Category: Uncategorized

Ida Ringgaard successfully defended her PhD

The 29th of June ice2ice PhD Ida Magrethe Ringgaard succesfully defendend her PhD on “Sensitivity of Arctic sea ice change on climate in the coupled climate model EC-Earth”.

From left, supervisor Eigil Kaas, Assesment committee chairman Anders Svensson, supervisor Jens Hesselbjerg, PhD Ida Magrethe Ringaard, Assesment committee members Professor Gunilla Svensson, Meteorologiska Institutionen, Stockholm University  and Professor Timo Vihma, Finnish Meteorological Institute, and finally collaborator and researcher Shuting Yang.

In the PhD she investigated the sensitivity of the climate to changes in the Arctic sea ice using an atmosphere-ocean coupled climate model. Ida has found that Barents-Kara sea ice loss might be linked to a weak cooling over parts of Europe in winter only present for the temporal mean winter temperatures. However the coldest winters did not show a statistically significant cooling over Europe for any amount of sea ice loss in the Barents-Kara Seas.

She also used the warm RCP8.5 scenario to look at sea ice loss in the period 1850-3200 and found that the Arctic transitioned from having a perennial sea ice cover to an ice-free Arctic Ocean. The loss of the Arctic sea ice appeared to lead to a shift in trends for some key parameters such as the precipitation variability which increased and the Atlantic Meriodional Ocean Circulation which stabilized after an initial reduction as well as a change in the Arctic Ocean stratification which strengthened.

Ida was supervised by:

  • Professor Eigil Kaas, Physics of Ice, Climate and Earth, Niels Bohr Institute, University of Copenhagen
  • Professor Jens Hesselbjerg Christensen, Physics of Ice, Climate and Earth, Niels Bohr Institute, University of Copenhagen

and in the assesment committee was:

  • Associate Professor Anders Svensson, Physics of Ice, Climate and Earth, Niels Bohr Institute, University of Copenhagen
  • Professor Gunilla Svensson, Meteorologiska Institutionen, Stockholm University 
  • Professor Timo Vihma, Finnish Meteorological Institute   

Evangeline Sessford successfully defended her thesis!

Last Friday Evangeline Sessford successfully defended his thesis for the PhD degree at the University of Bergen. The thesis is entitled: “Hydrography in the Nordic Seas During Dansgaard-Oeschger Events 8-5”. The assessment committee consisting of Professor, ph.d. Mary Elliot, Paleoclimats Paleoenvironnements Bioindicateurs, LPG Université de Nantes, France, Researcher, ph.d. Jeroen Groeneveld MARUM – Zentrum für Marine Umweltwissenschaften Universität Bremen, Germany and Haflidi Haflidason, Department of Earth Science, University of Bergen.

You can read more about the thesis here, unfortunately only in Norwegian.

3 happy ice2ice Msc students

Today 3 ice2ice Msc students successfully defended their MSc thesis at the Niels Bohr Institute.

The three students have all been working with chemical ice core proxies, but on very different timescales.

From left Mirjam, Michelle and Nicholas relaxed after the MSc defenses.

Mirjam Läderach has worked on “Continuous flow analysis on EastGRIP ice core: Optimization of optical dye method and results from acidity measurements on the EastGRIP ice core” where she successfully optimized an acid method for the determination of volcanoes in ice cores.

Michelle Shu-Ting Lee worked on “Climate proxies based on the NEEM ice core for the Holocene period 4000-7000 years B2K: An integrated CFA and IEC method for NEEM brittle zone”. The brittle zone is a zone in deep ice cores where continuous chemical sampling by CFA is not possible and thus time consuming discrete sampling combined with Ion Chromatography is required to obtain the chemical proxies for forest fire, volcanoes, wind and aridity.

And Nicholas Robles worked on “Spatial and Temporal Analysis of Greenland Shallow Snow Cores and HIRHAM5 Data”. He analysed the variability in several shallow snow cores covering only the past 5 years and compared the chemical results with weather data from climate modelling to generate a better understanding of the chemical proxies we use for the deep ice cores.

Congratulations to all 3.

The Olav Thon foundation supports a project on research-based teaching using Arctic fieldwork

The Ole Thon foundation supports Anne-Katrine Faber and Kerim Nisancioglu project “IceFinse – a field course on Arctic climate with focus on engaging students in research”. Picture by UiO/Terje Heiestad

by Anne-Katrine Faber & Kerim Nisancioglu

The Olav Thon Foundation recently announced the recipients of awards and financial support for research and teaching. Two ice2ice scientists from Bergen, Kerim Nisancioglu and Anne-Katrine Faber were awarded 1.5 mio NOK to their project IceFinse – a field course on Arctic climate with focus on engaging students in research”. 

The project aims to give Master level students first hand experience with Arctic research and fieldwork.  This course offer opportunities for learning that is not achieved in classical curriculum-based classes.  By giving students insight into  all steps of the research process, from formulation of a research question, to data collection and analysis and interpretation the course aims to engage students in research and prepare them to start working on their master thesis. This research-based field course on glaciology, ice cores and climate will be designed around the lecturers existing research. The studentdriven fieldwork and research projects will therefore contribute to ongoing research.

During the coming years they will develop and organize fieldwork courses at the research station at Finse in Norway  (https://www.finse.uio.no/) and the research station “Arktisk station”  (https://arktiskstation.ku.dk/).  at Disko Island in Greenland.

 The scientists officially received the financial support for their project at a  ceremony in Oslo on March 7th

New Ice2ice “not any more PhD” – Andreas Plach successfully defended his thesis

Andreas Plach successfully defended his thesis at the University of Bergen 5th March. The thesis is entitled “Simulation of the Eemian Greenland ice sheet“.

His supervisors has been Kerim Niscancioglu, Andreas Born (both University of Bergen) and Bo Møllesø Vinther (University of Copenhagen). The assessment committee consisting of Professor, ph.d. Anders Schomacker, Institutt for geovitenskap, Universitetet i Tromsø, Assistant Professor, ph.d. Miren Vizcaino, Department of Geoscience and Remote Sensing (GRS), Delft University of Technology, Nederland and Atle Nesje, Department of Earth Science, University of Bergen.

You can read more about the thesis here, unfortunately only in Norwegian.

Martin Olesen successfully defended his thesis

Martin Olesen successfully defended his thesis at the University of Copenhagen Monday 18th February. The thesis is entitled “High resolution climate simulation. Methods for improving and customising climate information with focus on outreach and uncertainty assessment”. His supervisors has been Jens H. Christensen, Peter Lang Langen and Eigil Kaas. The assessment committee consisting of Aslak Grinsted, Niels Bohr Institute, KU. Prof. Dr. Daniela Jacob, GERICS, Institute Helmholtz-Zentrum Geesthacht and Research Prof. Tim Carter, Finnish Environment Institute.

You Can read the abstract at the Niels Bohr Institute webpage

New Ice2ice PhD thesis “solves mysteries around large abrupt climate changes”

Henrik Sadatzki successfully defended his thesis for the PhD degree at the University of Bergen. The thesis is entitled: “Sea ice variability in the Nordic Seas over Dansgaard–Oeschger climate cycles during the last glacial – A biomarker approach

 

The last glacial period (ca. 10,000–100,000 years ago) was marked by repeated abrupt climate changes that had global implications. It is known from ice core records from the Greenland Ice Sheet that these glacial climate fluctuations comprised temperature shifts of up to 15°C over the Greenland ice sheet, happening within years or decades. These are the most prominent abrupt climate changes that we have recorded. While the underlying mechanisms of these so-called Dansgaard–Oeschger climate events are not yet fully understood, it is believed that changes in sea ice cover and ocean circulation in the Nordic Seas have played a key role in driving these enigmatic events.

In his studies, Sadatzki investigated the nature, timing and role of changes in sea ice cover in the Nordic Seas during several abrupt Dansgaard–Oeschger climate events ca. 30,000–40,000 years ago. For this purpose, he extracted and analyzed specific organic molecules from marine sediments, which were produced by certain sea ice algae and other phytoplankton thousands of years ago.

Sadatzki´s thesis documents sea-ice changes with an unprecedented detail, and show that in cold phases the sea ice cover was much more extended than today. The sea ice cover abruptly disappeared over large regions just prior to the abrupt warmings over Greenland. Abrupt changes in the sea ice cover thus have been important for creating the subsequent atmospheric changes.

The results support theories that have suggested that the sea ice cover changes were critical for the abrupt changes. Sadatzki´s work provides unprecedented proxy evidence of expansion and retreat of sea ice in the glacial Nordic Seas, contributing to an improved understanding of the role of sea ice changes in abrupt climate change in the past, and with relevance for the ongoing sea ice reduction in the Arctic today. The results are about to be published in leading international journals.

Ice2ice Phd Mads Bruun Poulsen succesfully defended his thesis on Parameterizing Southern Ocean eddy-induced circulation in coarse resolution ocean models.

Ice2ice Phd Mads Bruun Poulsen the 16/01-2019 successfully defended his PhD thesis on Parameterizing Southern Ocean eddy-induced circulation in coarse resolution ocean models. He was evaluated by an impressed committee consisting of Professor, Brian Vinter, eScience, Niels Bohr Institute, University of Copenhagen, Associate Professor, David Ferreira, Department of Meteorology, University of Reading, and Professor Joe LaCasce, Department of Geosciences, University of Oslo. He has been supervised by Markus Jochum from the Niels Bohr Institute.

Abstract: Baroclinic mesoscale eddies in the Southern Ocean induce a circulation which modulates wind-driven ventilation of the interior ocean, with implication for exchanges of heat and carbon dioxide with the atmosphere. In coarse resolution ocean general circulation models which do not explicitly resolve mesoscale eddies, eddy-induced circulation is typically parameterized with a skew-diffusive tracer flux that depends on an eddy transfer coefficient, κ. Several plausible closures for κ exist, yet consensus on a specific expression for κ remains largely absent in the ocean modeling community and results in uncertain Southern Ocean ventilation rate estimates. With the use of two ocean general circulation models of coarse and eddy-resolving horizontal resolution, this thesis assesses the properties of two recently proposed expressions for κ with the aim to provide guidance towards the optimal closure.

First an expression for κ which solely depends on local stratification is examined in a suite of model simulations with varying intensity of the zonal wind stress in the Southern Ocean. The simulations suggest that implementation of a dynamic κ alleviates coarse models from an overly sensitive overturning circulation although the parameterized eddy-induced circulation does not completely match that found in the eddy-resolving model. The latter shortcoming is associated with an overly strong poleward eddy heat transport in the coarse model, which is largely compensated by mean-flow heat transports. In addition, the coarse model demonstrates a centennial equilibration time scale to wind stress change that, if representative of the dynamics, has implication for evaluation of eddy compensation in eddying models.

Second, an expression for κ which additionally depends on eddy geometry and energy is investigated. It is shown that this closure derives from a correspondence between horizontal eddy buoyancy fluxes and variance ellipses, which offers a concise geometric interpretation of baroclinic mean-flow stability and vertical momentum transfers. The eddy geometry is examined in the eddy-resolving model to assess its potential to form basis for parameterization. The geometry obeys simple probability distributions and is insensitive to external forcing change, but also possesses vertical structure which relates to the orientation of horizontal eddy buoyancy fluxes with respect to the large-scale buoyancy gradient. This structure is not explained by rotational fluxes and hence represents a possible parameterization challenge.

The thesis also presents estimates of κ extracted directly from the eddy-resolving model and provides a discussion on the assumption of horizontally down-gradient eddy fluxes upon which the skew-diffusive tracer flux relies. In particular, this discussion reiterates a previous finding that a dynamically important component of the horizontal eddy buoyancy flux appears unaccounted for in coarse models.

Eystein Jansen receives the Brøgger prize!

Photo: Ronny Setså

During the annual Norwegian Geological Society winter conference held in Bergen this week Eystein Jansen was today awarded the Brøgger prize. The prize is the highest mark of honor a geologist can be given in Norway and is awarded to persons “…that have contributed in a unique way to understand especially the geology of Norway or geology in general” as written in the prize statutes.

The list of Eystein’s important scientific contributions given by the jury is very impressive; first the establishment of the Laboratory for geological mass spectronomy in Bergen in 1983, then the establishment and leadership in the Bjerknes Center for Climate Research (CoE) for 13 years starting in year 2000, his involvement in the establishment of the SapienCE – Centre for early human behavior (another CoE) in 2017, his contribution to the IPCC report and not at least his decisive role for the understanding the ocean circulation in the North Atlantic and link to the variation of ice sheets during the ice ages.

The fact that he has brought together geologists and modellers to better understand the climate system (as in Ice2ice) is also mentioned as an important contribution by the jury.

Congratulations Eystein!

You can read about Eystein and the award here, unfortunately only in Norwegian.