ANALYSIS OF CLIMATIC CHANGES IN THE SAN JUAN MOUNTAIN (SJM) REGION DURING THE 20 TH CENTURY Imtiaz Rangwala imtiazr@envsci.rutgers.edu MTNCLIM 2008 1
Objectives (as proposed) Nature of climate change in the SJM It s relationship to changes in the stream flow in the region To explore the mountains 2
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Kendall in the Wind[ow] 4
Overview Historical climate records for the SJM region Analysis of these records for the 20 th century - Temperature - Elevation Dependent Warming? (NWS vs SNOTEL) - Precipitation, SWE, Snowdepth Role of the Pacific Climate 5
Study Region COLORADO SJM 13 Counties 105.5-109 W and 37-38.5 N http://hprcc.unl.edu/ 6
Data Mining Monthly Avg. Temperature: NWS: (26), 1906-2005 SNOTEL (bigger (23) dataset since 1949) Precipitation: SNOTEL: NWS (22), started SNOTEL early (26) 1980s Snow water equivalent (SWE): SNOTEL (26), Since mid-1940s Snow Course (26) Snow-depth: Snow Course (26) JAN thru JUN Since mid-1940s and refining (esp. SNOTEL data) discarding impossible values filling in missing values 7
Temperature 8
Possible 2 o C warming between 1906-2005 Rapid warming between 1995 and 2005 Both NWS and SNOTEL sites confirm this trend NWS anomalies relative to 1960-1990 SNOTEL anomalies relative to 1990-2005 NWS vs SNOTEL r = 0.68 9
1950-2005 r = 0.94 10
SJM warming in context to warming elsewhere 11
CO division - 2 Div. 2 12
? 1950-2005 r = 0.84 13
NASA/GISS 14 http://data.giss.nasa.gov/gistemp/
At SJM: Surface warming twice that of global average Mid century cooling occurred later Late century warming started later too but happened more rapidly 1906-2005 r = 0.55 15
1906-2005 r = 0.56 16
Recent Decades 17
Trends based on the 5 o x 5 o gridded GHCN (Global Historical Climatology Network) land surface dataset provided by NCDC, NOAA 18
SJM: NWS vs SNOTEL SNOTEL sites 2500 ft higher than NWS sites Warming larger at SNOTEL than NWS except winter Spring and summer: Warming at least 2 times higher at SNOTEL Similar increases in T-max and T-min 19
Warming rates for 3 decades (C/decade) Large warming in 1995-2005 SNOTEL > NWS Similar increases in Max. T and Min. T during 1995-2005 particularly at SNOTEL sites 20
Warming rates for 3 decades (C/decade): Seasons 1995-2005: The decade of highest warming? Warming in all seasons at both sites Higher at SNOTEL except winter Very large during spring and summer at SNOTEL 21
Conclusions:Temperature The surface temperature in the SJM region may have increased by about 2 o C between 1906-2005 Half of this warming happened between 1990-2005; which is confirmed at both NWS and SNOTEL sites Temperature trends correlate well between NWS and SNOTEL sites More recent trends in warming in the San Juans appear to have started later than most other regions in the U.S. but has been more rapid 22
Broad temperature trend in the SJM is to similar to that of the contiguous US for the 20 th century Elevation dependency in local warming higher rates at SNOTEL sites 23
Snow 24
(Nov-May) Anomalies are normalized 25% decrease during 1995-2005 NWS vs SNOTEL r = 0.80 25
Snowfall And Snow-depth r = 0.87 25% decrease in snow-depth during 1995-2005 26
Snowfall And SWE 40% decrease in SWE during 1995-2005 Decrease in the total annual snow residence time Snowfall vs SWE: r = 0.83 SWE (Snow Course vs SNOTEL): r = 0.96 27
Snowfall And Snow-depth Decadal Average Snowdepth following snowfall trend 28
Snow-depth: Snow Course Sites Large snowdepth decreases in mid-late spring 29
Increase in Spring Melt? 30
Pacific climate indicies and the SJM climate 31
I-80 32
(+) ENSO and (+) PDO More Snowfall and Lower Winter Temperatures in the SJM 33
Pre-1975: Relationship exist but weak Post-1975: Breaks down; in fact becomes opposite? 34
Conclusions: Snow Rapid decreases in Snowfall (25%), SWE (40%) and Snowdepth (25%) at SNOTEL/Snow Course sites during the 1995-2005 period. These decreases in Snowfall cannot be explained by the traditional ENSO/PDO pattern. Large warming in spring and early summer can be related to the decreases in snow amount through the snow-albedo feedback mechanism Large decreases in SWE in spring may reflect in significant changes in the seasonal streamflow in the region. 35
Acknowledgements MSI mini-grant program Koren Nydick Jim Miller and Dave Robinson Rutgers Staff and Researchers at MSI People of Silverton DATA Sources 36
Thanks!!! 37
Is there a relationship? Rapid temperature increases And A rapid snow loss (In recent decades) 38
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1906-2005 r = 0.52 42
1906-2005 r = 0.52 43
Monsoon Precipitation No long term trends NWS vs SNOTEL r = 0.91 However, a sharp decrease between 1995-2005 44