GC13A-0928
Do Extreme Climatic Events Drive Ecosystem Water Flux Under Elevated CO2 in a Temperate Forest?
In 2007, much of the Southeastern US experienced a combination of extreme weather events that visibly damaged plant communities across entire landscapes; including a Liquidambar styraciflua (sweetgum) plantation in eastern Tennessee concurrently exposed to elevated CO2 treatments. At the Oak Ridge National Lab's FACE facility there was a late spring freeze event (-6.5 °C) as leaves were emerging, followed by a record summer drought with forest understory temperatures reaching 38.5 °C. Trees exposed to elevated CO2 often have lower rates of evapotranspiration (ET) which can reduce total site water use, thereby buffering trees against droughty conditions. Sap flux density was monitored in 16 trees using Granier- style sensors to access the potential of a CO2 treatment-mitigated buffering of perceived plant water stress, and thereby productivity. While up to 60% of young expanding foliage was visibly damaged across treatments following the freeze event, it represented a minor component of subsequent canopy leaf area with no distinguishable impact on sap flux. Trees exposed to elevated CO2 initially had lower ET than ambient trees, but differences diminished as soil water potential dropped below -0.5 MPa reflecting the increasing water limitations. Sap flux density declined more readily in ambient CO2 trees during droughty periods, but subsequently recovered following significant rain events. This research suggests that plant response to seasonal dynamics in water availability may be modulated (less responsive) under a projected future CO2 scenario.
GC13A-0929
The Effect of CO2 Stabilization on Uptake Rates in Land and Ocean Sinks as a Function of Ocean Circulation, Vegetation Type, and CO2 Fertilization
In order to mitigate effects of climate change, governing entities need to limit carbon dioxide (CO2) in the atmosphere to a concentration yet to be determined. To assist policymakers, this experiment tested selected sensitivities of the land and ocean sinks to a proposed CO2 stabilization scenario of 600 parts per million by 2100. Sensitivities evaluated were the effect of CO2 fertilization on vegetation, the effect of long-lived forests vs. short-lived steppes, and the effect of various ocean circulation rates. All simulations were done with Tethys, a four-box earth-systems model consisting of a vegetation-soil reservoir, ocean, atmosphere, and emissions source. Results are generated through a series of equations written in IDL code, parameterized to simulate key processes in the climate-carbon cycle. Results generated in response to ocean and land sink behavior included peak allowable emissions, CO2 uptake rates in a reservoir, and the maximum amount of allowable emissions to maintain concentrations at 600 ppm. Tethys predicted that the rate of carbon uptake in the oceans will decrease with an increase in circulation time, and that the vegetation sink will cease to exist soon after atmospheric CO2 is stabilized. Simulations suggest that grasslands will absorb more CO2 than forests, a result that indicates a flaw in the model. The carbon cycle sensitivities tested in this experiment determine how much humans can emit and how quickly emissions need to be reduced to meet stabilization goals. Future sink behavior should be incorporated into any plan that seeks to stabilize atmospheric CO2.
GC13A-0930
Extreme drought and temperature conditions lead to variable response in Arctic tundra carbon flux
Recent trends in the carbon flux of Alaskan Arctic tundra ecosystems show significant spatial variability across the Pan Arctic, from sink activity (wet sites indicative of the coastal climates) to neutral or slightly source activity (moist sites indicative of inland climates) over many years. The conditions during summer 2007 were significantly warmer, drier, and had increased available light than previous years. Both sites exhibited average temperatures >40% higher, total precipitation >60% lower, and available light >10% higher than average. At the cooler, coastal, wet sedge tundra site (Barrow), the ratio of sensible to latent heat flux increased 25%, and at the warmer, moist tussock tundra site (Atqasuk), nearly doubled. Although the microclimatological trends were similar between the sites, the carbon flux response was disparate. Increased temperature and decreased precipitation resulted in greater efflux from Atqasuk; however, the increased temperature and, surprisingly, decreased precipitation, resulted in increased photosynthetic activity at the Barrow site. The extreme conditions displayed in summer 2007 have also helped to parameterize the factors influencing carbon flux across the arctic landscape and will therefore increase the ability to understand the potential effects of future climate change.
GC13A-0931
Environmental Impacts of C02 Storage
\begin{document} The electric power industry is investigating the feasibility of storing carbon dioxide (CO2) for the long term in deep geologic formations suited to that purpose. Much of the technology needed for engineered CO2 storage has been developed by those engaged in oil and gas exploration and production, but the quantity of CO2 that will be involved under a nationwide program of CO2 capture and storage from power plants dwarfs the current experience base with enhanced oil recovery. Therefore, it is important to consider the potential environmental impacts of such an undertaking. These impacts may include releases to air from the storage site or transportation system and to groundwater from the injection formation. Impacts can also be secondary in nature, such as induced seismicity (earthquakes). Research will focus on these potential environmental impacts individually, indicating for each what is known about the impact, what data gaps exist, and what research should be conducted to eliminate/minimize the gaps. The focus of research will be on environmental impacts in the event the injected CO2 escapes from its transport or storage containment or causes indirect effects such as earth movement and on the potential risks of such behaviors and consequent impacts. Other studies will focus on engineering methods, such as modeling and monitoring, to mitigate these potential occurrences. \end{document} http://www.epri.com
GC13A-0932
Holocene and Late Glacial Climate Change in Central Japan
In an attempt to reconstruct the climate for the last 40 ka in central Japan, sediment cores from Lake Aoki, located close to the northern Japanese Alps, and Lake Yamanaka, at the northern foot of Mt. Fuji, were investigated for grain-size, diatoms, and total organic carbon (TOC) and total nitrogen (TN) contents. TOC flux and diatom abundance are closely positively correlated in both short-and long-term fluctuations. Changes in surface water temperature and paleohydrology appear to be the main factor affecting the variability in the proxy records. An abrupt decrease in sand and clay contents and increase in TOC flux and diatom abundance at 13 ka cal BP is interpreted as the last Glacial Holocene boundary. During the Glacial Period, more cooling events centered ca. 16, 28, 34, and 39 ka cal BP can be correlated with the Henrich events H1, H2, H3 and H4, respectively. The Last Glacial Maximum reaches its peak ca. 22 ka cal BP. Beginning with a rapid warming, the Holocene climate history is characterized by an alternating sequence of seven warm and seven cool phases with abrupt transition and lengths lasting from hundreds to thousands of years. Climatic events such as the Little Ice Age (LIA), the Younger and Older Dryas, the Medieval Warm Period, and the Holocene Optimum are evident, and some other warm and cool events not previously well recorded are also apparent. Generally, the Holocene was warmer than the present time but cool periods even colder than the LIA are also observed. The magnitude of climate change observed after the LIA was commonplace in the Holocene.
GC13A-0933
Interannual Variability of Primary Production and Fishery in Response to Climate Changes in the Bering Sea
The climate trends of reducing sea ice cover and rising temperature have profound impacts on the lower tropic level production and fishery production. The lower trophic level production from 1970 to 2005 was simulated using a vertically 1-D coupled ice-ocean ecosystem model (Jin et al., 2007) that includes 10 compartments: three phytoplankton (pelagic diatom, flagellates and ice algae), three zooplankton (copepods, large zooplankton, and microzooplankton), three nutrients (nitrate+nitrite, ammonium, silicon) and detritus. By using a turbulence closure model (Mellor, 2001), tidal mixing and its interactions with wind stirring, and thermal stratification were realistically reproduced. The 1-D model was applied to the mooring site M2 in the southeastern Bering Sea. The water depth H=74m. The model is forced by NCEP reanalysis data and sea ice concentration data from Hadley Center (monthly) before 1978 and SSM/I (daily) after 1997. Surface boundary includes wind stress, heat and salt flux. Model results are validated favorably with observations: 1) temperature, salinity, fluorometer data at 12m, 24m and 44m at NOAA/PMEL mooring from 1995-2005; 2) daily SeaWiFS chl a data (1997-2005). While the quantity of variability of the primary production did not show an increase/decrease trend in the past three decade, there exists a shift of dominant phytoplankton species coincident of the Pacific Decadal Oscillation (PDO) index. The model primary production were dominant by ice algae before the 1976/77 regime shift, and by open water species of diatom and flagellates thereafter with only occasional ice algal blooms. Fish catches in the eastern Bering Sea showed mixed reponse to the climate changes. Among the 12 dominant economic fish species, only Walleye pollock and Yellowfin sole showed significant correlations with the PDO index in certain regions. http://people.iarc.uaf.edu/~mbj/
GC13A-0934
Global Warming, Climate Change and Glacier Retreat of Nepal Himalayas
Global average air temperature near the earth surface rose 0.74¡¾0.18¨¬C during the twentieth century. The Intergovernmental Panel on Climate Change (IPCC) concludes that observed increased globally averaged temperatures since mid-twentieth century is very likely due to the observed increment in anthropogenic greenhouse gas concentrations, which leads to warming of the surface and lower atmosphere by increasing the greenhouse effect. Climate models referred by IPCC project that global surface temperature are likely to be increase by 1.1 to 6.4¨¬C between 1990 and 2100. An increase in global temperature is expected to cause other changes including glacier retreat, sea level rise, increase intensity of extreme weather events and change in the pattern of precipitation, etc. The Nepal Himalaya revealed 3,252 glaciers and 2,323 lakes, which are 3,500 m above the sea level. They cover an area of 5,323 km2 with an estimated ice reserve of 481 km3. The average temperature in Nepal is rising by 0.5¨¬C per decade, and because of this reason, big glacial lakes in the country are at high risk of flooding from glacial lake bursts, which would have an adverse effect, such as huge loss of life and property. Nepal is facing a disturbance in mountain climate, flash floods, cloudbursts, erratic weather patterns and so on. The death of number of people due to floods and landslides is increasing annually. It is reported that more than 164 people already died because of floods and landslides during the current year, 2007 rainy season. Nepal does emit negligible greenhouse gases compare to developed and industrialized countries, however, country and people are facing the consequences of actions of other developed and industrialized countries. Study shows the¡¡disasters in current years and possible hazards in future due to the probable causes of global warming and recommends some suggestions for controlling of green house gases emission.
GC13A-0935
A Closer View of Glacial Earthquakes Around Jakobshavn Glacier, Greenland, Using a Portable Seismic Array
Project SMOGIS (Seismic Monitoring of Greenland's Ice Sheet) the deployment of an array of portable seismic sensors around Swiss Camp (69.5N, 49.5W), some 50 km North of Jakobshavn glacier's ice stream (Western Greenland), has so far resulted in the possibly unprecedented detection of long lasting (up to 40 min. long) seismic "rumblings" which can be described as sustained seismic wave radiation episodes. We detected at least 80 of these in the 180 days of recording (May-August, 2006/2007). We also detected a number of sharp and short (15-20 s. long) distinguishable seismic events with source characteristics consistent with double couple mechanisms that occur during every rumbling and are clearly associated with them. These bona-fide earthquakes show strong P and S-wave radiation with amplitudes normally greater than the background rumbling, and are located around the margins of the ice stream that feeds Jakobshavn, some 50km south of the SMOGIS array. An important characteristic of the rumblings is that they are all very similar, despite their different durations, suggesting a fundamental similarity of process, a possibility that we are currently examining. A few rumblings were also detected by the global seismic network (GSN) and classified as glacial earthquakes, but the closer inspection allowed by SMOGIS reveals that they are more complex and intriguing than previously reported. Synthetic seismograms indicate that the focal mechanism of the double couple events is consistent with ENE oriented, nearly vertical fracture planes along which strike-slip motion with 20% vertical component takes place between the wedged ice and the graben's wall rock. Best fitting seismograms occur for a focal depth of ~2km below the surface of the ice stream. Since their occurrence seems controlled by the warm season, a long-term study of these rumblings should provide plausible upper limit for the ice volumes that outlet glaciers are able to drive into the ocean as the Arctic continuous to warm due to increasing global emissions of greenhouse gases into the atmosphere.
GC13A-0936
Glacier fluctuations during the last 400 years at Mount San Lorenzo and Santa Ines Island, southern Chile
We examine the local glacier fluctuations for the last 400 years in two mountain areas of the western coast of southernmost South America, Mount San Lorenzo and Santa Ines Island, using dendroglaciologic, geomorphologic and historical evidence. Mount San Lorenzo moraines span between 1636 and 1927 with periods of more frequent occurrence of glacial advances for the years 1670, 1770, 1870 and 1910. Santa Ines glacial advances are less numerous than in Mount San Lorenzo with well defined, clearly separated frontal moraines. The moraines were colonized by Nothofagus betuloides and Nothofagus antarctica two species with clear and well-preserved tree rings and the total age of the sampled trees was more precisely estimated. Dated moraines cover the last 300 years with evidence for advances during late 1600s, around 1800, 1860, 1910, 1930 and 1960. Further work is needed in dendroglaciological dating, geomorphologic surveying, and better understanding of local glacial dynamics for several glaciers to obtain a regional history of the glacier fluctuations of the southern Andes.
GC13A-0937
Global Cloud Detection and Distribution with Night Time using Satellite Infrared Data
Knowledge of the current climate system is necessary to clearly estimate large-scale global warming and abnormal weather in the future. Net radiation is one of the main factors that influence a climate system. The earth, which is covered by cloud of dozens of surface giving it a high albedo, reflects a large part of solar radiation. In addition, during nights, when the earth's radiation increases, the earth acts as a radiator. There is no doubt that clouds are closely related to the radiation balance. Satellite data analysis is the most useful method to understand cloud climatology. The targets are to establish an algorithm to detect clouds for night term of the earth, and to get to know more about global cloud distribution with night term. Brightness temperature difference of split window channels is used in this method. We decided three thresholds which have some slopes are used in the case of over land, open sea, and snow or ice surface including sea ice, respectively. We examined on some sensors which has difference response function in itself plat home, GLI/ADEOS2, AVHRR/NOAA, MODIS/Terra and Aqua.
GC13A-0938
Variations in the Relationship Between Precipitation and Tree Growth in the North-Central Rocky Mountains Identified Using a Tree-Ring Network
Much of the western United States is in the midst of a multi-year drought that has placed a renewed sense of urgency on water availability issues. The characterization of variability over relevant space and time scales has emerged as one of the top needs concerning the hydrological cycle, but understanding hydroclimatic variability at decadal and longer time scales has been limited by instrumental data that are both spatially and temporally inadequate. The reconstruction of moisture variables from tree-rings has been recognized as an important source of information on long-term water supply variability. Moisture variables of interest may include annual precipitation, snowpack, summer precipitation, and streamflow. Trees in closely co-located sites can vary widely in the signal they reflect, particularly in a region with the complex topography and hydroclimatic variability that is seen in the north-central Rocky Mountains. In this study, climatic and geospatial information was combined with tree-ring chronologies in order to better-understand factors determining variations in the response of tree growth to a particular precipitation signal. Resulting spatial variability in moisture seasonality and growth response provide insight into the region's moisture patterns and better characterization of the region's hydroclimatic variability.
GC13A-0939
Project Of Investigation About Growth Of Afforestation Mangrove In Thailand
At the mangrove which was played back artificially by intended afforestation it designates that related characteristic of growth circumstance and growth environment of the mangrove plant which is grown is evaluated as purpose of this study.@ Revival of the mangrove in Thailand with afforestation makes the ecosystem revive which consists simultaneously with the mangrove, makes the fishing industry profit at neighborhood possible, makes the life of the people of the locale rich. In addition, the mangrove carries out the role of the anti wave forest, the case of the Sumatra open sea earthquake makes the damage decrease by the tidal wave. The people of the locale re-have recognized concerning the inevitability of the mangrove. Difference has occurred in the amount of mangrove growth depending upon the growth place, the fact that these causes are investigated is something which urges the growth of the efficient mangrove at the time of future afforestation being active. In addition, also comparison of growth circumstance of the mangrove due to natural growth and the mangrove due to afforestation becomes the important research resource. Concretely, it measures growth circumstance (height of tree and diameter etc.) and also, growth environment (the amount of solar radiation, salinity density in substrate and tidal change etc.) and evaluate both correlations. As for evaluation of growth environment of the afforestation mangrove we should evaluate with central value. Because of that, there is a necessity which executes amount of growth measurement with statistical technique. Therefore, with the amount of growth measurement with lumbering, it is unsuitable to the measurement on this study. Regarding this subject of study, growth investigation of the group of trees is executed making use of non destructive physical amount (height of tree and diameter etc.) measurement. It measures at several dozen threes in plural afforestation area, evaluates the growth environment of each afforestation mangrove and the related characteristic of growth circumstance.
GC13A-0940
Comparison of Topographic Effects between the Enhanced Vegetation Index (EVI) and Normalized Difference Vegetation Index (NDVI)
Vegetation indices play an important role in monitoring variations in vegetation. The Enhanced Vegetation Index (EVI) proposed by the MODIS Land Discipline Group and the Normalized Difference Vegetation Index (NDVI) are both global-based vegetation indices aimed at providing consistent spatial and temporal information regarding global vegetation. However, many environmental factors such as atmospheric conditions and soil background may produce errors in these indices. The topographic effect is another very important factor, especially when the indices are used in areas of rough terrain. In this paper, we analyzed differences in the topographic effect between the EVI and the NDVI based on a non-Lambertian model and using two airborne-based images with a spatial resolution of 1.5m acquired from a mountainous area covered by a homogeneous Japanese cypress plantation. The results indicate that the soil adjustment factor "L" in the EVI makes it more sensitive to topographic conditions than is the NDVI. Based on these results, we strongly recommend that the topographic effect be removed from the EVI—as well as from other vegetation indices that similarly include a term without a band ratio format (e.g., the PVI and SAVI)—when these indices are used in conjunction with a high spatial resolution image of an area of rough terrain, where the topographic effect on the vegetarian indices having only a band ratio format (e.g., the NDVI) can usually be ignored.
GC13A-0941
Relationship Between Land Subsidence and the Earth Surface Environment at Kujukuri Plain in Chiba Prefecture, Japan
This study investigated a long-term spatio-temporal change of land subsidence at Chiba prefecture, Japan, and compared with temporal change of the earth surface environment. Land subsidence has occurred across the wide area of Chiba Prefecture. It is concerned that continuous land subsidence may increase possibilities of environmental changes such as stream regime, increase of floods, and saltwater intrusion. Precise prediction and appropriate management of the environmental changes in the future require better understandings of temporal change and spatial distribution of land subsidence in detail and evaluating of their impact to the natural environment. Previous studies have mainly dealt with the subsidence data during recent 40 years. Thus firstly, we investigated older data of first order leveling survey carried out by Geographical Survey Institute in Japan and integrated those data into recent results. The integrated data revealed the temporal change of land subsidence for past 100 years; for example, subsidence has generally started from the early 1960s in the study area. Then, spatial distribution of land subsidence was examined by data processing with a GIS software. Secondly, we compared the settlement values with natural and artificial settings including altitude, slope angle, geologic age, geomorphologic classification, and land use to examine what kind of locations are susceptible to subsidence. As a result, we found that valley bottom or lowland, i.e., locations with low-altitude, low-slope angle and new geologic age, are susceptible to subsidence. Finally, temporal change of land cover was revealed using old topographic maps. Then, we compared the temporal change of land cover with ground level and discussed their relationships.
GC13A-0942
Geothermics of Climate Change: Linking Ground and Air Temperature Change Through Repeat Temperature Measurements in Boreholes From Northwest Utah
Temperature-depth profiles measured in boreholes contain important information about the Earth's changing surface temperature and provide a direct method for reconstructing surface temperature variations over the past several centuries. Differences between temperature-depth logs, on annual to decadal timescales, provide an important test of borehole thermometry. Twelve temperature-depth logs at the northwestern Utah Emigrant Pass Observatory (EPO) borehole, GC-1, seven at borehole SI-1 and five at borehole DM-1, were acquired between the years 1978 and 2007. Differences in temperature logs extend to about 100 m. Below 100 m, differences between temperature logs are effectively zero. SAT data from the meteorological station at EPO and nearby Historical Climatology Network stations are used as a forcing function at the Earth's surface and diffused into the subsurface. These transients reproduce observed subsurface temperature variations reasonably well at each borehole. Comparisons between repeated temperature-depth profiles and diffused SAT transients over the same time period offer strong support for using GST histories to complement SAT data and multi-proxy reconstructions in climate change studies.
GC13A-0943
Facilities Enhancement for IPY at Barrow
In connection with the International Polar Year, research facilities at Barrow have been markedly enhanced. On June 1st, Sen. Ted Stevens cut the ribbon at the Grand Opening of the Barrow Arctic Research Center (BARC). The BARC currently covers 18,000 sq. ft, with future phases anticipated, including 8 research labs, a necropsy lab for animal studies, freezers for biological samples, a state-of-the-art-data system, a planned Internet II connection, meeting spaces, and offices. There is a platform on the roof of the facility for instrumentation, and a communications tower to provide WIFI connections to remote instrumentation located on the adjacent Barrow Environmental Observatory (BEO). The BEO, which consists of 11 square miles of tundra and coastline set aside for environmental and ecological research, has also seen recent enhancements. A power line and a hard- surfaced trail now provide easy access to the interior of the BEO. Users of the BEO (and others) also have access to many different data sets continuously collected at the NOAA Global Monitoring Division Barrow Station and the DOE ARM (Atmospheric Radiation Measurement) Climate Research Facility (see http://www.esrl.noaa.gov/gmd/obop/brw.html and http://www.arm.gov/sites/nsa.stm respectively) also adjacent to the BEO. The National Weather Service Barrow Station also provides data of interest. Researchers submitting proposals to the National Science Foundation can include a request for the use of BARC and BEO facilities in their proposals. ARM facilities, recently augmented, can also be made available, but through arrangements made directly with ARM (BDZak@sandia.gov; 505-845-8631 or MDIvey@sandia.gov; 505-284-9092). BARC, BEO and ARM facilities are available to other agency and international users as well. For more information, see http://www.arcticscience.org, or contact Glenn Sheehan (907-852-4881, basc@arcticscience.org). The BEO consists of land owned by Ukpeagvik Inupiat Corporation, which is owned by the native people of Barrow. The BEO is administered by the Barrow Arctic Science Consortium (BASC) under a Cooperative Agreement with the National Science Foundation. BASC is a non-profit entity set up to serve the logistical needs of scientists doing research on the North Slope of Alaska. http://www.arcticscience.org
GC13A-0944
A Megamodel-Classifier in Support of a Sampling Strategy Using Landsat Data to Estimate Deforestation in the Brazilian Amazon
The rainforest of the Brazilian Amazon is subject to high rates of deforestation. Estimates of deforestation are needed for management decisions and policy support. A strategy that provides timely estimates of basin-wide forest cover change would be beneficial to policy makers and land managers alike and provide useful information more quickly than current, large-scale efforts. This study employed a megamodel based on a decision tree algorithm using Landsat data from 2000 and 2005 in an automated, sampling block pair approach to estimate deforestation for the Brazilian Amazon. The megamodel, unlike locally derived models, is generic and can systematically characterize a large number of sampling block pairs automatically over large geographical regions. We trained the megamodel on a subset of pixels taken from sampling block pairs that were interpreter-classified into deforested area and unchanged forest. We assessed the megamodel in a three stage procedure: (1) We tested the model on the sampling block pairs that we derived the training from, (2) we used a bootstrapping approach to evaluate the classification accuracy, and (3) we applied the megamodel to new sampling block pairs and evaluated the classification accuracy against PRODES digital deforestation estimates. The first test of the megamodel resulted in 96% overall classification accuracy suggesting that the megamodel is a robust classifier capable of producing accurate estimations of forest cover change for the Brazilian Amazon. Misclassification occurred (A) because of spectral classes that were underrepresented in the training and (B) because of spectral classes that the interpreter labeled arbitrarily from one to another sampling block pair in the training. The Brazilian Amazon provides a test bed for the megamodel classifier because deforestation and unchanged forest thematic classes are spectrally homogenous across the forested area of the basin.
GC13A-0945
Influence of Spatial Components of Uncertainty on the Prediction of Carbon Disturbed by Deforestation in the Brazilian Amazon
The prediction of carbon emissions from tropical deforestation is critical to anticipate the magnitude and consequences of global warming. This prediction involves several sources of uncertainty that need to be identified and measured. In this work, we evaluate how spatial components of uncertainty influence the prediction of carbon disturbed by deforestation in the Brazilian Amazon forest. The specific components of uncertainty are the accuracy on the prediction of quantity and location of deforestation and the variability and uncertainty in the spatial distribution of carbon. Five maps representing the spatial distribution of carbon in the study area are used to calculate the absolute minimum, maximum and mean carbon disturbed under different simulated intensities of deforestation. These results are also compared with the estimation of carbon disturbed by deforestation in areas where actual deforestation occurred between 2000 and 2005. Results indicate that the most influential component of uncertainty is the accuracy on the prediction of quantity of deforestation followed by the uncertainty on the spatial distribution of carbon. The effect of the accuracy on the prediction of location however is trivial compared to the other two components. In order to reduce uncertainty in the prediction of carbon disturbed by deforestation in the Brazilian Amazon, efforts should be focused on improving both the prediction of the total area that will be deforested and the representation of the spatial distribution of carbon rather than on the prediction of where deforestation will occur. This analysis constitutes a basis to set priorities on reducing uncertainty associated to the prediction of carbon emissions from tropical deforestation and may contribute to the design of forest-based mechanisms to mitigate global warming.
GC13A-0946
Field Investigations of Landscape Development in southeast Spain for use in Modeling Holocene (8,000 - 1,500 yr) Agropastoral Landuse and Landscape Interactions
Dramatic changes in land use were associated with the rise of agriculture in the mid Holocene in the Mediterranean region. Both the surface properties and the drainage networks were changed. Along with the direct modifications to surface properties (vegetation removal and change, sediment liberation and compaction) and consequent drainage alteration (terracing, canals), up and downstream responses in the watersheds communicated these changes throughout the landscape. The magnitude, rate, and feedbacks with the growing human populations are critical questions in our effort to assess human-landscape interactions. To investigate these relationships, recent field work in the Penaguila Valley in southeast Spain included landform mapping, alluvial deposit description, and sample collection emphasizing areas of active erosion, remnant land surfaces and their relation to archaeological sites. We have updated our geomorphic maps by refining the delineation of alluvial terraces, steep-walled (40m deep) drainages ("barrancos"), and hollows ("barrancos de fondo plano"). Hollows are curved, elongate, flat-bottomed gullies with steep walls (2-30m tall) and extend headward from the main barrancos. This work enables more accurate terrace correlations necessary for both landscape evolution modeling and interpretation of the development history of the basin. Alluvial terraces are crucial to this research because they record periods of past stable topography. In the Penaguila, sites dating back to late Mesolithic and early Neolithic (around 6600 BP) and subsequent periods (Chalcolithic and Bronze Age) are exposed on a prominent terrace surface mapped as Terrace A. This broad low relief surface is scarred by deep barrancos and hollow formation that expose bedrock marls and overlying alluvial deposits. Stratigraphic profiles and texture analyses of Terrace A deposits reveal overland flow facies and channel networks in reworked and CaCO3-encrusted marls, and several organic-rich paleosols. Small remnant surfaces mapped as Terrace Z (below Terrace A) were observed within the main barrancos and indicate a later, brief accumulation period with subsequent incision to the modern channel. Holocene landscape development in the Penaguila appears to have progressed from a period of stability to slope denudation with aggradation (stream infilling) followed by rapid incision which initiated sometime near the time of occupation. This change from a low relief alluvial surface to one cut by narrow channels may have been an important shift for local populations. Their response to that environmental modification may be associated with the horticulturalist to agricultural intensification noted in the archaeological record. Tighter chronology and better understanding of the driving processes for barranco incision and hollow formation will improve our ability to correlate the changing landscape with land use practices. Such an improved correlation leads to better understanding of human-landscape interactions.
GC13A-0947
South Dakota Regional Diversity of Air Temperature Regime: System Analysis of Empirical Data
The regional diversity of monthly temperatures were analyzed based on long-term data obtained for South Dakota (SD) from the High Plains Regional Climate Center. System hierarchical model of landscape (Krcho, 1990) was used for research tasks formulation. Initial matrixes for three tasks were compiled for the state. The first set of initial matrices of time series Xt*n, where t = number of years and n = number of meteorological stations, contains three matrixes: X(67*29), X(57*58)and X(33*94). The second set - Xt*m, where t = number of years and m = number of months in a year: X(113*12), X(110*12), and X(102*12). The third set - Xn*m, where n = number of meteorological stations and m = number of months in a year, contains two matrixes: X(29*12) and X(94*12). Factor analysis was used and the models of regional regime air temperatures have known and high (87 and 91%) representation of a variability of the initial matrix, while the models for seasonal regime have lower representation (60 and 61%). The models for distributions of average monthly temperatures have the highest representation of variability in the initial matrix (94 and 97%). Statistical analysis allowed us to differentiate between weather stations by temporal trends and spatial distribution during the time intervals 1932-1998, 1949- 2005 and 1963-1995. The most variable stations (Brookings, Camp Crook, and Highmore) were determined for the longest time interval 1932-1998. Their seasonality was described (the most variable months and correlation among months during the year); and their annual and seasonal regimes were determined and described with the use of simplified Fourier analysis. The average annual and monthly temperature distributions were presented for SD based on 29 (1932-1998) and 94 stations (1963-1995). Spatial temporal regimes of monthly air temperatures for SD on basis of analyzing existing empirical data has to be regarded as a multidimensional process with cyclic positive and negative trends as well as fuzzy regional boundaries of units with different regimes. The obtained result may have immediate application for developing a climatic monitoring network in SD and establishing a plan for regional drought research in SD to help in understanding the bigger picture of monthly and annual air temperatures regimes in SD and their connection to global and continental temperatures.
GC13A-0948
Integrated modelling and GIS: A new approach to assess desertification vulnerability and risk in Sardinia Island (Italy)
Land degradation assessment is a prior goal in decision support system for environmental protection, mainly in the Mediterranean area. Among various approaches, a model based methodology seems the most effective to monitor degradation processes and to plan mitigation actions, as it combines synergically many indicators categories of DPSIR (Driving Forces, Pressure, State, Impact, Response) framework. The presented approach is applied for desertification risk evaluation in Sardinia (Italy). Assuming desertification as the interaction among both predisposing (i.e. geographic location), triggering (i.e. extraordinary climatic events) and quickening (i.e. as human activities) factors, a new methodology was developed combining together, in the structure of an integrated model framework, a wide range of desertification indicators already developed by various projects focusing on Mediterranean area. A large multi-thematic dataset has been acquired consisting of about eighty geographic information layers. This data have been processed and re-arranged in a GIS environment in order to supply the input to several models regarding the typical degradation processes occurring in the Mediterranean area. In this study five processes were taken into account: soil erosion, soil biological degradation, loss of vegetation productivity, coastal aquifer salinization and overgrazing. The modelling procedure has been applied for two different periods according to the largest availability of data: the early nineties and the present. The outcomes from the model simulations were spatialized into separated vulnerability maps, one for each degradation process. Model results were normalized as indices varying from 0 (no degradation) to 1 (irreversible degradation); then, these degradation indices are integrated into a final one, with the same range of values, combining together different aspects of desertification, their magnitude and their development rate, giving different weights according to the importance of a single process and the quality of input data. This approach allows to highlight both spatial and temporal variability of desertification phenomenon, as well as to estimate land vulnerability as respects each single degradation process. The temporal variability is driven by both past trends and future simulations of land use and climate changes. The results have been then validated by applying the same methodology on a larger scale for an area resulting as hotspot of desertification from the first application on a smaller scale, in order to detect and verify the real situation. The risk is considered the final product between vulnerability and value of "at risk" elements. Moreover, from environmental vulnerability assessment and jointly with more strictly socio-economic aspects of land use change directions and scenarios, it will be possible to detect areas at different risk for the future, again in a GIS-oriented approach, supplying an useful tool in predisposing prevention, adaptation or mitigation countermeasures to desertification.
GC13A-0949
The Prominence of Decadal and Multidecadal Variability in North American Precipitation
Recent studies have suggested that the risk of drought over North America changes at timescales of one to several decades, and that these changes are coherent over large areas. We present a complementary perspective that measures the importance of these signals at the local scale. We use singular spectrum analysis to identify regions in North American where decadal to multidecadal (D2M) signals make up a significant fraction of the total variance in annual or seasonal precipitation. In most regions, D2M variability is not significant, as precipitation is dominated by interannual variability and secular trends. Decadal variability is significant at the regional scale in some seasons, most prominently in Minnesota and northern California during winter, and the central Rocky Mountains in autumn. Eastern Quebec is the only region where precipitation exhibits significant variance in the multidecadal band. D2M variability in these four regions is generally not coherent, and does not resemble major modes of climate variability. Decadal signals in the discharge of the Sacramento River and, to a lesser degree, the Colorado River are coherent and in phase with similar signals in regional precipitation. It is possible that D2M signals in other aspects of the climate system or amplification of weak D2M signals in precipitation by landscape response could create large changes in drought severity on decadal or multidecadal timescales. However, our results indicate that changes in precipitation cannot by themselves be the cause of significant D2M variability in drought over most parts of North America.
GC13A-0950
Abrupt changes in rainfall during the twentieth century
A sudden change in climate is brought about by complex interactions in the climate system, including interactions between land and atmosphere, that can give rise to strong positive feedback mechanisms. Paleoclimatic studies have shown that abrupt climate changes have happened in the geologic past. Studies of future climate change under global warming scenarios indicate the possibility of the sudden collapse of the thermohaline circulation, which will have major implications for the climate of Europe. However, abrupt climatic changes are not events of the geologic past or a computer-simulated future: they have occurred in recent history and have had serious consequences on society and the environment. The prolonged Sahel drought in the late 1960s and the Dust Bowl of the 1930s are examples of abrupt climatic changes of the twentieth century. Apart from these events, however, there has been no systematic survey of recent climate history to determine the prevalence of abrupt climatic changes. Given the potential cost of these abrupt changes, there is a need to investigate historical records for evidence of other sudden climatic changes in the more recent past. Here we analyze the Climate Research Unit global historical rainfall observations (covering the years 1901-2000) using wavelet analysis to detect regions that have undergone large, sudden decreases in rainfall. We show that in the twentieth century, aside from the Sahel and the US midwest, at least 30 regions in the world have experienced sudden climatic changes. These events are statistically significant at the 99 percent level, are persistent for at least ten years, and most have magnitudes of change that are 10 percent lower than the climatological normal (1901-2000 rainfall average). We also illustrate some of the potential consequences of these abrupt changes and show that these events had major impacts on social and environmental conditions. Interestingly, these regions of abrupt precipitation changes are mostly located in semi-arid and arid regions (with rainfall amounts of about 350-700 mm per year). This is consistent with climate modeling results, which include the effects of dynamic vegetation cover. These studies show that arid and semi-arid regions are more likely to have multiple equilibrium states and exhibit abrupt "regime shifts" between states. Our analysis shows the extent and magnitude of sudden decreases in rainfall across the globe during the 20th century and is an important first step for studying dynamics of and the mechanisms behind these abrupt changes.
GC13A-0951
Dust Generation From the Sahara-Sahel Region: New Insights From Helium-4 in a Red Sea Coral
Mineral dust emitted from arid and semi-arid regions of North Africa is an important component of the Earth's climate. Over the last four decades dust emissions from the Sudano-Sahel region have increased dramatically, which has been related to prolonged droughts in the region. However, in the absence of long term dust records in the extratropical region, downwind of the African sources, it is difficult to quantitatively constrain the factors responsible for the observed trends in dust activity in North Africa. Here we present a long term (>100 years) proxy record of annual dust fluxes from the Sahara-Sahel region using Helium isotopic measurements from a Red Sea coral. The coral sample was collected in 1995 from the northern Red Sea (27°43 N, 34°07 E). Our previous work has demonstrated that corals incorporate dust into their skeleton in proportion to the atmospheric column abundance and 4He is an effective tracer of the dust. We find that high 4He fluxes in the Red Sea coral occur in the 1880's, 1900's 1910's, 1920's 1940's, 1970's and early 1980's, all associated with drought events in the Sudano-Sahel region. Low 4He fluxes in the 1930's are associated with wet episodes in the Sahel, while the lowest 4He fluxes are in the 1950's, associated with the wettest decade of the 20th century. Our 4He-based proxy record of dust is correlated with instrumental records of rainfall in the Sahara-Sahel region. Thus, long-term precipitation and drought patterns in the region can be reconstructed from the 4He- based proxy record of dust in corals. We also find that in addition to rainfall, coupled ocean-atmospheric phenomenon such as the North Atlantic Oscillation and El Nino-Southern Oscillation and hurricanes affect dust mobilization in the Sahara-Sahel region. Furthermore, the 4He based record of dust flux suggests that dust export from the Sahara-Sahel region during the late 1880's was as high as that observed during the 1980's. Hence, high dust emissions from the Sahara-Sahel region in the latter part of the 20th century region were not unique events. Such observations have important implications in evaluating the role played by dust from North Africa in drying up of the Sahel and in understanding the feedback mechanisms of dust in the global climate system.
GC13A-0952
Trends in Streamflow in the Missouri River Basin from 1957 to 2006
The hydrologic consequences of the late 20th century atmospheric warming are of great interest to water managers and agricultural producers in the Northern Great Plains and the Missouri River Basin (MRB). For several other regions of North America, changes in streamflow characteristics are attributed to atmospheric warming, such as the earlier snowmelt runoff from the Sierra Nevada Mountains of California. The MRB streamflow record was examined for evidence of long-term trends in the mean annual flow, minimum flow, and seasonality for all stations (205) with continuous record for the last 50 years (1957-2006). Trends were statistically analyzed using the non-parametric Kendall Tau test. Fifty-five stations demonstrate an upward trend in streamflow, whereas 26 stations demonstrate a downward trend for the study period. No trends were significant for most stations, presumably due to the large interannual variability that is characteristic of the Northern Great Plains. Stations with trends are distributed in regional patterns. Downward streamflow trends were found in western Montana, Wyoming, Nebraska, and Kansas. Upward trends were found in North Dakota, South Dakota, Nebraska, and Iowa. Minimum flows for the period were examined using 62 stations of the Hydro-Climatic Data Network that have continuous record for the period 1957-2006. Twenty-one stations in North Dakota, South Dakota and Iowa demonstrate an upward trend of minimum flows. Three stations in Montana and Wyoming demonstrated a downward trend of minimum flows. Monthly streamflow records for the 205 stations were analyzed for seasonality using the temporal centroid of streamflow (CT) or center of mass approach. At 28 stations, runoff occurs earlier in the year. At six stations, runoff occurs later in the year but these sites are below reservoirs where changes in release patterns may explain the later trend.
GC13A-0953
Streamflow Interdecadal Variability Analysis for Rivers in Southern Chile and its Connections With Climate and Land-use Change
The time-series of annual and seasonal streamflow for 30 rivers in Southern Chile spanning five degrees latitude between VII Region of Maule and IX region of the Araucania ( -34°41' to -39°37') for different periods between 40 - 60 years are analyzed. The analysis includes application of the Multitaper Method (MTM) and the Maximum Entropy Method (MEM) to find the periodicities or interannual and decadal cycles. Previously SSA is applied in order to augment the signal-to-noise ratio. It is hypothesized that trends in streamflow are associated with the effect of climate change in Southern Chile, which predicts a decline in precipitation for higher latitudes; and cycles are related of the cycles of ENSO-3, SST, PDO and SOI. We also analyze the spatial variability using multivariate analysis. Analysis of the Maule region clearly shows two cycles significant at 95% confidence, 2 and 6 years. We have found that coastal watersheds present stronger streamflow variability between consecutives years than mountainous basins.
GC13A-0954
Trends in Stream Water Quality in the Southeastern United States
As part of the U.S Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Program water-quality data for 253 streams in 8 states of the Southeastern United States were assessed for trends from 1973-2005. Forty-three USGS sampling sites were examined for trends over multiple periods within 1973-2005 in measures of pH, specific conductance, and dissolved oxygen; and in concentrations of dissolved solids, suspended sediment, chloride, sodium, sulfate, silica, potassium, carbon, total nitrogen, total ammonia, total ammonia plus organic nitrogen, dissolved nitrite plus nitrate, and total phosphorus. An additional 210 sites from the U.S. Environmental Protection Agency STORET database were tested for trends in total nitrogen and total phosphorus concentrations over the 1975-2004 and 1993-2004 periods. The seasonal Kendall test or Tobit regression was used to detect monotonic trends. Concentrations of dissolved constituents have increased in many streams in the Southeast over the last 30 years. Specific conductance, an indicator of dissolved ions in water, increased in the Southeast in 26 USGS sites over the long term, but showed fewer increases in the 1993-2004 period. The pH increased at 11 of the 43 USGS sites in the Southeast from 1975 to 1985. Fewer trends in pH are apparent for 1993-2004. Concentrations of phosphorus in streams in the Southeast have decreased over the last 35 years coinciding with phosphate detergent bans and improvements in waste-water treatment that were implemented beginning in 1972. Sixteen of the 17 long-term trends in phosphorus concentrations detected at the 43 USGS sites were decreasing. Twenty-seven of the 32 long-term (1975-2004) trends detected in total phosphorus concentrations at the 210 STORET sites were decreasing. Nitrogen trends the Southeast are mixed. Decreasing trends in total nitrogen observed at USGS sites from 1975 to 1995 are not apparent during 1993-2004. Of the 18 recent (1993-2004) trends in total nitrogen detected at the 210 STORET sites, 13 were increasing trends. Ammonia concentrations decreased from 1973-2005 at 11 of the 43 USGS sites, and decreased in the more recent 1993-2004 period at 12 USGS sites. Nitrite plus nitrate concentrations decreased from 1973-2005 at 9 of the 43 USGS sites, and increased at 6 sites. A comparison of the USGS sites with multiple trend results for nitrate, ammonia plus organic nitrogen, ammonia and total nitrogen showed few associations. Trends in total nitrogen were directly related to changes in total ammonia plus organic nitrogen trends but not nitrate. This suggests that the principal change in stream nitrogen chemistry has been driven by a change in ammonia and organic nitrogen concentrations in streams, a change largely brought about by improved municipal waste-water treatment. A long-term water-quality and landscape trends-assessment network for the Southeast is needed to assess how water-quality changes over time in response to variation in population, agricultural, wastewater, and landscape variables. Understanding change in stream chemistry over time and its relationship with changes in population, agriculture, and waste-treatment technology in the Southeast will assist planners and water-resource managers in developing water-resource protection strategies.