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High-resolution regional simulation of last glacial maximum climate in Europe
Swedish Meteorological and Hydrological Institute, Norrköping, Sweden.ORCID iD: 0000-0003-2689-9360
KTH, Stockholm, Sweden.
Swedish Meteorological and Hydrological Institute, Norrköping, Sweden.
Lund University, Geocentrum II, Lund, Sweden.
2011 (English)In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 63, no 1, 107-125 p.Article in journal (Refereed) Published
Abstract [en]

A fully coupled atmosphere–ocean general circulation model is used to simulate climate conditions during the last glacial maximum (LGM). Forcing conditions include astronomical parameters, greenhouse gases, ice sheets and vegetation. A 50-yr period of the global simulation is dynamically downscaled to 50 km horizontal resolution over Europe with a regional climate model (RCM). A dynamic vegetation model is used to produce vegetation that is consistent with the climate simulated by the RCM. This vegetation is used in a final simulation with the RCM. The resulting climate is 5–10 °C colder than the recent past climate (representative of year 1990) over ice-free parts of Europe as an annual average; over the ice-sheet up to 40 °C colder in winter. The average model-proxy error is about the same for summer and winter, for pollen-based proxies. The RCM results are within (outside) the uncertainty limits for winter (summer). Sensitivity studies performed with the RCM indicate that the simulated climate is sensitive to changes in vegetation, whereas the location of the ice sheet only affects the climate around the ice sheet. The RCM-simulated interannual variability in near surface temperature is significantly larger at LGM than in the recent past climate.

Place, publisher, year, edition, pages
John Wiley & Sons, 2011. Vol. 63, no 1, 107-125 p.
Keyword [en]
Climate, palaeo climate, climate model, LGM
National Category
Natural Sciences
Research subject
Meteorology
Identifiers
URN: urn:nbn:se:su:diva-123320DOI: 10.1111/j.1600-0870.2010.00485.xOAI: oai:DiVA.org:su-123320DiVA: diva2:873426
Available from: 2015-11-24 Created: 2015-11-24 Last updated: 2015-12-21Bibliographically approved
In thesis
1. High-resolution simulations of twocold palaeo climates in Europe: MIS 3 and LGM
Open this publication in new window or tab >>High-resolution simulations of twocold palaeo climates in Europe: MIS 3 and LGM
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The study of past climate is important because it increases our understandingof how the climate system works. Past climate is often reconstructed by us-ing proxies (that is observations of things that tell something about past cli-mate, for example tree rings, pollen in lake sediments and fossils). Modelsimulations of past climate further increases the knowledge since it has thepossibility to gap the space and time between the sparse and scattered proxyobservations, since a model simulation gives relatively continuous infor-mation about the whole simulated area. Model simulations can also giveinternally coherent information about parameters that is not easily recon-structed from proxies (for example heat fluxes).In this thesis two periods in the past are simulated by climate models: theMarine Isotope Stage 3 (MIS 3), 44 000 years ago, and the Last GlacialMaximum (LGM), 21 000 years ago. Both periods are characterised by lowtemperature, low sea level and low level of carbon dioxide. The topographyin northern Europe is dominated by ice sheets covering Iceland, Norway andparts of Sweden at MIS3; and more extensive ice sheets covering Iceland,Scandinavia, the British Isles and Northern Germany at LGM. These periodsare firstly simulated by a global climate model. Those simulations are subse-quently used in a regional climate model to increase the level of detail overEurope. To make the regional climate model simulation more realistic vege-tation simulated by a dynamical vegetation model is used in the regionalclimate model.The climate models simulate European climates much colder than today,especially at LGM. The temperature differences ranges from 5 to 45 °Ccolder than today; the largest differences being at the ice sheets where theperennial ice cover and the high altitude keep temperatures low. Precipita-tion is reduced with as much as almost 100 % in northern Europe due toreduced evaporation. Precipitation is increased with as much as 100 % inparts of southern Europe due to changes in atmospheric circulation. Thesimulations are in broad agreement with proxies, although there are differ-ences.The vegetation model simulates tundra like vegetation (herbs and shrubs) inthe ice-free parts of central and southern Europe. The eastern parts of Europeare dominated by needle-leaved trees. The short and cool summers limitvegetation. The simulated vegetation is in broad agreement with reconstruc-tions.Sensitivity studies of vegetation show that changed vegetation can changethe monthly mean temperature with 1-3 °C in some seasons and regions. Theresponse depends on regional surface characteristics. Sensitivity studies ofice sheets show that the simulated climate is consistent with the assumptionsabout the ice sheet extent made in the simulation. The simulated climate iscold enough in northern Europe to support the ice sheet, and warm enough insouthern Europe to prevent the ice sheet from expanding in this direction. Aremoval of the ice sheet would only have an effect on the local scale in thevicinity of the ice sheet, but this experiment did not include changes in thelarge-scale global atmospheric circulation.Although the regional climate model simulations are to a large degree de-pending on the global climate model simulations they provide new infor-mation. When comparing proxies with model data or studying local/regionalclimatic features (such as the interplay between climate and vegetation) highhorizontal resolution, as in the regional climate model, is important.

Place, publisher, year, edition, pages
Meteorologiska institutionen, 2015
Keyword
Palaeo climate, climate, climate model, proxy data, LGM, MIS 3
National Category
Meteorology and Atmospheric Sciences
Research subject
Meteorology
Identifiers
urn:nbn:se:su:diva-124347 (URN)
Presentation
2015-12-15, C609, 11:15 (English)
Opponent
Supervisors
Available from: 2015-12-21 Created: 2015-12-18 Last updated: 2015-12-21Bibliographically approved
2. High-resolution simulations of two cold palaeo climates in Europe: MIS 3 and LGM
Open this publication in new window or tab >>High-resolution simulations of two cold palaeo climates in Europe: MIS 3 and LGM
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The study of past climate is important because it increases our understanding of how the climate system works. Past climate is often reconstructed by using proxies (that is observations of things that tell something about past climate, for example tree rings, pollen in lake sediments and fossils). Model simulations of past climate further increases the knowledge since it has the possibility to gap the space and time between the sparse and scattered proxy observations, since a model simulation gives relatively continuous information about the whole simulated area. Model simulations can also give internally coherent information about parameters that is not easily reconstructed from proxies (for example heat fluxes).  In this thesis two periods in the past are simulated by climate models: the Marine Isotope Stage 3 (MIS 3), 44 000 years ago, and the Last Glacial Maximum (LGM), 21 000 years ago. Both periods are characterised by low temperature, low sea level and low level of carbon dioxide. The topography in northern Europe is dominated by ice sheets covering Iceland, Norway and parts of Sweden at MIS3; and more extensive ice sheets covering Iceland, Scandinavia, the British Isles and Northern Germany at LGM. These periods are firstly simulated by a global climate model. Those simulations are subsequently used in a regional climate model to increase the level of detail over Europe. To make the regional climate model simulation more realistic vegetation simulated by a dynamical vegetation model is used in the regional climate model.   The climate models simulate European climates much colder than today, especially at LGM. The temperature differences ranges from 5 to 45 °C colder than today; the largest differences being at the ice sheets where the perennial ice cover and the high altitude keep temperatures low. Precipitation is reduced with as much as almost 100 % in northern Europe due to reduced evaporation. Precipitation is increased with as much as 100 % in parts of southern Europe due to changes in atmospheric circulation. The simulations are in broad agreement with proxies, although there are differences.  The vegetation model simulates tundra like vegetation (herbs and shrubs) in the ice-free parts of central and southern Europe. The eastern parts of Europe are dominated by needle-leaved trees. The short and cool summers limit vegetation. The simulated vegetation is in broad agreement with reconstructions. Sensitivity studies of vegetation show that changed vegetation can change the monthly mean temperature with 1-3 °C in some seasons and regions. The response depends on regional surface characteristics. Sensitivity studies of ice sheets show that the simulated climate is consistent with the assumptions about the ice sheet extent made in the simulation. The simulated climate is cold enough in northern Europe to support the ice sheet, and warm enough in southern Europe to prevent the ice sheet from expanding in this direction. A removal of the ice sheet would only have an effect on the local scale in the vicinity of the ice sheet, but this experiment did not include changes in the large-scale global atmospheric circulation.  Although the regional climate model simulations are to a large degree depending on the global climate model simulations they provide new information. When comparing proxies with model data or studying local/regional climatic features (such as the interplay between climate and vegetation) high horizontal resolution, as in the regional climate model, is important.  

Abstract [sv]

Studiet av klimat i det förgångna är viktigt eftersom det ökar vår förståelse för hur klimatsystemet fungerar. Förgånget klimat rekonstrueras ofta med hjälp av proxies (det vill säga observationer av saker som säger något om klimatet förr i tiden, till exempel trädringar, pollen i sjösediment och fossiler). Modellsimuleringar av förgånget klimat ökar kunskapen ytterligare eftersom det ger en möjlighet att fylla i luckorna, i tid och rum, mellan de glesa och spridda proxy-observationerna, eftersom en modellsimulering ger information om hela det simulerade området. Modellsimuleringar kan också ge information om parametrar som inte så lätt rekonstrueras från proxies (till exempel värmeflöden).   I denna avhandling simuleras med klimatmodeller två perioder i det förgångna: MIS 3 (Marine Isotope Stage 3), för 44 000 år sedan och LGM (Last Glacial Maximum), för 21 000 år sedan. Båda perioderna kännetecknas av låg temperatur, låg havsnivå och låg halt av koldioxid. Topografin i norra Europa domineras av istäcken som täcker Island, Norge och Sverige vid MIS 3; och istäcken över Island, Skandinavien, Brittiska öarna och norra Tyskland vid LGM. Dessa perioder simuleras först av en global klimatmodell. Simuleringarna används senare i en regional klimatmodell för att öka detaljgraden över Europa. För att göra den regionala klimatmodell-simuleringen mer realistisk så används i den regionala klimatmodellen vegetation som är simulerad av en dynamisk vegetationsmodell. Klimatmodellerna simulerar europeiska klimat som är mycket kallare än dagens, särskilt vid LGM. Temperaturdifferensen spänner från 5 till 45 °C kallare än idag; de största skillnaderna är vid istäckena där det ständiga istäcket och den höga altituden håller temperaturen nere. Nederbörden minskar med så mycket som nästan 100 % i norra Europa på grund av minskad avdunstning. Nederbörden ökar med så mycket som 100 % i delar av södra Europa på grund av förändringar i atmosfärens cirkulation. Simuleringarna stämmer i stora drag överens med proxies, även om det finns skillnader.  Vegetationsmodellen simulerar tundralik vegetation (örter och snår) i de isfria delarna av centrala och södra Europa. De östra delarna av Europa domineras av barrträd. De korta och kalla somrarna begränsar vegetationen. Den simulerade vegetationen stämmer i stora drag överens med rekonstruktionerna. Känslighetsstudier av vegetationen visar att förändrad vegetation kan förändra månadsmedeltemperaturen med 1-3 °C i vissa regioner och under vissa säsonger. Responsen beror på regionala egenskaper vid markytan. Känslighetsstudier av istäckena visar att det simulerade klimatet är förenligt med de antaganden av istäckenas utbredning som görs i simuleringen. Det simulerade klimatet är tillräckligt kallt i norra Europa för att göra ett istäcke möjligt, och tillräckligt varmt i södra Europa för att hindra istäcket från att växa i den riktningen. Om istäcket skulle tas bort skulle det bara ha en effekt på lokal skala i närheten av istäcket, men detta experiment innefattade inte förändringar i atmosfärens cirkulation. Även om de regionala klimatmodell-simuleringarna till stor del beror på de globala klimatmodell-simuleringarna så ger de ny information. Vid jämförelser av proxies och modelldata eller studier av lokala/regionala egenskaper hos klimatet (som växelverkan mellan klimat och vegetation) så är hög horisontell upplösning, som i en regional klimatmodell, viktigt.

Place, publisher, year, edition, pages
Department of Meteorology, 2015. 28 p.
Keyword
Palaeo climate, climate modelling, proxy data, LGM, MIS 3
National Category
Natural Sciences
Research subject
Meteorology
Identifiers
urn:nbn:se:su:diva-123321 (URN)
Presentation
(English)
Opponent
Supervisors
Available from: 2015-12-21 Created: 2015-11-24 Last updated: 2015-12-21Bibliographically approved

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