Simulation into the future with a constant CO 2 concentration of 400 ppm

In the simulation of the future with a constant high CO2 concentration of 400 ppm, the

global climate is remarkably warmer than in the 280 ppm simulation (Figure 26b) and the ice sheet development is modest (Figure 26d). During the insolation minimum at about 17 kyr AP, which in the 280 ppm scenario caused a large ice sheet over Fennoscandia, in the 400 ppm simulations there is only some ice on the Scandinavian mountains. The next insolation minimum at about 54 kyr AP produces a small ice sheet from the Scandinavian mountains to Lapland and parts of Northern Ostrobothnia. This ice sheet retreats and Fennoscandia is almost ice-free in a climate slightly warmer than the present-day observed climate for the time period 65 kyr AP to 95 kyr AP. After 95 kyr AP a minor ice sheet starts to develop over the Scandinavian mountains, reaching Lapland around 100 kyr AP.

During the next 120 kyr the ice sheets do not reach Olkiluoto in the 400 ppm scenario. The mean temperatures at Olkiluoto are most of the time warmer than at present (+4 °C) (Figure 28). An exception is the insolation minimum at about 50 kyr AP, where the mean temperatures are about the same as at present (in the 280 ppm scenario, an extensive ice sheet development took place during this time). The monthly and annual total precipitation values are higher than in the present climate, but in general the variations in the annual precipitation rates during the next 120 kyr are small.

Figure 28. a) June solar insolation at 65° N, b) annual surface temperature around Olkiluoto downscaled with the GAM from the CLIMBER-2 future scenario with a 400 ppm CO2 concentration. c) The GAM downscaled mean annual total precipitation around Olkiluoto (downscaled from the CLIMBER-2 future scenario with a 400 ppm CO2 concentration).

6 DISCUSSION AND CONCLUSIONS

The aim of the present work is to formulate plausible future climate states at Olkiluoto, Finland on a regional scale, and especially to explore the possibility of extreme climatic conditions. For this purpose we used simulations performed with an EMIC model, CLIMBER-2 (Petoukhov 2000; Ganopolski 2001), coupled to the SICOPOLIS ice sheet model (Greve 1997; Calov 2005a). Three scenarios were explored in detail. The coldest of the scenarios was a simulation of the last glacial cycle, extending from 126 kyr BP until today, with the radiative forcing of atmospheric CO2, CH4 and N2O concentrations

derived from the Vostok ice core data (Ganopolski et al. 2010). The two other scenarios were simulations for the future. The colder one was a simulation of 120 kyr into the future with a constant CO2 concentration of 280 ppm. In the milder simulation the

corresponding CO2 concentration was 400 ppm (Potsdam Institute for Climate Impact

Research, Ganopolski et al. unpublished). The large-scale output of the CLIMBER-2 simulations was downscaled with a GAM-type regression model. We found that it was possible to choose the parameters in GAM so that the model performed well in three extremely different climate states over Fennoscandia. We were able to downscale monthly temperature and precipitation values for the full previous glacial cycle simulation as well as for the two future climate scenarios.

In the simulation of the last glacial cycle, large climatic variations occurred at Olkiluoto: a mild interglacial climate, a cold periglacial climate, a glacial climate with an ice sheet over the Olkiluoto area, and Olkiluoto submerged below sea level due to glacial load. The timings of the ice advances and retreats agreed with the paleoclimatic reconstructions on Northern Hemispheric scale, but there were differences between the simulated and reconstructed ice sheet extent over Northern Europe. Sensitivity studies showed that the simulated ice sheet evolution was sensitive to the model system’s surface energy and mass-balance interface and dust module. These sensitivities lead to uncertainties on the local extent of the simulated ice sheet. Therefore, in the simulations of the CLIMBER-SICOPOLIS model system the uncertainties about the location of the ice sheet margin are large, and in case an area is near the margin, it might as well be ice free as beneath the ice sheet.

In the CLIMBER-2-SICOPOLIS simulations into the future with a constant 280 ppm CO2 concentration, Northern Europe experienced three stadials with ice sheet advances

during the next 120 kyr. The first stadial started immediately during the next millennia with the coldest period occurring at 15-25 kyr AP. The second stadial occurred around 50–60 kyr AP. The third stadial, at around 90–100 kyr AP, was colder than the two previous ones, and during this the ice sheet over Olkiluoto was, at its thickest, about 1.7 km thick. Between the stadials, i.e., during the interstadials, the temperature conditions at Olkiluoto were near those of the present day. In the CLIMBER-2-SICOPOLIS simulation 120 kyr into the future with a constant 400 ppm CO2 concentration, a mild

interglacial climate prevailed throughout the simulation and no ice sheet existed in the vicinity of Olkiluoto.

A summary of the future simulations performed with CLIMBER-2 and other EMICs was presented in Chapter 2.2 in Table 3. All EMIC models (CLIMBER-2, MPM and

LLN-2D, MoBiDiC) brought out the feature that the onset of the next glaciation on the Northern Hemisphere is strongly dependent on the Earth’s orbital variations and on the atmospheric CO2 concentration. The CO2 concentration threshold required for the

immediate1 onset of the next glaciation varied from model to model. The CLIMBER-2- SICOPOLIS model system produced the onset of the next glaciation in Northern Europe and North America immediately with a CO2 concentration of 280 ppm. Cochelin et al.

(2006) showed, using the MPM model, that glacial inception could be immediate with pre-industrial levels of CO2 (240–270 ppm). Higher CO2 concentration levels (280–290

ppm) delayed the glacial inception to about 50 kyr from now. With the MPM model, even higher CO2 concentrations (>300 ppm) pushed the next glacial inception beyond

of the next 100 kyr period. The LLN-2D NH EMIC simulated an immediate onset of the next glaciation on the Northern Hemisphere only with CO2 concentrations of 230 ppm

or lower (Loutre & Berger 2000).

The modelling results of the EMICs clearly reveal the sensitivity of the models to the atmospheric CO2 concentration. The future atmospheric CO2 concentration will have a

crucial effect on the global climate. Present-day greenhouse gas concentrations are high in a glacial perspective, and will stay high for thousands of years (Archer 2005, Eby et al. 2009). With present-day greenhouse gas projections, the next glacial inception seems unlikely before 30 kyr AP. Hence, for the next 30 kyr the Earth’s climate will probably remain in an interglacial state. After 30 kyr the possibility of the onset of a glaciation increases, being highest during the Northern Hemisphere insolation minima at 50–60 kyr AP and 90–100 kyr AP. Nonetheless, sustained high atmospheric greenhouse gas concentrations might even further delay the onset of the next glacial period (Loutre & Berger 2000, Archer & Ganopolski 2005).

It remains impossible to predict future climate development exactly. Nonetheless, scenarios can be constructed. Kjellström et al. (2009) defined possible extreme climatic situations on the time-scale of 100 kyr. These extreme climatic situations were: a glacial climate, a periglacial climate and a climate warmer than at present. With the EMIC simulations 120 kyr into the future, we now estimate the potential time periods (or time windows) for these extreme climatic periods to occur over Fennoscandia and Olkiluoto. The simulations for the future show that insolation minima at 10–20 kyr AP, 50–60 kyr AP and 90–100 kyr AP hold a potential for cooling the climate in the Northern Hemisphere. The onset of a glaciation at 10–20 kyr AP is unlikely for the reasons mentioned earlier in this chapter (high atmospheric greenhouse gas concentrations and low eccentricity). However, the later two stadials hold a higher potential for the onset of a glaciation.

In the CLIMBER-2-SICOPOLIS 280 ppm scenario simulation, the CO2 level does not

decrease during glaciation, and hence the climate remains warmer during the stadials than in a realistic glaciation. We therefore suggest that for investigating the effects of a glaciation, data of the CLIMBER-2-SICOPOLIS last glacial cycle simulation should be used. For investigating the effects of a glaciation over the Olkiluoto region, the MIS 4 stadial ca. 70–60 kyr BP in the simulation is a glaciation lasting about 25 kyr, with the

1

here immediate onset of the next glaciation means that glaciers start to build up on the Northern Hemisphere during the next 10,000 years

ice sheet thickness reaching 2.5 km in that period. The area of Olkiluoto is depressed about 600 m. The simulated ice sheet retreated in about 8 kyr, which is comparable to the ice sheet retreat speed during the end of the last glaciation. A periglacial climate could occur at Olkiluoto between the stadials, in the period about 70–80 kyr AP. For investigating a periglacial climate, data for the MIS 3 (from 55kyr BP until 30 kyr BP), with a small ice sheet over Fennoscandia, is recommended to be used. Periglacial climate could occur at Olkiluoto during the stadials 50–60 kyr AP or 90–100 kyr AP also, if there was glaciation in Fennoscandia, but the ice sheet would not reach Olkiluoto. The Olkiluoto area could be near an ice sheet margin during a stadial as well as before and after a glaciation. For investigating climate near an ice sheet margin the data of the MIS 5b stadial about 93-85 kyr BP is recommended.

It is evident that, due to the ongoing global warming, the climate of the next centuries will be warmer and wetter than at present. For investigating a climate warmer than the present, the data of the 400 ppm CLIMBER-2 simulation is recommended. On the other hand, for investigating the effects of an extreme warm climate, we recommend that the data of the RCA3 regional model simulation with a CO2 concentration of 750 ppm be

used.

The delivered data is listed in Appendix 3.

It should be remembered that unpredictable events like super-volcanoes and meteorites are not considered in these scenarios. The present scenarios are based on the current best knowledge. The next step to improve glacial-scale (100 kyr) climate scenarios is the development of a fully coupled sophisticated climate-ice sheet-carbon cycle model.

7 ACKNOWLEDGEMENTS

We owe our gratitude to Andrey Ganopolski of the Potsdam Institute for Climate Impact Research for providing the climate simulations of CLIMBER-2-SICOPOLIS. Erik Kjellström and Gustav Strandberg of the Rossby Centre, Swedish Meteorological and Hydrological Institute, are acknowledged for the regional climate simulations with RCA3 model. We acknowledge Heikki Seppä from the Department of Geosciences and Geography, University of Helsinki for providing temperature and precipitation reconstructions for Northen Europe.

We acknowledge the Climate Research Unit for the 1961-1990 high-resolution temperature and precipitation data. CMAP Precipitation data were provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their Web site at http://www.esrl.noaa.gov/psd/

Elevation data were downloaded from the webpage of the National Geophysical Data Center, NOAA Satellite and Information Service

(http://www.ngdc.noaa.gov/mgg/gdas/gd_designagrid.html).

We acknowledge the contributors to the R project. The GAM fitting was done through the R software package “mgcv” downloaded from website of the R project for statistical computing (http://www.r-project.org/)

We acknowledge Kimmo Ruosteenoja from the Finnish Meteorological Institute, Heini Laine and Nuria Marcos from Saanio & Riekkola Oy, Ari Ikonen, Anne Lehtinen and Aimo Hautojärvi from Posiva Oy, and Erik Kjellström from the Swedish Meteorological and Hydrological Institute for providing valuable comments on the manuscript, and Robin King for language-checking.

REFERENCES

Anderson, P., Bermike, O., Bigelow, N., Brigham-Grette, J., Duvall, M., Edwards, M. E., Frechette, B., Funder, S., Johnsen, S., Knies, J., Koerner,R., Lozhkin, A., Marshall, S., Matthiessen, J., Macdonald, G., Miller, G., Montoya, M., Muhs, D., Otto-Bliesner, B., Overpeck, J., Reeh, N., Sejrup, H., Spielhagen, R., Turner, C. & Velichko, A. 2006. Last Interglacial Arctic warmth confirms polar amplification of climate change. Quaternary Science Reviews, 25, 1383–1400.

Archer, D. 2005. Fate of fossil fuel CO2 in geologic time. Journal of Geophysical

Research, 110, C09S05, doi:10.1029/2004JC002625.

Archer, D. & Ganopolski, A. 2005. A movable trigger: Fossil fuel CO2 and the onset of

the next glaciation. Geochemistry, Geophysic, Geosystems. 6, doi:10.1029/2004GC000891.

Archer, D. & Brovkin, V. 2008. The millennial atmospheric lifetime of anthropogenic CO2. Climatic Change, 90, 283-297.

Archer, D., Eby, M., Brovkin, V., Ridgwell, A., Cao, L., Mikolajewicz, U., Caldeira, K., Matsumoto, K., Munhoven, G., Montenegro, A. & Tokos, K. 2009. Atmospheric Lifetime of Fossil Fuel Carbon Dioxide. Annual Review of Earth and Planetary Sciences, 37, 117-134.

Arppe, L. & Karhu, J.A. 2006. Implications for the late Pleistocene climate in Finland and adjacent areas from the isotopic composition of mammoth skeletal remains. Palaeogeography, Palaeoecology, 231, 322-330.

Bamber J.L., Riva E.M.R., Vermeersen B.L.A & LeBrocq A.M. 2009. Reassessment of the Potential Sea-Level Rise from a Collapse of the West Antarctic Ice Sheet. Science, 342, 901-903.

Barnola, J.-M., Raynaud, D., Korotkevich, Y.S. & Lorius, C. 1987. Vostok ice core provides 160,000-year record of atmospheric CO2. Nature, 329, 408–414.

Barrows T.T., and Juggins S. 2005. Sea-surface temperatures around the Australian margin and Indian Ocean during the Last Glacial Maximum. Quaternary Science Reviews, 24, 1017–1047.

Berger, A. 1978. Long-Term variations of Caloric Insolation Resulting from the Earth’s orbital Elements. Quarternary Research, 9, 139–167.

Berger, A. & Loutre, M.F. 1991. Insolation values for the climate of the last 10 million years. Quaternary Science Reviews, 10, 297–317.

Berger, A. & Loutre, M.F. 2002. An exceptionally long interglacial ahead? Science, 297, 1287–1288.

Berger, A., Li, X.S. & Loutre, M.F., 1999. Modeling northern hemisphere ice volume over the last 3 million years, Quaternary Science Reviews, 18, 1–11.

Berger A., Loutre M.F. & Crucifix M. 2003. The Earth’s Climate in the Next hundred thousand years (100 kyr). Surveys of Geophysics, 24, 117–138.

BIOCLIM 2003. Deliverable D7: Continuous climate evolution scenarios over western Europe (1000km scale). http://www.andra.fr/bioclim/

BIOCLIM 2004. Deliverable D10 - 12: Development and Application of a Methodology for Taking Climate-Driven Environmental Change into Account in Performance Assessments. http://www.andra.fr/bioclim/

Björck, S. 1995. A review of the history of the Baltic Sea, 13.0–8.0 ka BP. Quaternary International, 27, 19–40.

Bonan, G.B., Levis, S., Kergoat, L. & Oleson, K.W. 2002. Landscapes as patches of plant functional types: An integrating concept for climate and ecosystem models. Global Biogeochemical Cycles, 16, 1021, doi:10.1029/2000GB001360.

Bonan, G.B. & Levis, S. 2006. Evaluating aspects of the Community Land and Atmosphere Models (CLM3 and CAM3) using a dynamic global vegetation model. Journal of Climate 19, 2290–2301.

Bradley, R.S. 1999. Paleoclimatology. Reconstructing Climates of the Quaternary, 2nd ed. International Geophysics Series, Volume 68. xv+613 pp. San Diego, London, Boston, New York, Sydney, Tokyo, Toronto: Academic Press.

Brovkin, V., Ganopolski, A. & Svirezhev, Y. 1997. A continuous climate-vegetation classification for use in climate-biosphere studies. Ecological Modelling, 101, 251–261. Calov, R., Ganopolski, A., Claussen, M., Petoukhov, V. & Greve, R. 2005a. Transient simulation of the last glacial inception. Part I: glacial inception as a bifurcation in the climate system. Climate Dynamics, 24, 545–561.

Calov, R., Ganopolski, A., Claussen, M., Petoukhov, V., Claussen, M., Brovkin, V. & Greve, R. 2005b. Transient simulation of the last glacial inception. Part II: sensitivity and feedback analysis. Climate Dynamics, 24, 563–576.

Cheng, M & Qi, Y. 2002. Frontal rain-fall rate distribution and some conclusions on the threshold method. Journal of Applied Meteorology, 41, 1128-1139.

Church, J.A. & White, N.J. 2006. A 20th century acceleration in global sea-level rise. Geophysical Research Letters, 33, L01602.

Claussen, M., Mysak, L., Weaver, A., Crucifix, M., Fichefet, T., Loutre, M.F., Weber, S., Alcamo, J., Alexeev, V., Berger, A., Calov, R., Ganopolski, A., Goosse, H., Lohmann, G., Lunkeit, F., Mokhov, I., Petoukhov, V., Stone, P. & Wang, Z. 2002.

Earth system Models of Intermediate Complexity: Closing the gap in the spectrum of climate system models, Climate Dynamics, 18, 579–586.

Cochelin, A.-S.B., Mysak, L.A. & Wang, Z. 2006. Simulation of long-term future climate changes with the green McGill paleoclimate model: The next glacial inception. Climatic Change, 79, 381–401, DOI 10.1007/s10584-006-9099-1

Collins, W.D., Bitz, C.M., Blackmon, M.L., Bonan, G.B., Bretherton, C.S., Carton, J.A., Chang, P., Doney, S.C., Hack, J.J., Henderson, T.B., Kiehl, J.T., Large, W.G., McKenna, D.S., Santer, B.D. & Smith, R.D. 2006.: The Community Climate System Model (CCSM3), Journal of Climate, 19, 2122–2143.

Crucifix, M., Loutre, M.F. & Berger, A. 2006. The climate response to the astronomical forcing. Space reviews, 125, 213–226.

Cuffey, K.M. & Marshall, S.J. 2000. Substantial contribution to sea-level rise during the last interglacial from the Greenland ice sheet. Nature, 404, 591–594. doi:10.1038/35007053.

Dahl-Jensen D., Mosegaard K., Gundestrup N., Clow G. D., Johnsen S. J., Hansen A. W. & Balling N. 1998. Past temperature directly from the Greenland Ice Sheet. Science, 282, 268–271.

Deblonde, G., Peltier, W.R. & Hyde, W.T. 1992. Simulations of continental ice sheet growth over the last glacial-interglacial cycle: experiments with one level seasonal energy balance model including seasonal ice albedo feedback. Global Planetary Change, 6, 37–55.

Denman, K.L., Brasseur, G., Chidthaisong, A., Ciais, P., Cox, P.M., Dickinson R.E., Hauglustaine, D., Heinze, C., Holland, E., Jacob, D., Lohmann, U., Ramachandran, S., da Silva Dias, P.L., Wofsy, S.C. & Zhang, X. 2007. Couplings between Changes in the Climate System and Biogeochemistry. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor & H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Dickens, G.R., Castillo, M.M. & Walkeret J.C.G., 1997. A blast of gas in the latest Paleocene: Simulating first order effects of massive dissociation of oceanic methane hydrate. Geology, 25(3), 259–262.

Eby, M., Zickfeld, K., Montenegro, A., Archer, D., Missner, K.J. & Weaver, A.J. 2009. Lifetime of Anthropogenic Climate Change: Millennial Time Sale of Potential CO2 and

Surface Temperature Perturbations. Journal of Climate, 22, 2501–2511.

Ehlers, J. & Gibbard, P.L. (Eds.) 2004. Quaternary glaciations – extent and chronology. Part I: Europe. Elsevier, 475 pp.

EPICA community members 2004. Eight glacial cycles from an Antarctic ice core. Nature, 429(6992), 623–628.

Eronen, M., 1990. Itämeren kehitys. In Alalammi, P. (ed). Atlas of Finland, Folio 123– 126: Geology, 15–18. National Board of Survey & Geographical Society of Finland, Helsinki.

Eronen, M., Glückert, G., van de Plassche, O., van der Plicht, J. & Rantala, P. 1995. Land uplift in the Olkiluoto-Pyhäjärvi area, south-western Finland, during the last 8000 years. Report YJT-95-17. Nuclear Waste Commission of Finnish Power Companies, Helsinki. 26 p.

Eronen, M. & Lehtinen, K. 1996. Description of the Quaternary geological history of Romuvaara, Kivetty and Olkiluoto sites (in Finnish with an English abstract). Posiva Oy, Eurajoki, Finland. Working Report PATU-96-74, 37 p.

Funder, S., Demidov, I. & Yelovicheva, Y. 2002. Hydrography and mollusc faunas of the Baltic and the White Sea-North Sea seaway in the Eemian. Palaeogeography,