It is 2019 and it is spring time in Vienna again. The night train from Hamburg to Vienna was as always a great experience and so the conference was set up for a good start. The sun is giving everybody a big smile (at least for the start) and so and eventful week lies ahead of us.
The first day was fully covered for me by sea level science. The sea level session covered as always a wide range of topics. From reconstructions over land movements, from GIA to the political site of the problem. Unfortunately, my favorite topic, the palaeo-reconstructions were only covered by a very small number of talks (probably just one).
I have also to get used to the new schedule of seven talks per session, but I will certainly write about it more later this week. I also went to a poster session, which are now in parallel to the talk-sessions. So a lot of changes, which all need some adaptions.
During the week I will have a talk and a poster, but both will happen towards the end. I am looking forward for many interesting topics, talks and posters and of course the most important part of a conference: meeting other scientists.
Just after I have attended a conference on seasonal and decadal prediction at NCAR in Boulder/Colorado, my next stop was at the PALSEA and QUIGS meeting in Galloway/New Jersey. It was the third time that I attended a PALSEA and as the other two times it was a great opportunity for me. The main topic of the conference was the sea-level and climate change during the last and other interglacials.
Many talks surrounded the available data and their interpretation. In this context it is a very complex task to bring together on the one side the many different proxies and evidences of sea-level height during that period and on the other side to explain their causes by the changes of ice-sheets in the higher latitudes and the reaction on them by the Earth. As a consequence there were many interesting discussions surrounding this field and many different viewpoints were heard. Specific questions around when the last interglacial exactly started, how high the sea-level was during that period and how the exact evolution of sea-level happened during that time were often discussed during this week. Most discussions were evidence driven, trying to make sense of the sometimes contradicting results and their uncertainties.
Also the understanding of the consequences of these results played an important role, as sea-level change is not happening isolated. It requires the build up or melting of ice shoot and with it a change in climate. In a climate system, as we know from looking around us today, that is highly connected all the climate sub-components, especially atmosphere, cryosphere and ocean have to tell the same story.
Myself have presented a poster on the last interglacial sea-level evolution and had several interesting discussions on this topic. Also the field trip, which showed us the study fields of salt marches, which are used to investigate Holocene sea-level change at the East American coast was very informative. Seeing the data collection first hand always helps to understand the topic better and getting better results at the computer in your own office. All in all it was a great opportunity for me, which was made possible by the financial contribution by the organisers, which allowed me to attend.
It was the fourth day and at this time a conference gets a bit exhausting. I started the day with a visit to statistical post-processing and walked then on to the sea level session for the rest of the morning. As I have worked in my past position in sea-level science the topic is still very familiar for me. Especially the large range of topics, from palaeo-reconstructions to engineering advice makes a visit to such a session always an interesting adventure. After lunch I switched to the precipitation databases session, which was after the break followed with homogenisation approaches. The end of the day was as always filled with the poster session.
Tomorrow, I will finally have the opportunity to show my own work. In the afternoon I will have my talk on seasonal prediction and in the evening a poster on past sea-level change. Traditionally, the friday tends to be quite empty and it is usually not so good to have the contributions so late in a conference, but I am sure it will still be an interesting final day.
The new year has started and in the recent weeks two new papers with myself in the author list have been published. Both are covering a wide spectrum and my contribution was in both cases more something I would classify as statistical assistance. Therfore, I will keep my comments brief at this place and just quickly introduce the topics.
Speleothem evidence for MIS 5c and 5a sea level above modern level at Bermuda
This paper is about the sea-level height at Bermuda at roughy 70,000 years back. It is mainly a geological paper and focusses on the evidence from speleotherms, that indicate that sea-level was positive compared to today at that time. That is important, because the rest of the world has in many places lower than modern sea-level at that time. A plot in the later part of the paper shows, that the difference at different locations in the carribean can be up to 30-40m. Explained can this be with GIA modelling and the paper is therefore a good help to better calibrate those models.
Wainer, K. A. I.; Rowe, M. P.; Thomas, A. L.; Mason, A. J.; Williams, B.; Tamisiea, M. E.; Williams, F. H.; Düsterhus, A.; Henderson, G. M. (2017): Speleothem evidence for MIS 5c and 5a sea level above modern level at Bermuda, Earth and Planetary Science Letters, 457, 325-334
Hindcast skill for the Atlantic meridional overturning circulation at 26.5°N within two MPI-ESM decadal climate prediction systems
The second paper focusses on the hindcast skill of two decadal forecasting systems of the Atlantic meridional overturning circulation (AMOC). It shows that both system have significant hindcast skill in predicting the AMOC for up to five years in advance, while an uninitialised model run has not. The time series for evaluationg the systems are still quite short, but the extensive statistics in the paper allows to transparently follow the argument, why the system do have this capability.
In my final post on the background on the recently published paper, I would like to take a look into the future of this kind of research. Basically it highlights again what I have already written at different occasions, but putting it together in one post might make it more clear.
Palaeo-data on sea-level and its associated datasets are special in many regards. That is what I had written in my background post to the last paper and therefore several problems occur when these datasets are analysed. Therefore, as I have structured the problems into three fields within the paper I also like to do it here.
The datasets and their basic interpretation are the most dramatic point, where I expect the greatest steps forward in the next years. Some paper came out recently that highlight some problems, like the interpretation of coral datasets. We have to make steps forward to understand the combination of mixed datasets and this can only happen when future databases advance. This will be an interdisciplinary effort and so challenging for all involved.
The next field involved are the models. The analysis is currently done with simple models, which has its advantages and disadvantages. New developments are not expected immediately and so more the organisation of the development and sharing the results of the models will be a major issue in the imminent future. Also new ideas about the ice sheets and their simple modelling will be needed for similar approaches as we had used in this paper. Statistical modelling is fine up to a point, but there are shortcomings when it goes to the details.
The final field is the statistics. Handling sparse data with multidimensional, probably non-gaussian uncertainties has been shown as complicate. There needs to be new developments of statistical methodology, which are simple on the one side, so that every involved discipline can understand them, but also powerful enough to solve the problem. We tried in our paper the best to develop and use a new methodology to achieve that, but there are certainly different approaches possible. So creativity is needed to generate methodologies, which do not only deliver a value for the different interesting parameters, but also good and honest uncertainty estimates.
Only when these three fields develop further we can really expect to get forward with our insights into the sea-level of the last interglacial. It is not a development, which will happen quickly, but I am sure that the possible results are worth the efforts.