Greenland Geothermal Heat Flow Database and Map (Version 1)

We compile and analyze all available geothermal heat flow measurements collected in and around Greenland into a new database of 419 sites and generate an accompanying spatial map. This database includes 290 sites previously reported by the International Heat Flow Commission (IHFC), for which we now standardize measurement and metadata quality. This database also includes 129 new sites, which have not been previously reported by the IHFC. These new sites consist of 88 offshore measurements and 41 onshore measurements, of which 24 are subglacial. We employ machine learning to synthesize these in situ measurements into a gridded geothermal heat flow model that is consistent across both continental and marine areas in and around Greenland. This model has a native horizontal resolution of 55ĝ€¯km. In comparison to five existing Greenland geothermal heat flow models, our model has the lowest mean geothermal heat flow for Greenland onshore areas. Our modeled heat flow in central North Greenland is highly sensitive to whether the NGRIP (North GReenland Ice core Project) elevated heat flow anomaly is included in the training dataset. Our model's most distinctive spatial feature is pronounced low geothermal heat flow (<ĝ€¯40ĝ€¯mWĝ€¯m-2) across the North Atlantic Craton of southern Greenland. Crucially, our model does not show an area of elevated heat flow that might be interpreted as remnant from the Icelandic plume track. Finally, we discuss the substantial influence of paleoclimatic and other corrections on geothermal heat flow measurements in Greenland. The in situ measurement database and gridded heat flow model, as well as other supporting materials, are freely available from the GEUS Dataverse (10.22008/FK2/F9P03L; Colgan and Wansing, 2021).publishedVersionPeer reviewe

Drumlin Formation Time: Evidence from Nothern and Central Sweden

Large-scale drumlins occur abundantly throughout central and northern Sweden. Whereas many drumlins in the north are an integral part of a relict glacial landscape > 100,000 years old, those to the south are generally interpreted as of last deglaciation age. Typically, the latter ones have not been overprinted by younger glacial landforms. Despite this apparent difference in formation history, drumlins in both regions have similar directional and morphological characteristics. A systematic analysis of >3000 drumlins in (i) areas within relief landscapes, (ii) areas with an ambiguous deglaciation age assignment, and (iii) areas within deglacial landscapes, indicates that these latter deglaciation drumlins differ clearly in both shape and size from drumlins in the other two types of landscapes. In addition, numerical modelling indicates that basal melting conditions, a prerequisite for drumlin formation, prevailed only for a very limited time over much of northern Sweden during the last deglaciation, but lasted for longer periods of time during earlier stages of the Weichselian. A reconnaissance radionuclide bedrock exposure date from the crag of a large drumlin in the relict landscape indicates that glacial erosion, and presumably drumlin formation, at this location predated Marine Isotope Stage 7. We conclude, therefore, that the large-scale drumlins of central and northern Sweden did not form during the last deglaciation, or during any other specific ice flow event. Instead, we suggest that they were formed by successive phases of erosion and deposition by ice sheets of similar magnitude and configuration

Drumlin formation time: evidence from Northern and Central Sweden

Large-scale drumlins occur abundantly throughout central and northern Sweden. Whereas many drumlins in the north are an integral part of a relict glacial landscape &#62;100,000 years old, those to the south are generally interpreted as of last deglaciation age. Typically, the latter ones have not been overprinted by younger glacial landforms. Despite this apparent difference in formation history, drumlins in both regions have similar directional and morphological characteristics. A systematic analysis of &#62;3000 drumlins in (i) areas within relict landscapes, (ii) areas with an ambiguous deglaciation age assignment, and (iii) areas within deglacial landscapes, indicates that these latter deglaciation drumlins differ clearly in both shape and size from drumlins in the other two types of landscapes. In addition, numerical modelling indicates that basal melting conditions, a prerequisite for drumlin formation, prevailed only for a very limited time over much of northern Sweden during the last deglaciation, but lasted for longer periods of time during earlier stages of the Weichselian. A reconnaissance radionuclide bedrock exposure date from the crag of a large drumlin in the relict landscape indicates that glacial erosion, and presumably drumlin formation, at this location predated Marine Isotope Stage 7. We conclude, therefore, that the large-scale drumlins of central and northern Sweden did not form during the last deglaciation, or during any other specific ice flow event. Instead, we suggest that they were formed by successive phases of erosion and deposition by ice sheets of similar magnitude and configuration

Simulated climate conditions in Europe during the Marine Isotope Stage 3 stadial

State-of-the-art climate models were used to simulate climate conditions in Europe during Greenland Stadial (GS) 12 at 44ka BP. The models employed for these simulations were: (i) a fully coupled atmosphere–ocean global climate model (AOGCM), and (ii) a regional atmospheric climate model (RCM) to dynamically downscale results from the global model for a more detailed investigation of European climate conditions. The vegetation was simulated off-line by a dynamic vegetation model forced by the climate from the RCM. The resulting vegetation was then compared with the a priori vegetation used in the first simulation. In a subsequent step, the RCM was rerun to yield a new climate more consistent with the simulated vegetation. Forcing conditions included orbital forcing, land–sea distribution, ice-sheet configuration, and atmospheric greenhouse gas concentrations representative for 44 ka BP. The results show a cold climate on the global scale, with global annual mean surface temperatures 51C colder than the modern climate. This is still significantly warmer than temperatures derived from the same model system for the Last Glacial Maximum (LGM). Regional, northern European climate is much colder than today, but still significantly warmer than during the LGM. Comparisons between the simulated climate and proxy-based sea-surface temperature reconstructions show that the results are in broad agreement, albeit with a possible cold bias in parts of the North Atlantic in summer. Given a prescribed restricted Marine Isotope Stage 3 ice-sheet configuration, with large ice-free regions in Sweden and Finland, the AOGCM and RCM model simulations produce a cold and dry climate in line with the restricted ice-sheet configuration during GS 12. The simulated temperature climate, with prescribed ice-free conditions in south-central Fennoscandia, is favourable for the development of permafrost, but does not allow local ice-sheet formation as all snow melts during summer

Summary of a workshop on extreme weather events in a warming world organized by the Royal Swedish Academy of Sciences

Climate change is not only about changes in means of climatic variables such as temperature, precipitation and wind, but also their extreme values which are of critical importance to human society and ecosystems. To inspire the Swedish climate research community and to promote assessments of international research on past and future changes in extreme weather events against the global climate change background, the Earth Science Class of the Royal Swedish Academy of Sciences organized a workshop entitled ‘Extreme weather events in a warming world’ in 2019. This article summarizes and synthesizes the key points from the presentations and discussions of the workshop on changes in floods, droughts, heat waves, as well as on tropical cyclones and extratropical storms. In addition to reviewing past achievements in these research fields and identifying research gaps with a focus on Sweden, future challenges and opportunities for the Swedish climate research community are highlighted