C, Kröncke, I and Schlüter, M (2015) Seasonal and spatial variations of benthic oxygen and nitrogen fluxes in the Helgoland Mud Area (southern North Sea). Continental Shelf Research, 106. 118-129. doi:10.1016/j.csr.2015.06.009

If you pre-register for the 2019 General Assembly (Vienna, 07–12 April), you can take part in our annual photo competition! From 15 January until 15 February, every participant pre-registered for the General Assembly can submit up three original photos and one moving image related to the Earth, planetary, and space sciences in competition for free registration to next year’s General Assembly!  These can include fantastic field photos, a stunning shot of your favourite thin section, what you’ve captured out on holiday or under the electron microscope – if it’s geoscientific, it fits the bill. Find out more about how to take part at http://imaggeo.egu.eu/photo-contest/information/.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.