scholarly journals Contrasting trends in floods for two sub-arctic catchments in northern Sweden – does glacier presence matter?

2012 ◽  
Vol 16 (7) ◽  
pp. 2123-2141 ◽  
Author(s):  
H. E. Dahlke ◽  
S. W. Lyon ◽  
J. R. Stedinger ◽  
G. Rosqvist ◽  
P. Jansson
Keyword(s):  
Air Temperature ◽  
Generalized Least Squares ◽  
The Arctic ◽  
Soil Water Storage ◽  
Trend Test ◽  
Glacier Mass Balance ◽  
Least Squares Regression ◽  
Northern Sweden ◽  
Extreme Precipitation Events ◽  
The Mean

Abstract. Our understanding is limited to how transient changes in glacier response to climate warming will influence the catchment hydrology in the Arctic and Sub-Arctic. This understanding is particularly incomplete for flooding extremes because understanding the frequency of such unusual events requires long records of observation not often available for the Arctic and Sub-Arctic. This study presents a statistical analysis of trends in the magnitude and timing of flood extremes and the mean summer discharge in two sub-arctic catchments, Tarfala and Abisko, in northern Sweden. The catchments have different glacier covers (30% and 1%, respectively). Statistically significant trends (at the 5% level) were identified for both catchments on an annual and on a seasonal scale (3-months averages) using the Mann-Kendall trend test. Stationarity of flood records was tested by analyzing trends in the flood quantiles, using generalized least squares regression. Hydrologic trends were related to observed changes in the precipitation and air temperature, and were correlated with 3-months averaged climate pattern indices (e.g. North Atlantic oscillation). Both catchments showed a statistically significant increase in the annual mean air temperature over the comparison time period of 1985–2009 (Tarfala and Abisko p<0.01), but did not show significant trends in the total precipitation (Tarfala p = 0.91, Abisko p = 0.44). Despite the similar climate evolution over the studied period in the two catchments, data showed contrasting trends in the magnitude and timing of flood peaks and the mean summer discharge. Hydrologic trends indicated an amplification of the streamflow and flood response in the highly glacierized catchment and a dampening of the response in the non-glacierized catchment. The glacierized mountain catchment showed a statistically significant increasing trend in the flood magnitudes (p = 0.04) that is clearly correlated to the occurrence of extreme precipitation events. It also showed a significant increase in mean summer discharge (p = 0.0002), which is significantly correlated to the decrease in glacier mass balance and the increase in air temperature (p = 0.08). Conversely, the non-glacierized catchment showed a significant decrease in the mean summer discharge (p = 0.01), the flood magnitudes (p = 0.07) and an insignificant trend towards earlier flood occurrences (p = 0.53). These trends are explained by a reduction of the winter snow pack due to higher temperatures in the winter and spring and an increasing soil water storage capacity or catchment storage due to progressively thawing permafrost.

scholarly journals Contrasting trends in hydrologic extremes for two sub-arctic catchments in northern Sweden − does glacier melt matter?

2012 ◽  
Vol 9 (1) ◽  
pp. 1041-1084 ◽  
Author(s):  
H. E. Dahlke ◽  
S. W. Lyon ◽  
J. R. Stedinger ◽  
G. Rosqvist ◽  
P. Jansson
Keyword(s):  
Air Temperature ◽  
The Arctic ◽  
Soil Water Storage ◽  
Glacier Mass Balance ◽  
Northern Sweden ◽  
Flood Events ◽  
Extreme Precipitation Events ◽  
Time Period ◽  
The Mean ◽  
Hydrologic Extremes

Abstract. It is not clear how climatic change will influence glacial meltwater rates and terrestrial hydrology in the Sub-Arctic and Arctic. This uncertainty is particularly acute for hydrologic extremes (flood events) because understanding the frequency of such unusual events requires long records of observation not often available for the Arctic and Sub-Arctic. This study presents a statistical analysis of trends in the magnitude and timing of hydrologic extremes (flood events) and the mean summer discharge in two sub-arctic catchments, Tarfalajokk and Abiskojokk, in northern Sweden. The catchments have different glacier covers (30% and 1%, respectively). Statistically significant trends (at the 5% level) were identified for both catchments on an annual and on a seasonal scale (3-months averages) using the Mann-Kendall trend test. Stationarity of flood records was tested by analyzing trends in the flood quantiles, using generalized least squares regression. Hydrologic trends were related to observed changes in the precipitation and air temperature, and were correlated with 3-months averaged climate pattern indices (e.g. North Atlantic Oscillation). Both catchments showed a statistically significant increase in the annual mean air temperature over the comparison time period of 1985–2009 (Tarfalajokk and Abiskojokk p < 0.01), but lacked significant trends in the total precipitation (Tarfalajokk p = 0.91, Abiskojokk p = 0.44). Despite the similar climate evolution over the studied time period in the two catchments, data showed contrasting trends in the magnitude and timing of flood peaks and the mean summer discharge. Hydrologic trends indicated an amplification of the hydrologic response in the highly glaciated catchment and a dampening of the response in the nonglaciated catchment. The glaciated mountain catchment showed a statistically significant increasing trend in the flood magnitudes (p = 0.04) that is clearly correlated to the occurrence of extreme precipitation events. It also showed a significant increase in mean summer discharge (p = 0.0002), which is significantly correlated to the decrease in glacier mass balance and the increase in air temperature (p = 0.08). Conversely, the nonglaciated catchment showed a significant decrease in the mean summer discharge (p = 0.01), the flood magnitudes (p = 0.07) and an insignificant trend towards earlier flood occurrences (p = 0.53). These trends are explained by a reduction of the winter snow pack due to higher temperatures in the winter and spring and an increasing soil water storage capacity or catchment storage due to progressively thawing permafrost.

Forest fires in the Muddus National Park (northern Sweden) during the past 600 years

1984 ◽  
Vol 62 (5) ◽  
pp. 893-898 ◽  
Author(s):  
Ola Engelmark
Keyword(s):  
Forest Fires ◽  
National Park ◽  
Pine Forests ◽  
The Arctic ◽  
Northern Sweden ◽  
Fire Scars ◽  
Dead Trees ◽  
Humus Layer ◽  
The Mean ◽  
Park Area

The occurrence of forest fires in the Muddus National Park (area, 50 000 ha), just north of the Arctic Circle in northern Sweden, was investigated on 75 separate sample plots. Between 1413 and the present, evidence of 47 fire years was obtained by dating the fire scars on living Scots pines (Pinus sylvestris), the oldest of which had germinated in 1274. The fire traces found on the sample plots were fire scars on living or dead trees or charcoal fragments in the humus layer. Plots lacking all traces of former forest fires were mainly those situated on sites surrounded by extensive mires. Forest fires were shown to have occurred in the five different types of forest investigated. The commonest frequencies of fires in the pine forests occurred with the interval 81–90 years, while the mean frequency was 110 years. The mean interval of time elapsed since the last forest fire occurred in the pine forests was 144 years. Some of the major fire years in the Muddus area coincide with forest fires in other parts of northern Sweden, in the taiga of western Russia, and in central Siberia.

scholarly journals Effect of atmospheric circulation on surface air temperature trends in years 1979–2018

2021 ◽  
Author(s):  
Jouni Räisänen
Keyword(s):  
Atmospheric Circulation ◽  
Air Temperature ◽  
Coupled Model ◽  
Surface Air Temperature ◽  
The Arctic ◽  
Mean Square ◽  
Temperature Trends ◽  
Mean Temperature ◽  
The Mean ◽  
Mean Square Difference

AbstractThe effect of atmospheric circulation on monthly, seasonal and annual mean surface air temperature trends in the years 1979–2018 is studied by applying a trajectory-based method on the European Centre for Medium-Range Weather Forecasts ERA5 reanalysis data. To the extent that the method captures the effects of atmospheric circulation, the results suggest that circulation trends only had a minor impact on observed annual mean temperature trends in most areas. Exceptions include, for example, a decrease in annual mean warming by about 1 °C in western Siberia, and increased warming in central Europe and the Arctic Ocean. However, the effect of circulation trends on seasonal and particularly monthly temperature trends is more substantial. Subtracting the effect of circulation changes from the ERA5 temperature trends leaves residual trends with a smoother annual cycle than the original trends. The residual monthly mean temperature trends also tend to agree better with the multi-model mean temperature trends from models in the 5th Coupled Model Intercomparison Project (CMIP5) than the original ERA5 trends do, with a 42% decrease in the mean square difference over the global land area. However, the corresponding decrease in the mean square difference of the annual mean temperature trends is only 6%.

scholarly journals A zero-power warming chamber for investigating plant responses to rising temperature

2017 ◽  
Vol 14 (18) ◽  
pp. 4071-4083 ◽  
Author(s):  
Keith F. Lewin ◽  
Andrew M. McMahon ◽  
Kim S. Ely ◽  
Shawn P. Serbin ◽  
Alistair Rogers
Keyword(s):  
Air Temperature ◽  
Electrical Power ◽  
Temperature Acclimation ◽  
The Arctic ◽  
Plant Responses ◽  
Control Chamber ◽  
Passive Warming ◽  
The Mean ◽  
Temperature Manipulation ◽  
The Impact

Abstract. Advances in understanding and model representation of plant and ecosystem responses to rising temperature have typically required temperature manipulation of research plots, particularly when considering warming scenarios that exceed current climate envelopes. In remote or logistically challenging locations, passive warming using solar radiation is often the only viable approach for temperature manipulation. However, current passive warming approaches are only able to elevate the mean daily air temperature by  ∼  1.5 °C. Motivated by our need to understand temperature acclimation in the Arctic, where warming has been markedly greater than the global average and where future warming is projected to be  ∼  2–3 °C by the middle of the century; we have developed an alternative approach to passive warming. Our zero-power warming (ZPW) chamber requires no electrical power for fully autonomous operation. It uses a novel system of internal and external heat exchangers that allow differential actuation of pistons in coupled cylinders to control chamber venting. This enables the ZPW chamber venting to respond to the difference between the external and internal air temperatures, thereby increasing the potential for warming and eliminating the risk of overheating. During the thaw season on the coastal tundra of northern Alaska our ZPW chamber was able to elevate the mean daily air temperature 2.6 °C above ambient, double the warming achieved by an adjacent passively warmed control chamber that lacked our hydraulic system. We describe the construction, evaluation and performance of our ZPW chamber and discuss the impact of potential artefacts associated with the design and its operation on the Arctic tundra. The approach we describe is highly flexible and tunable, enabling customization for use in many different environments where significantly greater temperature manipulation than that possible with existing passive warming approaches is desired.

scholarly journals The Average Environmental Efficiency Technique and its Application to Chinese Provincial Panel Data

2021 ◽  
Author(s):  
Jing Tang ◽  
Feng Yang ◽  
Fangqing Wei
Keyword(s):  
Central Area ◽  
Efficient Frontier ◽  
Generalized Least Squares ◽  
Mean Value ◽  
Environmental Efficiency ◽  
Least Squares Regression ◽  
Economic Openness ◽  
Significance Level ◽  
The Mean ◽  
National Environmental

Abstract In this study, we propose average environmental efficiency, a consistent and robust environmental efficiency measurement, and use it to evaluate the environmental efficiency of Chinese provinces. With the help of a nonparametric directional distance function approach, we can measure all possible environmental efficiency scores of the province by considering all projection directions to the efficient frontier. Then, the mean value of the environmental efficiency scores of a province in all possible projection directions is defined as the average environmental efficiency. Furthermore, we investigate the influencing factors of regional environmental efficiency via a feasible generalized least squares regression approach. The empirical results show that China’s national environmental efficiency has a high value of 0.803, and only nine provinces have average environmental efficiency greater than the average of the country. This implies that two-thirds of provinces still have much room for improvement. In addition, the east area achieved the best average environmental efficiency over the studied period, followed in order by the west area, central area, and northeast area. Moreover, we find that the energy consumption structure, government intervention, and economic openness negatively influence the regional environmental efficiency, while higher education positively influences this efficiency at the 1% significance level.

Do Changes in the Midlatitude Circulation Have Any Impact on the Arctic Surface Air Temperature Trend?

2006 ◽  
Vol 19 (20) ◽  
pp. 5422-5438 ◽  
Author(s):  
R. G. Graversen
Keyword(s):  
Air Temperature ◽  
Energy Transport ◽  
Surface Air Temperature ◽  
Arctic Region ◽  
Reanalysis Data ◽  
The Arctic ◽  
Positive Trend ◽  
Important Indicator ◽  
Near Surface ◽  
The Mean

Abstract The warming of the near-surface air in the Arctic region has been larger than the global mean surface warming. There is general agreement that the Arctic amplification of the surface air temperature (SAT) trend to a considerable extent is due to local effects such as the retreat of sea ice, especially during the summer months, and earlier melting of snow in the spring season. There is no doubt that these processes are important causes of the Arctic SAT trend. It is less clear, however, whether the trend may also be related to recent changes in the atmospheric midlatitude circulation. This question is the focus of the present paper. Model experiments have shown that in a warmer climate responding to, for example, a doubling of CO2, the atmospheric northward energy transport (ANET) will increase and cause polar SAT amplification. In the present study, the development of the ANET across 60°N and its linkage to the Arctic SAT have been explored using the ERA-40 reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF). It is found that during 1979–2001, the ANET has experienced an overall positive but weak trend, which was largest during the period from the mid-1980s to the mid-1990s. In addition, it is found that the Arctic SAT is sensitive to variability of the ANET across 60°N and hence to variability of the midlatitude circulation: A large ANET is followed by warming of the Arctic where ANET leads by about 5 days. The warming is located primarily north of the Atlantic and Pacific sectors, indicating that baroclinic weather systems developing around the Icelandic and Aleutian lows are important for the energy transport. Furthermore, it is suggested here that a small, but statistically significant, part of the mean Arctic SAT trend is linked to the trend in the ANET. Another important indicator of the midlatitude circulation is the Arctic Oscillation (AO). Through the 1980s and early 1990s the AO index has shown a positive trend. However, even though a part of the SAT trend can be related to the AO in localized parts of the Arctic area, the mean Arctic SAT trend shows no significant linkage to the AO.

scholarly journals A zero power warming chamber for investigating plant responses to rising temperature

2017 ◽  
Author(s):  
Keith F. Lewin ◽  
Andrew McMahon ◽  
Kim S. Ely ◽  
Shawn P. Serbin ◽  
Alistair Rogers
Keyword(s):  
Air Temperature ◽  
Electrical Power ◽  
Temperature Acclimation ◽  
The Arctic ◽  
Plant Responses ◽  
Control Chamber ◽  
Passive Warming ◽  
The Mean ◽  
Temperature Manipulation ◽  
The Impact

Abstract. Advances in understanding and model representation of plant and ecosystem responses to rising temperature have typically required temperature manipulation of research plots, particularly when considering warming scenarios that exceed current climate envelopes. In remote or logistically challenging locations, passive warming using solar radiation is often the only viable approach for temperature manipulation. However, current passive warming approaches are only able to elevate the mean daily air temperature by ~ 1.5 °C. Motivated by our need to understand temperature acclimation in the Arctic, where warming has been markedly greater than the global average and where future warming is projected to be ~ 2–3 °C by the middle of the century; we have developed an alternative approach to passive warming. Our Zero Power Warming (ZPW) chamber requires no electrical power for fully autonomous operation. It uses a novel system of internal and external heat exchangers that allow differential actuation of pistons in coupled cylinders to control chamber venting. This enables the ZPW chamber venting to respond to the difference between the external and internal air temperatures, thereby increasing the potential for warming and eliminating the risk of overheating. On the coastal tundra of northern Alaska our ZPW chamber was able to elevate the mean daily air temperature 2.6 °C above ambient, double the warming achieved by an adjacent passively warmed control chamber that lacked our hydraulic system. We describe the construction, evaluation and performance of our ZPW chamber and discuss the impact of potential artefacts associated with the design and its operation on the Arctic tundra. The approach we describe is highly flexible and tuneable enabling customization for use in many different environments where significantly greater temperature manipulation than that possible with existing passive warming approaches is desired.

scholarly journals A comparison between generalized least squares regression and top-kriging for homogeneous cross-correlated flood regions

2021 ◽  
Author(s):  
Simone Persiano ◽  
Jose Luis Salinas ◽  
Jery Russell Stedinger ◽  
William H. Farmer ◽  
David Lun ◽  
...  
Keyword(s):  
Least Squares ◽  
Generalized Least Squares ◽  
Least Squares Regression

scholarly journals Remote Sensing of Snow Cover Variability and Its Influence on the Runoff of Sápmi’s Rivers

Geosciences ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 130
Author(s):  
Sebastian Rößler ◽  
Marius S. Witt ◽  
Jaakko Ikonen ◽  
Ian A. Brown ◽  
Andreas J. Dietz
Keyword(s):  
Remote Sensing ◽  
Snow Cover ◽  
Air Temperature ◽  
Kendall Test ◽  
The Arctic ◽  
Boreal Winter ◽  
Snowmelt Runoff ◽  
River Catchment ◽  
Catchment Areas ◽  
Runoff Model

The boreal winter 2019/2020 was very irregular in Europe. While there was very little snow in Central Europe, the opposite was the case in northern Fenno-Scandia, particularly in the Arctic. The snow cover was more persistent here and its rapid melting led to flooding in many places. Since the last severe spring floods occurred in the region in 2018, this raises the question of whether more frequent occurrences can be expected in the future. To assess the variability of snowmelt related flooding we used snow cover maps (derived from the DLR’s Global SnowPack MODIS snow product) and freely available data on runoff, precipitation, and air temperature in eight unregulated river catchment areas. A trend analysis (Mann-Kendall test) was carried out to assess the development of the parameters, and the interdependencies of the parameters were examined with a correlation analysis. Finally, a simple snowmelt runoff model was tested for its applicability to this region. We noticed an extraordinary variability in the duration of snow cover. If this extends well into spring, rapid air temperature increases leads to enhanced thawing. According to the last flood years 2005, 2010, 2018, and 2020, we were able to differentiate between four synoptic flood types based on their special hydrometeorological and snow situation and simulate them with the snowmelt runoff model (SRM).

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