THE CHANGING CLIMATE of FINLAND in Growth in Growth

International ConferenceEkaterinburg, 5-7 June 2006,5-7 inJune Ekaterinburg, 2006 Russia. Climate Changes and their impact on boreal temperate forests Mauri Timonen, Finnish Forest Research Institute, Rovaniemi Research Unit , Finland Kari Mielikäinen Finnish Forest Research Institute, Vantaa Research Unit, Finland Samuli Helama, Institute for Geology and Palaeontology, Johann Wolfgang Goethe University, 60325 Frankfurt am Main, Germany

THE LAST 1000 YEARS Mininimum years maximum years THE CHANGING CLIMATE OF FINLAND in growth in growth

Annual temperatures are generally rising in the The steady climate pattern in Finland is 1973 northern hemisphere, but the trend is not that explained by flat and low geography just beside 1963 1964 1960 clear in Finland if considered on a centennial the Scandinavian mountains, the atmospheric 1957 1940 scale. There was, first, an ascending trend from circulation (the prevailing positive NAO) and 1936 1930 1929 1927 the beginning of the 1900s to the mid-1930s, the warmth of Gulf Stream. This climatic 1926 1925 then followed by a descending trend up to the setting results in mean temperatures close to 1911 1903 1908 mid-1980s. Thereafter, an ascending trend has 1900 1901 long-term averages, mild winters, cool summers 1897 1900 1898 prevailed up to the present. The significance of and smaller in year-to-year variation. If the 1888 warming trend seems, however, to be less easterly winds would dominate in Finland, then 1873 significant as moving towards the north. summers would be warmer and winters colder. The temperature record of Sodankylä as well Tree-rings are an ultimate proxy tool for 1839 1840 1837 1838 as the tree-ring indices of Scots pine (Pinus 1836 providing past climate information. Metla, in 1825 sylvestris L.) indicate that global warming can- cooperation with the universities of Helsinki 1813 not so far been recognized as drastically elevat- 1806 1805 and Joensuu, completed in 1999 a 7520-year 1798 ing temperatures or tree-growths. The last seven 1790 1800 tree-ring chronology of timberline Scots pine. 1785 summers seem, however, to be warmer than the This record, now 7639 years long, is used as 1780 100-yr average of the record. Another interest- the main source in our studies of past climate 1769 ing issue is the rise of monthly minimum variations. 1747 1746 temperatures almost to the level of the 100-yr W e know now that ancient timberline was 1734 1736 average of the record. As a conclusion, the 100-200 m higher and even 80 km norther than 1728 1730 Finnish pine timberline continues its advancing 1718 today. Summer mean temperatures were, Modified by M. Timonen 2006 GOOGLE EARTH 2006 1708 1707 to the north and to higher altitudes. accordingly, 2 - 4 degrees warmer than today. 1696 1700 1694 Considering the causes of the current trend- 1688 1689 like warming, it is useful to look, how climate 1680 1679 varied during and after the warm and moist 1667 1668 1644 Atlantic period (ca. 7000 - 4500 years ago). 1642 1643 At that time, pine timberline reached its 1641 16321640 1633 1629 maximum appearance in Finnish Lapland. 1620 1621 1626 Obviously, the warmer summer climate of 1607 1601 1606 the Atlantic period did not cause any crucial 1593 1600 1594 1592 consequences, e.g. the melting of glaciers did 1579 The NAO phenomenon as well as the Gulf 1574 The North Atlantic Oscillation Stream are parts of the larger climatic sea water not cause any dramatic global climate cooling, 1575 circulation system called The Great Ocean Conveyer. W arm water flows from the south, comparable to 8.2k event. 1562 (NAO) and the Finnish climate heats the northern regions and then returns back to the south. This system is suspected to be vulnerable in global warming conditions. 1527 1528 The NAO plays a prominent role in the Finnish 1526 climate. This phenomenon at its active phase 1524 1523 forces moist and warm air of the Gulf Stream CLIMATIC TRENDS IN THE TIMBERLINE REGION 1516 1515 1517 spread to Finland, which results in warmer winters 1503 1514 and cooler summers. 2 Sodankylä 1500 1 1901-2005 1495 INTERPRETATION OF THE NAO-FIGURE 0 1485 F1 (cap, nose): Gulf Stream; -1 F2 (mouth/teeth): Midwinter (DJFM) NAO-indices; -2 F3 (right hand): Strong wintertime temperature- -3 o Sodankylä NAO correlation; Annual mean temperature -0.7 C 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 F4 (left hand): Strong summertime temperature- -6

NAO and statistically significant tree growth- -8 5-year means NAO correlation; -10 Mean of 1901-2005 F5 (stomach): Climatic influences affecting the -12 1430 timberline pine; -14 Monthly values F6 (right foot): NAOs impact on precipitation; -16 F1 Source: F2 F7 (left foot): NAOs impact on temperatures. -18 DJFM mean temperature -11.7 oC The Finnish Meteorological 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Institute (FMI) 16

15 1400 antic antic 14 h a c 13 NAO-index of JJA Nao index of JFM 2 12 4 0 11

2 o -2 June-July mean temperature 13.0 C 1364 0 1880 1900 1920 1940 1960 1980 10

-2 14 M ean temperature of J JA 13 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 -4 12 1347 11

M ean temperature of FM A 10 Growing seasons of Scots pine (June-July) have been close to -4 9 1338 -6 1337

-8 140 average during the last two decades. Midwinters (DJFM) were -10 120 1330 1331 100 -12 80 warm in the 1990s, but cool summers balanced the annual 1329 -14 Tree-ring index 1320 60 -16 1321 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 temperature again to be quite average.

1300 F3 F4 Veiksel ... Eem ... 1283 Quaternary ... Holocene ... 1279 Dendro- NAO chronology 1263 AO Tree-ring El Nino Proksit 1253 La Nina 1252 Chron- FlipFlop ology Greenhouse effect

Ice ages Subfossil 1230 Subfossiili 1229 1228 1221 1210 12001214

This 260-year timberline 1182 pine grows on the top of the 1180 Levi mountain. 1179 1174 1173 1175

F6 F7 1128 1125 1126 Timberline climate in the 1900s: precipitation Timberline climate in the 1900s: temperature 1119 O mm mm C o O mm January -14.0 C o C o 50 February 18 mm March 18 mm -6 O March -9.3 C 1112 January 22 mm 50 C February -13.7 C -4 50 -8 -6 1111 40 40 -8 -6 -10 1110 40 -10 1109 -12 -8 30 -12 30 1103 -14 -10 30 -14 1099 -16 20 -16 -12 20 1097 -18 1100 20 -18 1096 -14 10 -20 -20 10 -22 10 -16 1090 -22 -24 1089 0 -18 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 Vuosi Vuosi Vuosi Vuosi Vuosi Vuosi

O C o O o o mm April 20 mm May 25 mm June 47 mm April -3.3 C C May 3.1 C O C June 9.5 C mm mm 50 100 0 8 14 60 90

40 80 50 -2 6 12 70 40 60 30 -4 4 10 1064 50 30 1062 40 20 20 -6 2 8 30

10 20 10 0 6 10 -8 1053 0 1052 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 Vuosi Vuosi Vuosi Vuosi Vuosi Vuosi

m m July 61 mm mm August 60 mm mm September 44mm OC o O C o O C o 120 120 July 13.0 C August 10.7 C September 5.4 C 9 14 1038 100 16 100 100 8 13 80 80 80 14 12 7 1032 1027 60 60 60 11 6 12 1028 10 40 40 5 40

9 20 20 10 4 1022 20 8 1023 0 0 3 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 Vuosi Vuosi Vuosi Vuosi Vuosi Vuosi 1014 O O mm mm OC C C mm October 34 mm December 23 mm o -2 o o 60 November 29 mm 50 4 October -1.5 C November -8.0C December -12.1 C 100 -4 -4 2 -6 50 1000 80 40 -6 -8 0 40 -10 60 -8 30 -12 3 -2 30 -10 -14 40 20 -4 -12 h The tree-ring width curve after standardization -16 20 t 20 -6 -14 -18

10 10 -20 d and calibaration procedures tells about the -16 -8 0 -22 i 2 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 Vuosi 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 0 +40 Vuosi -40 -20 +20 Vuosi Vuosi Vuosi Vuosi June-July temperature variations

The whole year: 400 mm w June-July 108 mm mm December-March 81 mm mm O o mm C June-July 11.3 C O o O o 160 600 C December-March -12.3C C The whole year -1.7 C

200 15 1

-8 180 140 14

0 g 160 500 13 1 120 -10 Pointer years

140 n 12 -1 100 i 120 -12 400 11 100 80 -2 10 -14 R 80 60 300 9 -3 0 60 40 -16 8 40 -4 200 20 7 -18 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1500 1600 1700 1800 1900 2000 Vuosi Vuosi Vuosi Vuosi 1900 1920 1940 1960 1980 2000 Vuosi Vuosi A 7639-year chronology for Scots pine, Northern Finland, red line: 50-yr smoothed indices 150

100

-5500 -5000 -4500 -4000 -3500 -3000 -2500 -2000 -1500 -1000 -500 0 500 1000 1500 2000