Climate change and its geophysical and ecological impacts in the Swedish Sub-

Arctic Mountains

Terry Callaghan The Royal Swedish Academy of Sciences’

Abisko Scientific Research Station and Friends

The mountainous Abisko area compresses long latitudinal gradients

Taiga

Forest-tundra

Alpine

And much of the landscape is a complex mosaic of plant communities

alpineheath

birch forestmire lake

river

aspen

pine

shrubs

Initial estimates of carbHeaths dominate the area but birch forest is the dominant carbon sink in most years (and water is a source):

Christensen et al., 2007

Multiple accelerating environmental changes

1920 1930 1940 1950 1960 1970 1980 1990 2000-3

-2

-1

0

1

2

Mea

n te

mpe

ratu

re (°

C)

ANS annual mean

Gauss(9)Gauss(3)

Increased by > 1deg C

-4.0

-2.0

0.0

2.0

1900 1920 1940 1960 1980 2000 2020

Air

tem

pera

utre

(¡C

)

Temperature has changed abruptly.

Summary of temperature changes

Mean annual temperature has risen significantly since the peak of the 1930’s by 0.9 deg C to above zero: it is warmer now than probably in the last 1000 years

Spring temperatures have increased steadily

Summer has become warmer than average for 11 consecutive years since 1995

Autumn has become hotter since 1999 as an abrupt change

Very cold winters have been absent since 1988

Mean annual, spring and autumn temperatures are accelerating

Ipcc veg slide etc

Sami

0102030405060708090

100

1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

MAM m

ean

snow

depth (cm)

MSEP

c)

Snow depth has increased by 2 to 3 cm per 10 years

Changing snow conditions : depth almost doubled in 90 years

Kohler et al., 2006;

1960 1970 1980 1990 2000 20100

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5Snow layer closest to ground

year

Dry

ness

wet

dry

Hard ice

Soft snow

Hardness of bottom layer Wetness of bottom layer

Some snow characteristics are changing down the profile

C. Johansson et al., in prep.

Picture: Johannes Förster

Maximum ice thickness

60

80

100

120

Thic

knes

s (c

m)

Number of days with ice

110

160

210

Day

s

Date of freeze and break up

11-nov

31-dec

19-feb

10-apr

30-maj

19-jul

1912 1922 1932 1942 1952 1962 1972 1982 1992 2002

Date 197 days 130 days

- 5.7 cm in 50 years

- 13 days in 100 years

8 days later

8 days later

6 days earlier 6 days earlier

Lake ice cover is decreasing: ca. 2 weeks in 90 years

Year

Dev

iatio

n

Dev

iatio

nUV-B radiation increased by 11% between 1950 and 1999: absorbtion by ice-free lake water will be much greater

Lindfors et al., 2007

Permafrost is melting at low altitude Permafrost is melting at low altitude in the Abisko areain the Abisko area

The active layer thickness at sites along a transect has increased considerably between 1978 and 2006

Åkerman and Johansson In press.

Perma- frost

Active layer

Act

ive

laye

r dep

th 4

0-90

cm

Thawing permafrost is changing hydrology, vegetation and methane emissions

( Christensen et al., 2004, Johansson et al., 2007

Shrub and forest growth is increasing: treeline has increased at 5 m per 10 yr, = 40 m per deg C summer air temperature

increase (Callaghan et al., 2004)

Lapland

1937

1959

Pålnoviken1906

Emanuelson, 1987

1986

Autumn moth eggs survive if winter temperatures do not drop below -360C and cold winters are becoming fewer

Autumn and winter moths and warming are changing the forest

van Bogaert et al., submitted

Aspen is now found in some places which have warmed and where there is disturbance. Many young trees are found at and beyond the birch treeline

In 3 weeks, autumn moths can convert forest from being a carbon sink to a carbon source: T. Johansson et al., in review

Outbreak site 1

Before outbreak site 1Slight outbreak, site 2

No outbreak, site 2

Carbon source

Carbon sink

< 10th January 2001, temp. -20

0C

17th January 2001, temp.

+50C >

Extreme events are increasing: 1913-2000, 1 major winter warming event each year, 2000-2008, 1 major event each year

Snow and ice: traditional reindeer husbandry knowledge helps refine experiments that explain natural events A few warm days in winter have long-lasting effects

Bokhorst et al., in press May 2008

Snow and ice: traditional reindeer husbandry knowledge helps refine experiments winter warming experiment

May 2008

Extreme precip. – precip. on days with > 20 mm/day

Extreme precipitation events cause infras- tructure damage and geomorphological changes already: the future could be dangerous!

?

Changes in vegetation

The ways forward: modelling the Barents Region from a modified LPJ-GUESS model: but how do we include

the actual complexity? Wolf et al., 2008

Productivity

Re-inventing climate change impact science: modelling within the local

perspective for adaptation

Conclusions

Thank you for your attention

Overall, too many surprises are happening – our predictive and observational powers are too low.

In sub-Arctic Sweden, environmental change is not only happening, it is acceleratingCrossing thresholds such as 0oC and lack of cold winters have large effects

Disturbance + warming lead to abrupt changes

Extreme events in winter are increasing and have impacts in the following summer and for many decades beyond

Prediction is difficult –

monitoring is essential