Wind speed extremes in the sub-Arctic realm of the North-East Pacific region were investigated through extreme value analysis of wind speed obtained from wind simulations of the COSMO-CLM (Consortium for Small-scale M...Wind speed extremes in the sub-Arctic realm of the North-East Pacific region were investigated through extreme value analysis of wind speed obtained from wind simulations of the COSMO-CLM (Consortium for Small-scale Modelling, climate version) mesoscale model, as well as using observed data. The analysis showed that the set of wind speed extremes obtained from observations is a mixture of two different subsets each neatly described by the Weibull distribution. Using special metaphoric terminology, they are labelled as “Black Swans” and “Dragons”. The “Dragons” are responsible for strongest extremes. It has been shown that both reanalysis and GCM (general circulation model) data have no “Dragons”. This means that such models underestimate wind speed maxima, and the important circulation process generating the anomalies is not simulated. The COSMO-CLM data have both “Black Swans” and “Dragons”. This evidence provides a clue that an atmospheric model with a detailed spatial resolution (we used in this work the data from domain with 13.2 km spatial resolution) does reproduce the special mechanism responsible for the generation of the largest wind speed extremes. However, a more thorough analysis shows that the differences in the parameters of the cumulative distribution functions are still significant. The ratio between the modelled Dragons and Black Swans can reach up to only 10%. It is much less than 30%, which was the level established for observations.展开更多
Bulk density is an indicator of soil compaction subject to anthropogenic impact,essential to the interpretation of any nutrient budgets,especially to perform carbon inventories.It is so expensive to measure bulk densi...Bulk density is an indicator of soil compaction subject to anthropogenic impact,essential to the interpretation of any nutrient budgets,especially to perform carbon inventories.It is so expensive to measure bulk density in arctic/sub-arctic and there are relatively very few field measurements are available.Therefore,to establish a bulk density and SOC empirical relationship in Canada’s arctic and sub-arctic ecosystems,compiled all the bulk density and SOC measurements that are available in Northern Canada.In addition an attempt has been made for bulk density and SOC field measurement in Yellowknife and Lupin,to develop an empirical relationship for Canada’s arctic and sub-arctic.Relationships between bulk density(BD)and soil organic carbon(SOC)for mineral soil and organic soils(0–100 cm depth)were described by exponential functions.The best fit model,predictive bulk density(BDp),for mineral soil,(BDp=0.701+0.952 exp(0.29 SOC),n=702,R2=0.99);for organic soil(BDp=0.074+2.632 exp(0.076 SOC),n=674,R2=0.93).Different soil horizons have different bulk densities and may require different predictive equations,therefore,developed predictive best fit exponential equation for both mineral and organic soils together(BDp=0.071+1.322 exp(0.071 SOC),n=1376,R2=0.984),where X is a dummy variable with a value of 0 for surface peat(0–25 cm depth)and 1 for subsurface peat(25–175 cm).We recommend using the soil organic carbon density approach to estimate BD from SOC because it allows BD to be predicted without significant bias.展开更多
Canada’s Arctic and sub-arctic consist 46%of Canada’s landmass and contain 45%of the total soil organic carbon(SOC).Pronounced climate warming and increasing human disturbances could induce the release of this SOC t...Canada’s Arctic and sub-arctic consist 46%of Canada’s landmass and contain 45%of the total soil organic carbon(SOC).Pronounced climate warming and increasing human disturbances could induce the release of this SOC to the atmosphere as greenhouse gases.Canada is committed to estimating and reporting the greenhouse gases emissions and removals induced by land use change in the Arctic and sub-arctic.To assess the uncertainty of the estimate,we compiled a site-measured SOC database for Canada’s north,and used it to compare with a polygon database,that will be used for estimating SOC for the UNFCCC reporting.In 10 polygons where 3 or more measured sites were well located in each polygon,the site-averaged SOC content agreed with the polygon data within±33%for the top 30 cm and within±50%for the top 1 m soil.If we directly compared the SOC of the 382 measured sites with the polygon mean SOC,there was poor agreement:The relative error was less than 50%at 40%of the sites,and less than 100%at 68%of the sites.The relative errors were more than 400%at 10%of the sites.These comparisons indicate that the polygon database is too coarse to represent the SOC conditions for individual sites.The difference is close to the uncertainty range for reporting.The spatial database could be improved by relating site and polygon SOC data with more easily observable surface features that can be identified and derived from remote sensing imagery.展开更多
An Arctic Ocean eddy in sub-surface layer is analyzed in this paper by use of temperature, salinity and current profiles data obtained at an ice camp in the Canada Basin during the second Chinese Arctic Expedition in ...An Arctic Ocean eddy in sub-surface layer is analyzed in this paper by use of temperature, salinity and current profiles data obtained at an ice camp in the Canada Basin during the second Chinese Arctic Expedition in summer of 2003. In the vertical temperature section, the eddy shows itself as an isolated cold water block at depth of 60 m with a minimum temperature of - 1.5℃, about 0.5℃ colder than the ambient water. Isopycnals in the eddy form a pattern of convex, which indicates the eddy is anticyclonic. Although maximum velocity near 0.4 m s^-1 occurs in the current records observed synchronously, the current pattern is far away from a typical eddy. By further analysis, inertial frequency osci/lations with amplitudes comparable with the eddy velocity are found in the sub-surface layer currents. After filter the inertial current and mean current, an axisymmetric current pattern of an eddy with maximum velocity radius of 5 km is obtained. The analysis of the T-S characteristics of the eddy core water and its ambient waters supports the conclusion that the eddy was formed on the Chukchi Shelf and migrated northeastward into the northern Canada Basin.展开更多
Plants typically experience great losses from their reproductive potential represented by ovule production to the post-dispersal crop of viable seed.We examined seed density and viability in a founder population of mo...Plants typically experience great losses from their reproductive potential represented by ovule production to the post-dispersal crop of viable seed.We examined seed density and viability in a founder population of mountain birch(Betula pubescens ssp.tortuosa),aiming to quantify losses at different stages and examine potential selection forces on the reproduction success of the founder generation of an isolated population.At the time of the study(2017-2020),the population had recently reached reproductive maturity,following its colonization around 1990 through long-distance dispersal onto an early successional outwash plain in southeast Iceland.Seed densities were high,but 89% of apparently intact seeds did not contain an embryo,despite being visually indistinguishable from filled seeds.Externally evident losses amounted to about 45% of the total seed crop and were mostly due to predation by the gall midge Semudobia betulae.When all losses were accounted for,2.7% of the seed crop remained viable and germinated.Pollen limitation may partially explain the high incidence of empty seeds.Excessive flower production is compatible with the predator satiation hypothesis but cannot explain pre-dispersal losses.Another adaptation to predation,masting,appears poorly developed in Iceland.Our results suggest the presence of constraints on the reproduction potential of the new island population,that are more limiting than in neighbouring populations,and we discuss their developmental,ecological,and environmental correlates.展开更多
文摘Wind speed extremes in the sub-Arctic realm of the North-East Pacific region were investigated through extreme value analysis of wind speed obtained from wind simulations of the COSMO-CLM (Consortium for Small-scale Modelling, climate version) mesoscale model, as well as using observed data. The analysis showed that the set of wind speed extremes obtained from observations is a mixture of two different subsets each neatly described by the Weibull distribution. Using special metaphoric terminology, they are labelled as “Black Swans” and “Dragons”. The “Dragons” are responsible for strongest extremes. It has been shown that both reanalysis and GCM (general circulation model) data have no “Dragons”. This means that such models underestimate wind speed maxima, and the important circulation process generating the anomalies is not simulated. The COSMO-CLM data have both “Black Swans” and “Dragons”. This evidence provides a clue that an atmospheric model with a detailed spatial resolution (we used in this work the data from domain with 13.2 km spatial resolution) does reproduce the special mechanism responsible for the generation of the largest wind speed extremes. However, a more thorough analysis shows that the differences in the parameters of the cumulative distribution functions are still significant. The ratio between the modelled Dragons and Black Swans can reach up to only 10%. It is much less than 30%, which was the level established for observations.
文摘Bulk density is an indicator of soil compaction subject to anthropogenic impact,essential to the interpretation of any nutrient budgets,especially to perform carbon inventories.It is so expensive to measure bulk density in arctic/sub-arctic and there are relatively very few field measurements are available.Therefore,to establish a bulk density and SOC empirical relationship in Canada’s arctic and sub-arctic ecosystems,compiled all the bulk density and SOC measurements that are available in Northern Canada.In addition an attempt has been made for bulk density and SOC field measurement in Yellowknife and Lupin,to develop an empirical relationship for Canada’s arctic and sub-arctic.Relationships between bulk density(BD)and soil organic carbon(SOC)for mineral soil and organic soils(0–100 cm depth)were described by exponential functions.The best fit model,predictive bulk density(BDp),for mineral soil,(BDp=0.701+0.952 exp(0.29 SOC),n=702,R2=0.99);for organic soil(BDp=0.074+2.632 exp(0.076 SOC),n=674,R2=0.93).Different soil horizons have different bulk densities and may require different predictive equations,therefore,developed predictive best fit exponential equation for both mineral and organic soils together(BDp=0.071+1.322 exp(0.071 SOC),n=1376,R2=0.984),where X is a dummy variable with a value of 0 for surface peat(0–25 cm depth)and 1 for subsurface peat(25–175 cm).We recommend using the soil organic carbon density approach to estimate BD from SOC because it allows BD to be predicted without significant bias.
基金This study is supported by a joint project between Environment Canada and Natural Resources Canada for estimation of greenhouse gases emissions and removals from land use changes over Canada’s Arctic and sub-arctic,and it is also supported by the climate change program in Natural Resources Canada.
文摘Canada’s Arctic and sub-arctic consist 46%of Canada’s landmass and contain 45%of the total soil organic carbon(SOC).Pronounced climate warming and increasing human disturbances could induce the release of this SOC to the atmosphere as greenhouse gases.Canada is committed to estimating and reporting the greenhouse gases emissions and removals induced by land use change in the Arctic and sub-arctic.To assess the uncertainty of the estimate,we compiled a site-measured SOC database for Canada’s north,and used it to compare with a polygon database,that will be used for estimating SOC for the UNFCCC reporting.In 10 polygons where 3 or more measured sites were well located in each polygon,the site-averaged SOC content agreed with the polygon data within±33%for the top 30 cm and within±50%for the top 1 m soil.If we directly compared the SOC of the 382 measured sites with the polygon mean SOC,there was poor agreement:The relative error was less than 50%at 40%of the sites,and less than 100%at 68%of the sites.The relative errors were more than 400%at 10%of the sites.These comparisons indicate that the polygon database is too coarse to represent the SOC conditions for individual sites.The difference is close to the uncertainty range for reporting.The spatial database could be improved by relating site and polygon SOC data with more easily observable surface features that can be identified and derived from remote sensing imagery.
基金the National Natural Science Foundation of China through Grants 40631006 and 40306005
文摘An Arctic Ocean eddy in sub-surface layer is analyzed in this paper by use of temperature, salinity and current profiles data obtained at an ice camp in the Canada Basin during the second Chinese Arctic Expedition in summer of 2003. In the vertical temperature section, the eddy shows itself as an isolated cold water block at depth of 60 m with a minimum temperature of - 1.5℃, about 0.5℃ colder than the ambient water. Isopycnals in the eddy form a pattern of convex, which indicates the eddy is anticyclonic. Although maximum velocity near 0.4 m s^-1 occurs in the current records observed synchronously, the current pattern is far away from a typical eddy. By further analysis, inertial frequency osci/lations with amplitudes comparable with the eddy velocity are found in the sub-surface layer currents. After filter the inertial current and mean current, an axisymmetric current pattern of an eddy with maximum velocity radius of 5 km is obtained. The analysis of the T-S characteristics of the eddy core water and its ambient waters supports the conclusion that the eddy was formed on the Chukchi Shelf and migrated northeastward into the northern Canada Basin.
基金supported by the Icelandic Research Fund(173688).
文摘Plants typically experience great losses from their reproductive potential represented by ovule production to the post-dispersal crop of viable seed.We examined seed density and viability in a founder population of mountain birch(Betula pubescens ssp.tortuosa),aiming to quantify losses at different stages and examine potential selection forces on the reproduction success of the founder generation of an isolated population.At the time of the study(2017-2020),the population had recently reached reproductive maturity,following its colonization around 1990 through long-distance dispersal onto an early successional outwash plain in southeast Iceland.Seed densities were high,but 89% of apparently intact seeds did not contain an embryo,despite being visually indistinguishable from filled seeds.Externally evident losses amounted to about 45% of the total seed crop and were mostly due to predation by the gall midge Semudobia betulae.When all losses were accounted for,2.7% of the seed crop remained viable and germinated.Pollen limitation may partially explain the high incidence of empty seeds.Excessive flower production is compatible with the predator satiation hypothesis but cannot explain pre-dispersal losses.Another adaptation to predation,masting,appears poorly developed in Iceland.Our results suggest the presence of constraints on the reproduction potential of the new island population,that are more limiting than in neighbouring populations,and we discuss their developmental,ecological,and environmental correlates.
