Will coastal wetlands continue to sequester carbon in response to an increase in global sea level?: a case study of the rapidly subsiding Mississippi river deltaic plain

The highly visible coastal phenomenon of wetland loss in coastal Louisiana (LA) was examined through the prism of carbon accumulation and loss. Carbon storage or sequestration in rapidly subsiding LA coastal marsh soils was based on vertical marsh accretion and aerial change data. Marshes sequester significant amount of carbon through vertical accretion however, large amounts of carbon previously sequestration in the soil profile is lost through annual deterioration of these coastal marshes. Hurricanes, such as Katrina and Rita, have triggered instantaneous large carbon losses of sequestered soil carbon through the destruction of large areas of marsh. This analysis shows proposed coastal restoration efforts will not be sufficient to restore carbon losses by storms and marsh deterioration. Further, we have estimated the economic benefit of carbon sequestration for coastal wetland restoration efforts. Results show that LA coastal marshes may not serve as a net sink of carbon. These results may serve as a predictor of the impact of future predictions of increasing global sea level rise on carbon sequestration for other coastal regions.     

OCS,H2S,and CS2 fluxes from a salt water marsh

The diurnal-to-monthly behavior of the fluxes of OCS, H₂S, and CS₂ from a mixed-Spartina grass-covered site in a Wallops Island salt water marsh was determined through a series of experiments in August and September, 1982. Absolute flux values were determined for OCS and H₂S, while only relative values were determined for CS₂. The rates of emission of OCS and H₂S were observed to vary diurnally and to be strongly influenced by tides. The time-averaged flux values show that such mixed-Spartina stands are insignificant ( 1%) global sources of H₂S or CS₂ and insignificant contributors to the global OCS cycle (< 1%). These results demonstrate that some marsh regions play a minor role in the global sulfur budget and, consequently, that the inclusion of such areas in extrapolations of measurements of more productive regions could lead to an overestimate of the role of salt water marshes in the global sulfur budget.     

新疆湿地资源时空变化特征及其原因分析研究

以新疆第一次（2000年）和第二次（2011年）湿地资源调查中相同的347块湿地为研究对象,利用3S技术,对CBERS、SPOT5和LandsatTM遥感数据进行调查监测,并结合野外实地验证,比较分析新疆湿地资源的时空变化状况及其原因。结果表明,新疆湿地总面积呈减少的趋势,其中河流湿地和沼泽湿地面积增加,分别增加29162 hm²和17130 hm²,湖泊湿地和人工湿地面积减少,分别减少126618 hm²和19391 hm²;各湿地型中,永久性河流、草本沼泽、森林沼泽和季节性咸水沼泽面积有所增加,洪泛平原、内陆盐沼、永久性 淡水湖、季节性淡水湖、季节性咸水湖和库塘湿地面积减少。新疆湿地面积总变化率-7%,各湿地类型中,面积变化率最大的是湖泊湿地（18%）,呈减少趋势;最小的是沼泽湿地（5%）,呈增加趋势。湿地面积变化的主要原因是气候变化和人类活动。     

The Impacts of Socioeconomic Development and Climate Change on Severe Weather Catastrophe Losses: Mid-Atlantic Region (MAR) and the U.S.

One strand of research relates the magnitude of severe weather disasters to climatic and human development factors; another highlights dramatic growth in catastrophe losses. However, there have been few attempts to put the two strands together. Here we use an explicit modeling framework to determine the contribution of climate variability relative to human factors in reported catastrophe losses. We then examine how future climate change can be expected to affect losses from natural disasters. Simultaneous regression models are constructed from three equations in which the dependent variables are U.S. flood loss, U.S. hurricane loss and U.S. catastrophe loss. Then two kinds of simulation under two climate change scenarios explore how climate change would affect losses. The climate change scenarios respectively project 13.5% and 21.5% increases in annual precipitation. The first simulation increases only the mean value of annual precipitation; the second simulation assumes that the mean and standard deviation of annual precipitation change in the same proportion. Results show that the growth in reported losses from weather-related natural disasters is due mainly to three socioeconomic factors: inflation, population growth and growth in per capita real wealth. However, weather variables such as precipitation and the number of hurricanes per period also clearly affect losses. The three stage least squares (3SLS) simultaneous equation model shows that a 1% increase in annual precipitation would enlarge catastrophe loss by as much as 2.8%. These findings are suggestive as planning signals to decision makers.     

A warm and wet little climatic optimum and a cold and dry little ice age in the southern rocky mountains,U.S.A.

The zenith of Anasazi Pueblo Indian occupation in the northern Colorado Plateau region of the southwestern U.S.A. coincides with the Little Climatic Optimum or Medieval Warm Period (A.D. 900–1300), and its demise coincides with the commencement of the Little Ice Age. Indexes of winter (jet-stream derived) and summer (monsoon derived) precipitation and growing season length were developed for the La Plata Mountains region of southwestern Colorado. The results show that during the height of the Little Climatic Optimum (A.D. 1000–1100) the region was characterized by a relatively long growing season and by a potential dry farming zone or elevational belt (currently located between 2,000 m and 2,300 m elevation) that was twice as wide as present and could support Anasazi upland dry farming down to at least 1,600 m, an elevation that is quite impossible to dry farm today because of insufficient soil moisture. This expanded dry-farm belt is attributable to a more vigorous circulation regime characterized by both greater winter and summer precipitation than that of today. Between A.D. 1100 and 1300 the potential dry-farm belt narrowed and finally disappeared with the onset of a period of markedly colder and drier conditions than currently exist. Finally, when the Little Ice Age terminated in the mid A.D. 1800s and warmer, wetter conditions returned to the region, another group of farmers (modern Anglos) were able to dry farm the area.The U.S. Government right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.     

Past and future plant diversity of a coastal wetland driven by soil subsidence and climate change

On the island of Ameland (The Netherlands), natural gas has been extracted from a dune and salt marsh natural area since 1986. This has caused a soil subsidence of c. 1–25?cm, which can be used as a model to infer effects of future sea level rise. The aims of our study were (a) to relate the changes in the vegetation, and more specifically, in plant diversity, during the extraction period to soil subsidence and weather fluctuations, and (b) to use these relations to predict future changes due to the combination of ongoing soil subsidence and climate change. We characterised climate change as increases in mean sea level, storm frequency and net precipitation. Simultaneous observations were made of vegetation composition, elevation, soil chemistry, net precipitation, groundwater level, and flooding frequency over the period 1986–2001. By using multiple regression the changes in the vegetation could be decomposed into (1) an oscillatory component due to fluctuations in net precipitation, (2) an oscillatory component due to incidental flooding, (3) a monotonous component due to soil subsidence, and (4) a monotonous component not related to any measured variable but probably due to eutrophication. The changes were generally small during the observation period, but the regression model predicts large changes by the year 2100 that are almost exclusively due to sea level rise. However, although sea level rise is expected to cause a loss of species, this does not necessarily lead to a loss of conservancy value.     

Characterizing the distribution of observed precipitation and runoff over the continental United States

This paper describes the development of a comprehensive geographic database of historical precipitation and runoff measurements for the conterminous U.S. The database is used in a spatial analysis to characterize large scale precipitation and runoff patterns and to assess the utility and limitations of using historical hydro-meteorological data for providing spatially distributed precipitation estimates at regional and continental scales. Long-term annual average precipitation (P) and runoff (Q) surfaces (geographically referenced, digital representations of a continuous spatial distribution) generated from interpolation of point measurements are used in a distributed water balance calculation to check the reliability of precipitation estimates. The resulting input-output values (P- Q) illustrate the deficiency (sparse distribution and low elevation bias) of historical precipitation measurements in the mountainous western U.S. where snowmelt is an important component of the annual runoff. The incorporation of high elevation snow measurements into the precipitation record significantly improves the water balance estimates in some areas and enhances the utility of historical data for providing spatially distributed precipitation estimates in topographically diverse regions. Regions where the use of historical precipitation data may be most limited for precipitation estimation are identified and alternatives to the use of interpolated historical data for precipitation estimation across large heterogenous regions are suggested. The research establishes a database for continental scale studies and provides direction for the successful development of spatially distributed regional scale water balance models.     

Interactions between Habitat Loss and Climate Change: Implications for Fairy Shrimp in the Central Valley Ecoregion of California, Usa

Combinations of habitat loss and climate change can alter the distribution of environmental conditions available to organisms. The magnitude and direction of these changes may have important implications for ecological processes and species persistence. This study explored the potential impacts of projected changes in climate and land-use for five fairy shrimp species (Crustacea: Anostraca) endemic to vernal pools in the Central Valley ecoregion of California, U.S.A. Scenarios describing habitat extent and climate were developed for 2040 and 2100 and compared to a 1990s baseline. Hydrologic conditions in vernal pools were found to be sensitive to projected climate changes, and, in the absence of habitat loss, warmer temperatures and greater winter precipitation would drive vernal pools toward longer, more frequent periods of inundation. However, existing biological reserves for three of the five species are biased toward drier areas and if unprotected habitat were lost, the net change in hydrologic conditions would be reversed with remaining habitat providing shorter, less frequent inundations. Species with unbiased representation in reserves do not show this reversal, and they have predictable shifts in hydrologic conditions. These results demonstrate the importance of biologically and climatically representative reserve systems under climate change and habitat loss.     

Taking the Pulse of Mountains: Ecosystem Responses to Climatic Variability

An integrated program of ecosystem modeling and field studies in the mountains of the Pacific Northwest (U.S.A.) has quantified many of the ecological processes affected by climatic variability. Paleoecological and contemporary ecological data in forest ecosystems provided model parameterization and validation at broad spatial and temporal scales for tree growth, tree regeneration and treeline movement. For subalpine tree species, winter precipitation has a strong negative correlation with growth; this relationship is stronger at higher elevations and west-side sites (which have more precipitation). Temperature affects tree growth at some locations with respect to length of growing season (spring) and severity of drought at drier sites (summer). Furthermore, variable but predictable climate-growth relationships across elevation gradients suggest that tree species respond differently to climate at different locations, making a uniform response of these species to future climatic change unlikely. Multi-decadal variability in climate also affects ecosystem processes. Mountain hemlock growth at high-elevation sites is negatively correlated with winter snow depth and positively correlated with the winter Pacific Decadal Oscillation (PDO) index. At low elevations, the reverse is true. Glacier mass balance and fire severity are also linked to PDO. Rapid establishment of trees in subalpine ecosystems during this century is increasing forest cover and reducing meadow cover at many subalpine locations in the western U.S.A. and precipitation (snow depth) is a critical variable regulating conifer expansion. Lastly, modeling potential future ecosystem conditions suggests that increased climatic variability will result in increasing forest fire size and frequency, and reduced net primary productivity in drier, east-side forest ecosystems. As additional empirical data and modeling output become available, we will improve our ability to predict the effects of climatic change across a broad range of climates and mountain ecosystems in the northwestern U.S.A.     

Evaluation of Hydrologically Relevant PCM Climate Variables and Large-Scale Variability over the Continental U.S.

The ability of the Parallel Climate Model (PCM) to reproduce the mean and variability of hydrologically relevant climate variables was evaluated by comparing PCM historical climate runs with observations over temporal scales from sub-daily to annual. The domain was the continental U.S, and the model spatial resolution was T42 (about 2.8 degrees latitude by longitude). The climate variables evaluated include precipitation, surface air temperature, net surface solar radiation, soil moisture, and snow water equivalent. The results show that PCM has a winter dry bias in the Pacific Northwest and a summer wet bias in the central plains. The diurnal precipitation variation in summer is much stronger than observed, with an afternoon maximum in summer precipitation over much of the U.S. interior, in contrast with an observed nocturnal maximum in parts of the interior. PCM has a cold bias in annual mean temperature over most of the U.S., with deviations as large as ?8 K. The PCM daily temperature range is lower than observed, especiallyin the central U.S. PCM generally overestimates the net solar radiation over most of the U.S, although the diurnal cycle is simulated well in spring, summer and winter. In autumn PCM has a pronounced noontime peak in solar radiation that differs by 5–10% from observations. PCM'ssimulated soil moisture is less variable than that of a sophisticated land-surface hydrology model, especially in the interior of the country. PCM simulates the wetter conditions over the southeastern U.S. and California during warm (El Niño) events, but shifts the drier conditions in the PacificNorthwest northward and underestimates their magnitude. The temperature response to the North Pacific Oscillation is generally captured by PCM, but the amplitude of this response is overestimated by a factor of about two.     

RECENT TRENDS IN TREE-RING RECORDS FROM HIGH ELEVATION SITES IN THE ANDES OF NORTHERN PATAGONIA

A new set of tree-ring records from the Andes of northern Patagonia, Argentina (41° S) was used to evaluate recent (i.e., last 250 years) regional trends in tree growth at upper treeline. Fifteen tree-ring chronologies from 1200 to 1750 m elevation were developed for Nothofagus pumilio, the dominant subalpine species. Samples were collected along three elevational transects located along the steep west-to-east precipitation gradient from the main Cordillera (mean annual precipitation >4000 mm) to an eastern outlier of the Andes (mean annual precipitation >2000 mm). Ring-width variation in higher elevation tree-ring records from the main Cordillera is mainly related to changes in temperature and precipitation during spring and summer. However, the response to climatic variation is also influenced by local site factors of elevation and exposure. Based on the relationships between Nothofagus growth and climate, we reconstructed changes in snow cover duration in late spring and variations in mean annual temperature since A.D. 1750. Abrupt interannual changes in the mean annual temperature reconstruction are associated with strong to very strong El Niño-Southern Oscillation events. At upper treeline, tree growth since 1977 has been anomalously high. A sharp rise in global average tropospheric temperatures has been recorded since the mid-1970s in response to an enhanced tropical hydrologic cycle due to an increase in temperature of the tropical Pacific. Temperatures in northern Patagonia have been anomalously high throughout the 1980s, which is consistent with positive temperature anomalies in the tropical Pacific and along the western coast of the Americas at c.a. 40° S latitude. Our 250-year temperature reconstruction indicates that although the persistently high temperatures of the 1980s are uncommon during this period, they are not unprecedented. Tropical climatic episodes similar to that observed during the 1980s may have occurred in the recent past under pre-industrial carbon dioxide levels.     

Incorporating uncertainty of future sea-level rise estimates into vulnerability assessment: A case study in Kahului, Maui

Accurate sea-level rise (SLR) vulnerability assessments are essential in developing effective management strategies for coastal systems at risk. In this study, we evaluate the effect of combining vertical uncertainties in Light Detection and Ranging (LiDAR) elevation data, datum transformation and future SLR estimates on estimating potential land area and land cover loss, and whether including uncertainty in future SLR estimates has implications for adaptation decisions in Kahului, Maui. Monte Carlo simulation is used to propagate probability distributions through our inundation model, and the output probability surfaces are generalized as areas of high and low probability of inundation. Our results show that considering uncertainty in just LiDAR and transformation overestimates vulnerable land area by about 3 % for the high probability threshold, resulting in conservative adaptation decisions, and underestimates vulnerable land area by about 14 % for the low probability threshold, resulting in less reliable adaptation decisions for Kahului. Not considering uncertainty in future SLR estimates in addition to LiDAR and transformation has variable effect on SLR adaptation decisions depending on the land cover category and how the high and low probability thresholds are defined. Monte Carlo simulation is a valuable approach to SLR vulnerability assessments because errors are not required to follow a Gaussian distribution.     

Radiation balance over a salt marsh

Linear relationships have been found between daytime incoming radiation and both net radiation and reflected radiation over a Spartina alterniflora salt marsh at North Inlet, S.C., during the summer. On the average, using total daytime values, net radiation was 70 ± 9% and reflected radiation was 9 ± 1% of incoming radiation.     

Potential Atmospheric Transport Pathways for Mercury Measured in the Canadian High Arctic

Large-scale transport pathways for atmospheric gaseous mercury emitted from surrounding source regions to reach the Alert sampling site located at the Northwest Territories of Canada between August 1992 and August 1993 were investigated. The 12-month atmospheric mercury data set comprises blank-corrected total gaseous mercury (TGM) concentrations collected on gold-coated sand traps during one-week long sampling intervals. For TGM concentrations above the 12-month mean TGM level, the analysis reveals regions in Eastern Europe (close to East Germany and Poland), areas on Northeastern America in Canada (Northwest Territories), and central Siberia of the former U.S.S.R. Identification of the physical locations of the emission sources was limited by the temporal resolution of weekly averaged data; however, major atmospheric pathways of mercury transport to the Arctic were successfully resolved. The objective of this note is to demonstrate that the potential source contribution function could be applied to resolve the sources and recover transport pathways of atmospheric mercury over a large scale.     

Analysis of non-linear inundation from sea-level rise using LIDAR data: a case study for South Florida

By analyzing a digital elevation model (DEM) derived from airborne light detection and ranging (LIDAR) data and airborne height finder measurements, this study demonstrates that a 1.5 m sea-level rise by 2100 would cause inundation of large areas of Miami-Dade County, southern Broward County, and Everglades National Park. Inundation processes are non-linear: inundation is gradual before reaching a threshold, and speeds up rapidly afterwards due to the regional topography. Accelerated sea-level rise will cause the threshold to be reached sooner by amplifying the non-linear inundation, and must be considered in policy-making. Comparison of inundated areas extracted from 30 m LIDAR and USGS DEMs indicates that the vertical accuracy of a DEM has a great effect on delineation of inundation areas. For a 1.5 m sea-level rise, the inundated area delineated by USGS DEM for Broward County is 1.65 times greater than that indicated by the LIDAR DEM.     

Atmospheric moisture budget and its regulation of the summer precipitation variability over the Southeastern United States

Atmospheric moisture budget and its regulation of the summer (June–July–August) precipitation over the Southeastern United State (SE U.S.) were examined during 1948–2007 using PRECipitation REConstruction over Land and multiple reanalysis datasets. The analysis shows that the interannual variation of SE U.S. summer precipitation can be largely explained by the leading Empirical Orthogonal Function mode showing a spatially homogenous sub-continental scale pattern. Consequently, areal-averaged precipitation was investigated to focus on the large-scale rainfall changes over the SE U.S. The wavelet analysis identifies an increased 2–4 year power spectrum in recent 30 years (1978–2007), suggesting an intensification of the interannual variability. Analysis of the atmospheric moisture budget indicates that the increase in precipitation variability is mainly caused by moisture transport, which exhibits a similar increase in the 2–4 year power spectrum for the same period. Moisture transport, in turn, is largely controlled by the seasonal mean component rather than the subseasonal-scale eddies. Furthermore, our results indicate that dynamic processes (atmospheric circulation) are more important than thermodynamic processes (specific humidity) in regulating the interannual variation of moisture transport. Specifically, the North Atlantic Subtropical High western ridge position is found to be a primary regulator, with the ridge in the northwest (southwest) corresponding to anomalous moisture divergence (convergence) over the SE U.S. Changes in moisture transport consistent with the increased frequency of these two ridge types in recent 30 years favor the intensification of summer precipitation variability.     

A national approach to greenhouse gas abatement through blue carbon management

There is increasing interest in protecting, restoring and creating ‘blue carbon’ ecosystems (BCE; mangroves, tidal marshes and seagrasses) to sequester atmospheric CO₂-C and thereby contribute to climate change mitigation. While a growing number of countries aspire to report greenhouse gas emission and carbon sequestration changes from these ecosystems under voluntary international reporting requirements, few countries have domestic policy frameworks that specifically support the quantification and financing of carbon emission abatement through BCE management.Australia, as home to approximately 5–11% of global blue carbon stocks, has a substantial interest in the development of blue carbon policy. Here we assess the potential inclusion of blue carbon within Australia's Emissions Reduction Fund, emphasizing issues and approaches that have global relevance. We used a participatory workshop of scientific experts and carbon industry stakeholders to identify blue carbon management actions that would meet the requirements of the Fund. In total, twelve actions were assessed for their greenhouse gas emission abatement potential and the ability to measure abatement reliably, using a combination of available data and qualitative and quantitative methods, including expert knowledge.We identify and discuss the five most relevant and promising activities, encompassing the protection, restoration and creation of mangroves, tidal marshes and seagrasses. On a per area basis, mean abatement intensity of organic carbon (C_org) was highest for the (re)introduction of tidal flow resulting in establishment of mangrove (13–15 Mg C_org ha⁻¹ yr⁻¹) and tidal marsh (6–8 Mg C_org ha⁻¹ yr⁻¹), followed by land use planning for sea-level rise for the creation of new mangrove habitat (8 Mg C_org ha⁻¹ yr⁻¹). The avoided disturbance of existing mangroves, tidal marshes and seagrasses has the twofold benefit of avoiding remineralisation of existing stocks, plus the future annual abatement associated with the net sequestration of atmospheric CO₂-C as C_org with the continued functioning of these BCE. Our approach offers a template that uses best available information to identify options for carbon abatement through management of coastal landscapes, and details current knowledge gaps and important technical aspects that need to be considered for implementation in carbon crediting schemes.     

Impact of moisture flux convergence and soil moisture on precipitation: a case study for the southern United States with implications for the globe

Interactions between soil moisture, evapotranspiration (ET), atmospheric moisture fluxes and precipitation are complex. It is difficult to attribute the variations of one variable to another. In this study, we investigate the influence of atmospheric moisture fluxes and land surface soil moisture on local precipitation, with a focus on the southern United States (U.S.), a region with a strong humidity gradient and intense moisture fluxes. Experiments with the Weather Research and Forecasting model show that the variation of moisture flux convergence (MFC) is more important than that of soil moisture for precipitation variation over the southern U.S. Further analyses decompose the precipitation change into several contributing factors and show that MFC affects precipitation both directly through changing moisture inflow (wet areas) and indirectly by changing the precipitation efficiency (transitional zones). Soil moisture affects precipitation mainly by changing the precipitation efficiency, and secondly through direct surface ET contribution. The greatest soil moisture effects are over transitional zones. MFC is more important for the probability of heavier rainfall; soil moisture has much weaker impact on rainfall probability and its roles are similar for the probability of intermediate-to-heavy rainfall (>10 mm day^?1). Although MFC is more important than soil moisture for precipitation over most regions, the impact of soil moisture could be large over certain transitional regions. At the submonthly time scale, the African Sahel appears to be the only major region where soil moisture has a greater impact than MFC on precipitation. This study provides guidance to understanding and further investigation of the roles of local land surface processes and large-scale circulations on precipitation.     

西藏高原测站降水与TRMM估测降水一致性评估

利用124个测站2011—2012年6—8月逐小时降水资料,分辨率为0.25°×0.25°的TRMM估测降水和DEM 高程数据,采用相关系数、相对误差和准确性指标,分析了西藏高原TRMM估测降水整体表现能力及海拔高度对降水估测影响。结果表明：TRMM估测降水在西藏高原整体趋势较一致,降水量级偏大,次数偏多;平均无降水准确率远高于平均有降水准确率,漏测率低而空测率高,降水量大的测站TRMM估测能力相对强。西藏高原上大部分测站处于相对低洼（河谷）地带,海拔高度差较小的区域TRMM估测降水与测站降水误差小,较大的区域误差则大。     

Interannual variability and correlation of vegetation cover and precipitation in Eastern China

Based on the SPOT/VEGETATION Normalized Difference Vegetation Index (NDVI) data and daily precipitation data of 357 meteorological stations, the spatial and temporal variability of vegetation cover, measured by NDVI, and precipitation as well as their relationships are investigated in Eastern China, which is portioned into three subregions (regions I, II, and III), for the period 1998–2010. The results show that high NDVI values appear mainly in Northeastern China and in August while high precipitation (PRETOT) occurs in Southeastern China and in July (June for Southern China). Extreme precipitation days (RD95p) and amount (EPRETOT) coincide well with PRETOT. Extreme precipitation intensity (RINTEN) has a similar spatial variability to PRETOT but with a smaller seasonal variation than PRETOT. Growing season NDVI is positively correlated with PRETOT in 11.7 % of the study area (mostly in arid to subhumid regions of Northern China), where precipitation is a limiting factor for vegetation growth. In contrast, a negative correlation between growing season NDVI and PRETOT is found in 4.8 % of the study area, mostly in areas around the Yangtze River and deep Northeastern China. No significant correlations between these two variables are found for the other regions because vegetation response to precipitation is affected by other factors such as temperature, radiation, and human disturbance. On a monthly scale, there is a positive correlation between NDVI and PRETOT in May (for region II) and September (all subregions except region I). NDVI variations lag 1 month behind PRETOT in June (for region I) and October. Correlations between NDVI and RD95p, EPRETOT are similar to that with PRETOT, but the relationships between NDVI and RINTEN are relatively weaker than with PRETOT. This study provides the technical basis for agriculture development and ecological construction in Eastern China.