Walter Skinner

Summer Drought Patterns in Canada and the Relationship toGlobal Sea Surface Temperatures

Abstract Canadian summer (June–August) Palmer Drought Severity Index (PDSI) variations and winter (December– February) global sea surface temperature (SST) variations are examined for the 63-yr period of 1940–2002. Extreme wet and dry Canadian summers are related to anomalies in the global SST pattern in the preceding winter season. Large-scale relationships between summer PDSI patterns in Canada and previous winter global SST patterns are then analyzed using singular value decomposition (SVD) analysis. The matrix for the covariance eigenproblem is solved in the EOF space in order to obtain the maximum covariance between the singular values of the SST and the PDSI. The robustness of the relationship is established by the Monte Carlo technique, in which the time expansion of the primary EOF analysis is shuffled 1000 times. Results show that the leading three SVD-coupled modes explain greater than 80% of the squared covariance between the two fields. The interannual El Nino–Southern Oscillation (ENSO), the ...

The association between the BWA index and winter surface temperature variability over eastern Canada and west Greenland

Since about 1970, winter surface temperature data from stations on coastal eastern Canada and western Greenland have shown detectable decadal cooling. In this study, we attempt to understand some aspect of this surface cooling trend by relating it to the variability of the Canadian Polar Trough (CPT). In order to facilitate the relationship, we introduce a new 50 kPa index called the Baffin Island–West Atlantic (BWA) index which, although reflecting the variability of the western structure of the North Atlantic Oscillation (NAO), is found to explain temperature variability better in north-eastern North America than the structure characterized by the NAO index. The decadal variability in the winter surface temperature is found to be associated with the BWA index at a statistically significant correlation of 0·85. Two distinctive winter climate regimes are found to exist in the climate record from 1947 to 1995, one before and one after about 1970. Although the magnitude of the variance does not change significantly from one regime to the next, the two regimes are characterized by statistically significantly different means and by two distinct spectral signatures. Variability before 1970 is dominated by interannual fluctuations, whereas afterwards much of the contribution to the variability comes from interdecadal fluctuations. Subtraction of the 1947–1969 winter 50 kPa mean height field from the 1970–1995 mean field shows that the change in the height field over the Northern Hemisphere is reflected in the enhancement of the negative phase of the NAO mode (which corresponds to a strong jet stream over the western Atlantic and a strong Icelandic low) and of the positive phase of the Pacific/North America (PNA) mode.

Potential causes of differences between ground and surface air temperature warming across different ecozones in Alberta, Canada

Abstract Analysis and modelling of temperature anomalies from 25 selected deep wells in Alberta show that the differences between GST (ground surface temperature) warming for the northern Boreal Forest ecozone and the combined Prairie Grassland ecozone and Aspen Parkland transition region to the south occur during the latter half of this century. This corresponds with recent changes in surface albedo resulting from permanent land development in the northern areas and also to increases in natural forest fires in the past 20 years. Differences between GST and SAT (surface air temperature) warming are much higher in the Boreal Forest ecozone than in the Prairie Grassland ecozone and Aspen Parkland transition region. Various hypotheses which could account for the existing differences between the GST and SAT warming in the different ecozones of Alberta, and western Canada in general, are tested. Analysis of existing data on soil temperature, hydrological piezometric surfaces, snowfall and moisture patterns, and land clearing and forest fires, indicate that large areas of Alberta, characterised by anomalous GST warming, have experienced widespread changes to the surface landscape in this century. It is postulated that this has resulted in a lower surface albedo with a subsequent increase in the absorption of solar energy. Heat flow modelling shows that, after climatic SAT warming, permanent clearing of the land is the most effective and likely cause of the observed changes in the GST warming. The greater GST warming in the Boreal Forest ecozone in the latter half of this century is related to landscape change due to land development and increasing forest fire activity. It appears to account for a portion of the observed SAT warming in this region through a positive feedback loop with the overlying air. The anthropogenic effect on regional climatic warming through 20th century land clearing and landscape alteration requires further study. In future, more accurate quantification of these various forcings will be necessary in order to distinguish between, and to detect, the variety of natural and anthropogenic influences and on climate.

Large ground surface temperature changes of the last three centuries inferred from borehole temperatures in the Southern Canadian Prairies, Saskatchewan

Abstract New temperature logs in wells located in the grassland ecozone in the Southern Canadian Prairies in Saskatchewan, where surface disturbance is considered minor, show a large curvature in the upper 100 m. The character of this curvature is consistent with ground surface temperature (GST) warming in the 20th century. Repetition of precise temperature logs in southern Saskatchewan (years 1986 and 1997) shows the conductive nature of warming of the subsurface sediments. The magnitude of surface temperature change during that time (11 years) is high (0.3–0.4°C). To assess the conductive nature of temperature variations at the grassland surface interface, several precise air and soil temperature time series in the southern Canadian Prairies (1965–1995) were analyzed. The combined anomalies correlated at 0.85. Application of the functional space inversion (FSI) technique with the borehole temperature logs and site-specific lithology indicates a warming to date of approximately 2.5°C since a minimum in the late 18th century to mid 19th century. This warming represents an approximate increase from 4°C around 1850 to 6.5°C today. The significance of this record is that it suggests almost half of the warming occurred prior to 1900, before dramatic build up of atmospheric green house gases. This result correlates well with the proxy record of climatic change further to the north, beyond the Arctic Circle [Overpeck, J., Hughen, K., Hardy, D., Bradley, R., Case, R., Douglas, M., Finney, B., Gajewski, K., Jacoby, G., Jennings, A., Lamourex, S., Lasca, A., MacDonald, G., Moore, J., Retelle, M., Smith, S., Wolfe, A., Zielinski, G., 1997. Arctic environmental change of the last four centuries, Science 278, 1251–1256.].

ANOMALOUS GROUND WARMING VERSUS SURFACE AIR WARMING IN THE CANADIAN PRAIRIE PROVINCES

Modelling results of precision temperature logs made to depths of up to several hundred meters in numerous wells in the Canadian Prairie provinces (mostly Alberta) show evidence of average warming at the ground surface (GST) of 2.1 K (standard deviation = 0.9 K) mostly in the second half of this century. The GST warming signal for which higher frequency noise is cut off by the earth, which acts as a low-pass filter, correlates with the surface air warming (SAT) measured at screen level. A spatial comparison is made between the SAT warming and the GST warming for the last four decades in this region. A GIS (Geographic Information System) area cross tabulation was performed through the intersection of the classes of the ground and surface warming maps with a resulting contingency coefficient C= 0.805. Identical grid samples extracted from the ground warming and surface warming maps were related statistically with a resulting correlation coefficient of r= 0.75. Differences in the magnitudes of the warming exist due to the limited number of compatible data sets, errors in ground warming and air warming reconstructions, and land surface changes affecting the energy balance and subsurface heat fluxes. The influence of these effects requires further study. It is unlikely that all of the sites for which GST warming has been proven to correlate with air warming would have identical topography, vegetation, and hydrogeological disturbances for an area as large as the one under study (about 720,000 km2). The warming effect in the study area, as preserved by the ground, is mainly climate related.

Large ground warming in the Canadian Arctic inferred from inversions of temperature logs

Abstract The simultaneous functional space inversion applied for the first time to the set of precise temperature logs from 61 wells located between 60° and 82°N in northern Canada shows evidence of large ground surface temperature (GST) warming. These results include highest latitude locations of the well temperature profiles known in the Northern Hemisphere. There is strong evidence that GST warming started in the late-18th century and lasted until the 20th century. Simultaneous inversion of all well temperature data suggests that the cumulative ground surface temperature change over the past five centuries amounts to about 2°C significantly exceeding recent estimates from conventional climate proxies. This large GST warming is also present in other circumpolar locations in the Northern Hemisphere.

Prediction of Seasonal Forest Fire Severity in Canada from Large-Scale Climate Patterns

An empirical scheme for predicting the meteorological conditions that lead to summer forest fire severity for Canada using the multivariate singular value decomposition (SVD) has been developed for the 1953‐2007 period. The levels and sources of predictive skill have been estimated using a cross-validation design. The predictor fields are global sea surface temperatures (SST) and Palmer drought severity index. Two consecutive 3-month predictor periods are used to detect evolving conditions in the predictor fields. Correlation, mean absolute error, and percent correct verification statistics are used to assess forecast model performance. Nationally averaged skills are shown to be statistically significant, which suggests that they are suitable for application to forest fire prediction and for management purposes. These forecasts average a 0.33 correlation skill across Canada and greater than 0.6 in the forested regions from the Yukon, through northern Prairie Provinces, northern Ontario, and central Quebec into Newfoundland. SVD forecasts generally outperform persistenceforecasts. Theimportanceof the leadingtwo SVDmodesto Canadiansummerforestfire severity, accounting for approximately 95% of the squared covariance, is emphasized. The first mode relates strongly to interdecadal trend in global SST. Between 1953 and 2007 the western tropical Pacific, the Indian, and the North Atlantic Oceans have tended to warm while the northeastern Pacific and the extreme Southern Hemisphere oceans have shown a cooling trend. During the same period, summer forest fire exhibited increased severity across the large boreal forest region of Canada. The SVD diagnostics also indicate that the

Past surface temperature changes as derived from continental temperature logs-canadian and some global examples of application of a new tool in climate change studies

Abstract The application of well temperature profiles in the context of the recent global warming debate has been in use only for the last 18 years [Science 234 (1986) 689], but the influence of surface temperature variations due to climatic changes of all time scales on subsurface temperatures and heat flow variation with depth has been recognized for much longer [Bull. Geol. Soc. Am. 34 (1923) 703]. The borehole climate method is unique as it is based on the direct physical link between the measured temperature–depth profile and the reconstructed parameter of the past climate, the ground surface temperature (GST). It is unlike most of the other approximate methods of the past climate reconstruction. It has proved to be quite successful in reconstructing two robust signals: (a) the amplitude of the last glacial/interglacial temperature difference and (b) the surface temperature trend of the last 100–150 years and eventually, when combined with the surface air temperature series, in estimating their pre-observational means (POMs). A reconstruction of less robust signals of the little ice age, medieval climatic optimum, Boreal, Atlantic and possibly some other climatic periods of the Holocene fails even in most cases of purely conductive subsurface thermal regime. Borehole temperature profiles are not proxy for surface temperature, but a direct measure of the energy balance at the Earths continental surface. The signal underground is, however, attenuated considerably through heat diffusion. The degradation of the signal imposes a physical limit on the information potentially retrieved from the observed subsurface temperature anomalies. We describe the basic features and problems of the method of reconstruction of GST history from the temperature–depth profiles measured in boreholes which is illustrated by Canadian and other continental examples.

Western Canadian Sedimentary Basin temperature?depth transients from repeated well logs: evidence of recent decade subsurface heat gain due to climatic warming

Temperature versus depth measurements in boreholes on the Canadian Prairies were originally measured some two decades ago (1987). They were repeated a decade ago and were then repeated from 2005 to 2007. Modelling of the synthetic temperature?depth transients shows that the time variation of subsurface temperature follows variations in surface air temperature (SAT). The surface-temperature increases of 0.2 and 0.4 ?C are observed for time scales of one and two decades, respectively. The top of the atmosphere solar irradiance data recorded by satellite since 1978 was computed at the locations of the repeated temperature measurements to calculate a forcing signal to allow subsurface temperatures to be modelled, as previously done with SAT data. The mean sensitivity was assumed to be 1/(3???COS (latitude in degrees)???0.42) Wm2??C?1, which gives a sensitivity of 1.41?1.69 ?C Wm?2?at latitudes 49?52?N. While these sensitivity values correspond to equilibrium models in the transient times before the climate system reaches equilibrium, the temperature change is smaller and likely closer to 1 ?C Wm?2. Even for this higher mean sensitivity, the temperature response is not large enough to explain the ground surface temperature change. As SAT forcing explains the observed subsurface transients, factors other than solar forcing must be responsible for the observed large recent warming, likely anthropogenic changes related to the greenhouse effect.