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.

woensdag 15 april 2015

EGU 2015 Mid Week Update: A Young Scientist among Giants

With the European Geophysical Union General Assembly halfway there, it is time for me to sit and write down all my experiences as a young scientist. From sitting behind your desk, interacting with max 3 living beings (one of them is my office plant), to literally meeting thousands of scientists from around the world can be a little bit exhausting. Therefore, I have my mid week moment-of-zen, which I use to write this blog.

Pre-EGU2015 adventures:
Due to a tight-scheduled revision of one of my papers, I had little time to design and print my poster, forcing me to drop by the print office on my way to the airplane. After a provocatively slow printer, I hurried to the airplane and got my flight to Vienna.

After extra long minutes my poster was ready to go!
Arriving at Vienna, I checked in my hotel, after a short train ride from the airport. During the waiting on the platform and the train ride, you could spot them already: other scientists, still a little weary from the flight and carrying to much luggage, but above all the characteristic poster holder. I forgot mine, so they all looked back at me with empathy, the first crease awls on my poster were visible. 

After a good night sleep I set the alarm early, I needed to get my entrance badge. At 08:00 o'clock registration would open, but at 07:30 lines of scientists started to form. Luckily, I was there at 07:29, so in front and got my badge after waiting half an hour.

Let the learning begin!
Day 1: Monday 13 April 2015
With my notebook as equipment I charged inside, took a quick look and went to my first session. The first presentation was about a new theory in plate generation. It neatly explained why Earth has plate tectonics and Venus does not! This speaker linked his theory to the tiniest elements in Geosciences, crystal structures. Wow, this would become a very nice week.

During the day, I learned about how crystal structures could have an effect on long-term behaviour of crust and mantle and advancements in seismic imaging. Not bad for a gravity scientist. The most interesting talk was about melt distributions in a convecting mantle. The speaker spoke about his theory that explained why geophysical data sometimes show a sharp LAB boundary and sometimes they do not. This intrigued me, because I run across this problem in my own studies. Using a theory called redox melting of CO2 in the mantle, the asthenosphere can have extra melting (Oxygen somehow lowers melting point) regimes above areas with a lot of diamonds (C). This results in a sharp signal in geophysical observations, like seismic tomography. This concept only works when there is convection in the mantle. Could it be that where no clear LAB signal is present, we have stagnant convection areas? Back home, I need to read up on this. 

During transfer between talks and posters, I met a lot of old friends and colleagues and in the evening, I ended up with some of them in a cool restaurant designed like a library. I slept like a baby.

Day 2: Tuesday 14 April 2015
After a warm, but good night sleep (broken airco), I was ready to fill my brains with knowledge. I decided to see what the cryosphere people were doing. One of the speakers talked about his life work, mapping snow coverage on the Northern Hemisphere, using satellite photography and many other techniques. One of the interesting (and maybe a little bit troubling) things was that he saw a decline in snow cover in the spring months during the 50 years of satellite data coverage. Could this be a climate change signal or do the seasons change a little bit with respect to our calendar?

During the same session, one of my (young) Giants was presenting his results on ice melting of the Northern ice sheets (Canada, Greenland, Iceland, Svalbard, Novaya Zemlya and other Russian islands). He combined GRACE gravity measurements and ICESat/Cryosat altimetry measurements to observe this ice mass changes with extreme spatial accuracy. You could see ice mass changes of individual ice sheets. Very cool! All three satellite observations fitted perfectly on top of each other. Hooray for the satellites and remote sensing.

After an interesting session about seismic anisotropy, I had a quick lunch with some colleagues of mine. Quick, because I did not want to miss the medal lecture of one of my other Giants. I have been reading papers of this medalist from the start of my PhD. They quickly helped me to get accustomed in geophysical modelling (my background was satellite orbit determination). I briefly met him on a field trip in the Italian Apennines and discussed topics like elastic strength of the lithosphere and mantle rheology. His talk was incredible and an inspiration to continue my work with more motivation and energy.

After the medal lecture, I went together with a friend, which I met on my first conference as starting-PhD and now coincidently sat next to me, to listen to a speaker that boldly stated that the Indian collision with Asia could not have been initiated before 20 Ma. All the geologist in the room silently (or less silently) struggled with this concept, but his geophysical modelling was very good and they could not break his theory.

I finished the day with presentations and posters about how to use gravity in geosciences, more common ground for me. Interesting results, especially the fact that satellite-based gravity gradients are not sensitive to deep mantle effects, which could help in constraining crustal masses much better. Again a good day!

I now have to run to the poster session of today, because I want to know more about the core-mantle boundary and its effects on the Earth system...or I could sit in the sun in front of the entrance...

Scientists in the Sun

woensdag 1 april 2015

Gravity Expeditions at Sea

This week one of the major milestones of the Vening Meinesz project is a fact. The website is online, where you can follow the adventure of professor Vening Meinesz onboard the submarine K-XVIII! He sailed from Den Helder, Netherlands to Surabaya, Indonesia via a large detour, visiting ports on several continents. Along the way he measured the gravity field of the Earth with extreme precision. He did this with a pendulum apparatus onboard a moving vessel. A great achievement done by a great scientist. Please explore the website and tell me what you think of it.

Enter here!

Oh, for none Dutch speakers, just skip the introduction of the main app, the expedition of Vening Meinesz is written in English. Yet, if you can read Dutch, please check my interview in the TU Delta (University paper) about the project, here (page 18).

The captain and crew of the K-XVIII with the professor among them.