zaterdag 18 april 2015

EGU 2015 End Week Update: A Young Scientist participating in the Discussion

The General Assembly of the European Geophysical Union in 2015 has come to an end. I am filled with new information, new ideas, motivational energy, great experiences, and encounters with new and interesting people. Waiting for my flight back home, I have time to reflect on the final few days of this incredible experience.

Last blogpost, I gave an update of the first two days. I was working that day on my rebuttal for a new paper. I submitted the paper to a journal, which is using a short response time of two weeks, and with Easter and preparation for the conference, I had little time to work on it. On Wednesday, my personal program only needed me to be at the evening poster sessions, so during the day, I locked myself up in my hotel room and worked on the rebuttal (despite the beautiful weather). It is now with the editor for decision! Nevertheless, I had an interesting time in the evening.

Day 3: Wednesday 15 April 2015
Arriving late at the EGU conference site, I went directly towards the poster session (quickly getting a drink) to visit the first poster on my list. Poster sessions are great, because they enable you to better interact with the scientist and ask lots of questions. Also, for a Young Scientist, you can really engage in the discussion, in contrast to the presentation sessions, where you need to have a lot of guts asking a question in a room full of experts.

The first person I met was a very interesting and enthusiastic scientist from the University of Leicester. He and his group are slowly, but gradually mapping the complete crust around the British Isles and far surroundings (including parts of my study area Scandinavia). They use different geophysical observations to explore structures in the crust. What I like about the work is that they also look at the uncertainties in their observations and models, which allows a modeller (like me) to really test their work. Furthermore, I wanted to meet him, because I was asked to make a gravity model out of their data. So, it was good to finally meet the man behind the great work. Here, some preliminary results:
The seismic wave velocity and density estimates of a cross-section of the data set
You can clearly see that the density distribution follows physical principles. The deeper the material the higher the density is due to the pressure of overlying rocks. This is not always the case in other commonly-used density models, so I am eager to study the effects on the gravity signal. Thanks to the meet-up, I have more motivation to finish my modelling when I get back to my university. Continuing the poster session, I went to a scientific field which I no nothing about: Core-mantle boundary studies. I met a very smart and interesting guy that was willing to explain to me (newby in the field) how they measured deviations in that region. Incredible, using earthquakes to observe the deepest regions in the Earth. He was even willing to send me some papers that explained the principles and uncertainties. All in all, a great experience!

Just before I wanted to go to the city centre, I met up with my German colleagues from the University of Kiel and asked me to join a talk organised by the German Geophysical Society. During this talk, I learned about magnetic anomalies and how to observe and interpret them. The speaker gave a great historical overview of magnetic field measurements and showed me (and many others of course), that old data first needed to be corrected for daily variations. If this was not done, you could only interpret the velocity of the expedition vessel, around 10 knots. Nowadays, by using multiple magnetometers, they are able to remove this signal and study the magnetic signal in the underlying rocks. Then, he showed some applications, which blew my mind. Thanks to magnetic reversals and pole rotations, he was able to study crustal material that was already subducted into the mantle, and see what processes worked 100 million years ago. Wow!

Day 4: Thursday 16 April 2015
Today, I started the day with presentations about hydrological studies. In the first talk, a new hydrological model was presented, WGHM. It worked quite well, however it overestimated snow-melt in the spring season. I was wondering, could this be related to the observations done by the scientists on day 2, looking at satellite photos to map snow cover. He found a decline in snow cover during spring. I did not get the change to ask the question. After a while, I found that this session became to complicated for a non-expert like me, so I left and just wandered the exhibition area:

Exhibition area at the entrance of the conference building
A lot of nice companies and publishing agencies, however no gravity instruments. Still, the ESA and Google stands were quite interesting. After an hour, the Geodynamics session about the lithosphere and upper mantle started, which would keep me busy up till 19:00 in the evening.

Here, I list some of the interesting information I learned in the session. In the Atlas mountain range, the lithosphere plays a large role in the formation of this mountain belt. However, both strong and weak modelled viscosity structures give similar results. Furthermore, I learned that petrological processes are very important in the study of subsidence and uplift of the crust. Rocks like metabasite, and water insertion can lift or drop the crust by several hundreds of meters in geological time-scales. I should dive in that literature a bit more. Also, I learned about step-faults and some other tectonic behaviours.

Halfway through, the geodynamic medal lecture was given. An incredible talk about some problems of the lithosphere. Different types of earthquakes can be estimated by looking at the stress field. With a viscous sheet model, the complex stress field in Turkey can be modelled reasonably well. Observations of mantle dripping could explain localised earthquakes and tomographic velocity anomalies. His talk was followed by a presentation of the highest resolution tomographic model that clearly observed the North-American craton. A separation between the Greenland craton was noticeable.

The session was finished with some local studies of the crust and upper mantle, but one talk stood out quite well. The group from the University of Dublin had made a great inversion of different geophysical data sets to construct crustal models. They showed that crustal modelling only worked if all data sets were combined: seismic velocity observations, electromagnetic measurements, gravity observations, and petrological data. This was quite an intimidating talk that motivated me to do even a better job. During the poster session that evening, I presented my ideas on the my crustal modeling and its effect of using GIA observables. Introducing this extra data set could give us more understanding of the temperature structures in the upper mantle. I could talk the complete 1.5 hour and even the Core-Mantle guy dropped by for support. The day was ended by the Vening Meinesz Medal lecture, where the complete history of GPS observations was shown. Great work, which really deserved the Medal. Back in the hotel, I made some last alterations to my presentation and practised it a few times. Tomorrow, I would talk about Vening Meinesz and his submarine expeditions.

Day 5: Friday 17 April 2015
I was scheduled as second presenter in the session: History of Geophysics. After an inspiring talk about Wegener, it was my turn. With some nervousness in my body, I climbed the stage and relied on my experience and enthusiasm. I had a lot to show and came in a little bit of time-issues, but the convener let me go my way. Overall, I got good responses and hopefully people will visit our website (click here). My talk was followed by more historical interesting presentations about: science in the Ottoman Empire, history of seismic observation (two talks), and magnetic/meteorological observations during the Novara Expedition.

The complete dataset of Vening Meinesz of gravity observations during his 1934-1935 expeditions onboard the submarine K-XVIII
On Friday the GIA session was planned. So in the late morning, I visited the poster session where I had great discussions with my peers. I even met one of my Giants, who'd later had a great talk about the effect of GIA in oil exploration. Despite, the small amount of abstracts this year, the GIA sessions (poster and presentation) showed incredible research and it was great to see all the new ideas in the field. I even learned about a new dataset I should check out.

After the GIA session, I tried to follow some other talks about mantle plumes, but I found out that my brain was saturated. Grabbing a quick bite, I went to my hotel room and got an early night. This was my experience during the EGU 2015 General Assembly and I think I will need the rest of the week to reflect and organise all the new information. Hopefully, see you next year at EGU 2016.


2 opmerkingen:

  1. Doesn't the graph from the 1934-1935 on g-observations on board the submarine K-XVIII (partly) reflects the depth(s) of the seas 'sailed' through?

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    1. A very good question! The gravity signal does partly reflect the shape of the ocean floor, however the largest contribution is the shape of the Earth. Due to its rotation, it is elongated into an ellipsoid. This can be seen if you rearrange the measurements with respect to their latitude. Please check the website for some of the figures (expeditiewikipedia.nl) and go to "Gravity Explained". If you remove this first-order effect, you will have the free-air anomaly, which does correlate with the bathymetry.

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