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Workreport 2018-9

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Name:

Climate Projections for Olkiluoto

Writer:

Thölix, L., Korhonen, H., Ruosteenoja, K.

Language:

English

Page count:

120

Summary:

The future evolution of climate in the Olkiluoto region was investigated in the time scales of 130, 10,000, 120,000 and 1,000,000 years by analysing results from the Coupled model intercomparison project (CMIP3 and CMIP5) as well as by making new climate model runs with the CLIMBER-2-SICOPOLIS model. The future climate depends strongly on the CO2 concentration and therefore different CO2 scenarios based on RCP scenarios and existing literature data were used to scope the potential future climate developments. Using the constructed scenarios, changes in temperature, precipitation, humidity, wind speed and radiation as well as sea level height and ice thickness were calculated for the Olkiluoto region.

According to different CMIP scenarios, the temperature in Olkiluoto will rise by 2 °C - 6 °C by the end of the century compared to present day values. The annual precipitation is projected to increase by 7 - 18%, i.e., the climate is turning wetter. More extreme precipitation events are also expected. Changes in both temperature and precipitation are expected to be stronger in winter than in summer. The projections of sea level rise close to Olkiluoto are rather uncertain, mainly due to the high uncertainty concerning the melting rate of the Greenland and Antarctic ice sheets. The current best estimate is that in the Olkiluoto region land uplift will dominate over the sea level rise throughout the 21st century. The projected local change in Rauma between years 2000 and 2100 is between -42 cm and 54 cm.

Beyond the 21st century, it was found that the projected changes in climatic variables depend strongly on the magnitude of anthropogenic greenhouse gas emissions and the assumed decline rate of CO2 – both of these aspects have currently high uncertainties. During the next 10 kyr, the simulated maximum annual mean temperature change in Olkiluoto is -2 °C – +9.5 °C. The strongest warming is projected under RCP8.5 followed by slow CO2 decline, and RCP2.6 with fast CO2 decline could result to cooling compared to present day. In the 10-kyr simulations, the projected annual total precipitation changes in Olkiluoto remain below 17% under all scenarios apart from RCP8.5, where it is 30%. Under most scenarios precipitation increases. The overall changes for the other atmospheric parameters investigated (wind speed, relative humidity, net surface radiation) are small, and thus likely within the current uncertainty range. The extent of the Fennoscandian ice sheets in the next 10 kyr depends strongly on both the RCPs and the decline rate of CO2 after the emission peak. The ice sheet does not reach Olkiluoto

During the next 120 kyr, orbital forcing would allow for the onset of at least three glaciation periods with potential of ice sheets reaching Olkiluoto: about 20 kyr, 60 kyr and 100 kyr AP. However, the atmospheric CO2 concentration has to decline close to or below 300 ppm to enable ice in Olkiluoto in the next 120 kyr. Under the RCP8.5 scenarios Olkiluoto stays without ice the next 120 kyr, whereas under RCP2.6 with fast CO2 decline ice is reaching Olkiluoto before 15 kyr AP.  Glacial onsets can be seen in meteorological parameters. Annual mean temperature change is large during glacial periods and smaller between them. The annual mean precipitation, wind speed and net surface radiation time series for the different scenarios look qualitatively very similar to the corresponding temperature series. The projected changes in relative humidity are small except during glacial periods. Differences between winter and summer changes are remarkable for radiation, wind speed and relative humidity.

In the 1,000,000 year simulations, the evolution of climate in Olkiluoto region was simulated by accounting only for natural climate forcings and prescribing CO2 concentration according to the RCP8.5 scenario. After 150 kyr AP the two simulations had almost identical CO2 concentrations, and therefore no additional long simulations needed to be made. The simulated Fennoscandian ice volume anticorrelates with June insolation.

Keywords:

Climate evolution, climate predictions, CLIMBER-2-SICOPOLIS, glaciation

File(s):

WR 2018-09_web (pdf) (55.7 MB)


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