Camille Li and Andreas Born will present their newest paper “Coupled atmosphere-ice-ocean dynamics in Dansgaard-Oeschger events“ and we will have the opportunity to discuss with them. You can find the paper here; https://www.sciencedirect.com/science/article/pii/S0277379118305705
After the presentation and discussion, we will have a small Christmas event and serve you gløgg and something sweet to eat. Please indicate here if you want to join in, before Friday 30.11 at 12.
The Dansgaard-Oeschger events of the last ice age are among the best studied abrupt climate changes, yet a comprehensive explanation is still lacking. They are most pronounced in the North Atlantic, where they manifest as large temperature swings, on timescales of decades or shorter, between persistent cold (stadial) and warm (interstadial) conditions. This review examines evidence that Dansgaard-Oeschger events are an unforced or “spontaneous” oscillation of the coupled atmosphere-ice-ocean system comprising the North Atlantic, Nordic Seas and Arctic, collectively termed the Northern Seas. Insights from reanalysis data, climate model simulations, and idealized box model experiments point to the subpolar gyre as a key coupling region where vigorous wind systems encounter the southernmost extension of sea ice and the most variable currents of the North Atlantic, with connections to the deep ocean via convection. We argue that, under special conditions, these components can interact to produce Dansgaard- Oeschger events. Finding the sweet spot is a matter of understanding when the subpolar region enters a feedback loop whereby changes in wind forcing, sea ice cover, and ocean circulation amplify and sustain perturbations towards cold (ice-covered) or warm (ice-free) conditions. The resulting Dansgaard-Oeschger-like variability is seen in a handful of model simulations, including some “ugly duckling” pre-industrial simulations: these may be judged as undesirable at the outset, but ultimately show value in suggesting that current models include the necessary physics to produce abrupt climate transitions, but exhibit incorrect sensitivity to the boundary conditions. Still, glacial climates are hypothesized to favour larger, more persistent transitions due to differences in large-scale wind patterns. Simplified models and idealized experimental setups may provide a means to constrain how the critical processes act, both in isolation and in combination, to destabilize the subpolar North Atlantic.
Low-latitude climate variability during the late Quaternary and teleconnections to high latitudes
Time: Mandag 21. januar 2019, kl. 10.15
Venue: Auditorium 4, Realfagbygget
Forsker Anna Nele Meckler, Institutt for geovitenskap
Professor Haflidi Haflidason, Institutt for geovitenskap
Professor Kerim Hestnes Nisancioglu, Institutt for geovitenskap
MSc. Henrik Sadatzki will defend his ph.d.
Time: Friday 15. February, at 10.15h
Venue: Auditorium 4, Realfagbygget
Titel of the thesis:
Sea ice variability in the Nordic Seas over Dansgaard–Oeschger climate cycles during the last glacial – A biomarker approach
Professor, ph.d. Jerry McManus
Department of Earth and Environmental Sciences,
Columbia University, Lamont-Doherty Earth Observatory, USA
Førsteamanuensis, ph.d. Christof Pearce
Department Of Geoscience, Aarhus University, Danmark
Member in the comitee:
Førsteamanuensis, ph.d. Anna Nele Meckler
Institutt for geovitenskap, Universitet i Bergen
Martin Olesen will be having his PhD defense on Monday 18 February at 9:15, in room 008, Tagensvej 16.
Martin´s PhD thesis is titled: High resolution climate simulation. Methods for improving and customising climate information with focus on outreach and uncertainty assessment.
Abstract: Application of a single high resolution regional climate model (RCM) simulation for Greenland implies detailed information on the model performance compared to in situ observations and other RCMs. Projections of future climate change based on an ensemble of climate models are more robust than estimates based on a single model. In this thesis a statistical method to better frame results based on the RCM HIRHAM5 is utilized to assess uncertainties of projected climate change results. Expected future climate changes and associated uncertainties in Greenland are estimated for the periods 2031-2050 and 2081-2100. This analysis is based on HIRHAM5 at a horizontal resolution of approximately 5.5 km, emission scenarios used by IPCC and on European regional climate studies (EURO-CORDEX). Using HIRHAM5 simulations over Greenland in combination with an ensemble of coarser RCM simulations from a different geographical setting; EURO-CORDEX, we investigate to what extent the uncertainty of projected high-resolution climate change can be evaluated from corresponding temperature spread in a wider set of global climate models (GCMs), CMIP5. Furthermore, HIRHAM5 is compared with in situ observation records through spatially linked correlated patterns for temperature and precipitation. Improved climate information is achieved by combining long weather records from the Greenlandic coastal stations and proxy measurements of temperature and solid accumulation from deep ice cores and HIRHAM5 simulations. HIRHAM5 provides physically consistent information of temperature, precipitation, snow fall, melt, evaporation and surface mass balance (SMB) for the period 1980-2014. Our proposed uncertainty assessment method establishes a foundation on which high-resolution and relative costly regional climate projections in general can be assessed. Also when using only a single RCM without the presence of analogous downscaling experiments with other RCMs and GCMs, the uncertainty assessment is relying on already existing information from CMIP5. Thus, the uncertainty of a wide range of climate indices that scale with temperature can be evaluated and quantified through the inter-model temperature spread within CMIP5. Changes in growing season, number of frost days and consecutive dry days are presented as index examples. This investigation shows with high confidence that HIRHAM5 is representative of the ensemble of RCMs within EURO-CORDEX. By relating large scale correlations of various climate variables deduced from HIRHAM5, observed temperature and precipitation in situ records are prolonged 500 years back in time based on proxy data from deep ice cores. SMB for selected drainage basins on the Greenland ice sheet and for the Renland ice cap are reconstructed and show decreasing trend lines towards present. The SMB for the drainage basin nearest Tasiilaq, decreases from + 0.5 mm weq/yr for 1898-2014 to -5.4 mm weq/yr in 1980-2014. Correspondingly, the SMB for the drainage basin nearest Danmarkshavn decreases from -0.3 mm weq/yr for 1950-2014 to -1.1 mm weq/yr in 1980-2014, and the SMB of the Renland ice cap decreases from +2.4 mm weq/yr for 1950-2007 to -4.7 mm weq/yr in 1980-2007. Finally, the correlation patterns of temperature and precipitation illustrate the coverage of correlated weather stations and ice core drill site locations across Greenland. In situ observation records reflect with high confidence the spatial correlation patterns calculated from HIRHAM5 for both temperature and precipitation.
Prof. Jens Hesselbjerg Christensen, Physics of Ice, Climate and Earth, Niels Bohr Institute, University of Copenhagen
Prof. Eigil Kaas, Physics of Ice, Climate and Earth, Niels Bohr Institute, University of Copenhagen
Peter Lang Langen, Research and Development, Danish Meteorological Institute
Aslak Grinsted, Physics of Ice, Climate and Earth, Niels Bohr Institute
Prof. Dr. Daniela Jacob, GERICS, Institute Helmholtz-Zentrum Geesthacht
Research Prof. Tim Carter, Finnish Environment Institute
A small workshop with the aim to synthesize marine and ice core data using the new MIS 3 tephra synchronisation points and discuss possible timings, a sort of follow up on the DO meeting we had in 2016.
–Draft ERC Budget tables
–Draft Form C completed in the portal if possible
–Work force table (final)
Here is the press release from the thesis.
Lisa and Sunniva will present new data.
We will have a short Ice2ice Bergen meeting before lunch this Friday presenting the format of the final all-staff meeting in May.
Sandwiches will be served after the meeting.