Understanding hydrological processes in glacierized catchments: Evidence and implications of highly variable isotopic and electrical conductivity data

The spatial and temporal characterization of geochemical tracers over Alpine glacierized catchments is particularly difficult, but fundamental to quantify groundwater, glacier melt, and rain water contribution to stream runoff. In this study, we analysed the spatial and temporal variability of δ²H and electrical conductivity (EC) in various water sources during three ablation seasons in an 8.4‐km² glacierized catchment in the Italian Alps, in relation to snow cover and hydro‐meteorological conditions. Variations in the daily streamflow range due to melt‐induced runoff events were controlled by maximum daily air temperature and snow covered area in the catchment. Maximum daily streamflow decreased with increasing snow cover, and a threshold relation was found between maximum daily temperature and daily streamflow range. During melt‐induced runoff events, stream water EC decreased due to the contribution of glacier melt water to stream runoff. In this catchment, EC could be used to distinguish the contribution of subglacial flow (identified as an end member, enriched in EC) from glacier melt water to stream runoff, whereas spring water in the study area could not be considered as an end member. The isotopic composition of snow, glacier ice, and melt water was not significantly correlated with the sampling point elevation, and the spatial variability was more likely affected by postdepositional processes. The high spatial and temporal variability in the tracer signature of the end members (subglacial flow, rain water, glacier melt water, and residual winter snow), together with small daily variability in stream water δ²H dynamics, are problematic for the quantification of the contribution of the identified end members to stream runoff, and call for further research, possibly integrated with other natural or artificial tracers.     

Highly localised distribution patterns of juvenile sea cucumber Australostichopus mollis

Information on the environmental characteristics of the juvenile habitat of many deposit-feeding sea cucumber species is limited, despite most fished species exhibiting rapid localised depletion. The current study combined large and small scale surveying techniques within a New Zealand harbour to identify areas with high densities of juvenile Australostichopus mollis, a commercially valuable aspidochirote holothurian. Data from detailed surveys were used to relate densities of juveniles and adults with measures of physical habitat characteristics including depth, sediment facies type, grain size range, as well as measures of chlorophyll-a, phaeopigment, carbon and nitrogen content of surface sediment. Results revealed a highly localised distribution of juvenile A. mollis focused on one site associated with an area of high adult density. Sites of high juvenile A. mollis density were characterised by sediment qualities favouring epibenthic detritivorous deposit feeding, including high nitrogen content, high phaeopigment:chlorophyll-a ratio and small grain size. The high-density juvenile site had facies that were further characterised by the presence of large shell fragments (>10 cm length) of the horse mussel (Atrina zelandica), which may provide a unique settlement microhabitat for early juveniles. Unlike some other sea cucumber species, juvenile A. mollis shows no distinct spatial separation from adult sea cucumbers, no association with dense macroalgae and no clear preference for shallower depths than adults. Overall, the results illustrate the highly localised pattern of recruitment of this species to a widely distributed adult population, which may help to explain the lack of previous observations of juveniles in this species. These results indicate the importance of identifying and protecting what appear to be very specific juvenile habitats in deposit-feeding sea cucumbers to ensure continuing recruitment to exploited populations.     

Current Behaviour and Dynamics of the Lowermost Italian Glacier (Montasio Occidentale,Julian Alps)

Smaller glaciers (<0.5 km²) react quickly to environmental changes and typically show a large scatter in their individual response. Accounting for these ice bodies is essential for assessing regional glacier change, given their high number and contribution to the total loss of glacier area in mountain regions. However, studying small glaciers using traditional techniques may be difficult or not feasible, and assessing their current activity and dynamics may be problematic. In this paper, we present an integrated approach for characterizing the current behaviour of a small, avalanche‐fed glacier at low altitude in the Italian Alps, combining geomorphological, geophysical and high‐resolution geodetic surveying with a terrestrial laser scanner. The glacier is still active and shows a detectable mass transfer from the accumulation area to the lower ablation area, which is covered by a thick debris mantle. The glacier owes its existence to the local topo‐climatic conditions, ensured by high rock walls which enhance accumulation by delivering avalanche snow and reduce ablation by providing topographic shading and regulating the debris budget of the glacier catchment. In the last several years the glacier has displayed peculiar behaviour compared with most glaciers of the European Alps, being close to equilibrium conditions in spite of warm ablation seasons. Proportionally small relative changes have also occurred since the Little Ice Age maximum. Compared with the majority of other Alpine glaciers, we infer for this glacier a lower sensitivity to air temperature and a higher sensitivity to precipitation, associated with important feedback from increasing debris cover during unfavourable periods.     

Recognizing Carbon Forestry’s Uneven Geography: A Response to Purdon and the Structure-Agency Dichotomy That Never Was

We here respond to the critique by Purdon of an article on carbon forestry that we published in this journal last year (Carton and Andersson). While we welcome critical engagements with our work, Purdon’s argument is wide of the mark and appears based largely on misconceptions regarding our theoretical entry point and empirical findings. Underlying this are fundamental disagreements about the nature of carbon forestry, structure-agency dynamics, and how to understand environmental interventions in the global South more broadly. We argue that we are unlikely to “find common ground” in our respective analyses of the Trees for Global Benefits project unless we share a common understanding of the unequal power relations and fundamental geographical unevenness within which carbon projects operate. Contrary to what Purdon argues, this position has nothing to do with ignoring local benefits, nor with denying the agency of the smallholder farmers who participate in the project. We see no contradiction between an analysis that does justice to the various structural conditions that frame carbon forest projects, and a recognition of local agency.     

Where Forest Carbon Meets Its Maker: Forestry-Based Offsetting as the Subsumption of Nature

ABSTRACT

The “subsumption of nature” framework focuses on productivity increases and extractive innovations in nature-based industries. In this article, we argue that it can also be employed beyond that context in order to capture the convoluted dynamics of market environmentalism. To substantiate our argument, we draw on recent fieldwork on “Trees for Global Benefits,” a forestry-based offsetting project in western Uganda. Like industrial tree plantations, this project relies on the subsumption of carbon sequestration to market imperatives in order to guarantee the quality of its carbon credits. The ecological and socioeconomic difficulties this process engenders give rise to unintended consequences and set in motion the disciplining of the carbon offset producers themselves. The application of the subsumption framework to nonindustrial sectors in this way calls attention to the interlinked socioecological dynamics involved in the subsumption of nature, and highlights potential synergies with previous work on the subsumption of labor.     

Interaction between an eddy and a zonal jet : Part II. Two-and-a-half-layer model

In a two-and-a-half-layer quasi-geostrophic model, a process study is conducted on the interaction between a vortex and a zonal jet, both with constant potential vorticity. The vortex is a stable anticyclone, initially located north of the eastward jet. The potential vorticity of the jet is allowed to have various vertical structures, while the vortex is concentrated in only one layer. The flow parameters are set to values characteristic of the Azores region.First, the jet is stable. Weak vortices steadily drift north of the jet without crossing it while strong vortices can cross the jet and tear off a cyclone with which they pair as a heton (baroclinic dipole). This heton often breaks later in the shear exerted by the jet; the two vortices finally drift apart. When crossed by deep anticyclones, the jet develops meanders with 375 km wavelength. These results exhibit a noticeable similarity with the one-and-a-half-layer case studied in Part I.Secondly, the jet is allowed to be linearly unstable. In the absence of the vortex, it develops meanders with 175 km wavelength and 25-day e-folding time on the β-plane. For various vertical structures of the jet, baroclinic instability is shown to barely affect jet–vortex interaction if the linear growth rate of unstable waves is smaller than 1/(14 days). Further simulations with a linearly unstable, nonlinearly equilibrated jet evidence its strong temporal variability when crossed by a deep vortex on the β-plane. In particular, long waves can dominate the spectrum for a few months after jet crossing by the vortex. Again in this process, the deep vortex couples with a surface cyclone and both drift southwestward.     

Comparison of retrospective analyses of the global ocean heat content

In this study, we compare seven retrospective analyses of basin- to global-scale upper ocean temperature. The analyses span a minimum of 10 years during the 50-year period since World War II. Three of the analyses (WOA-94, WHITE, BMRC) are based on objective analysis and thus, do not rely on a numerical forecast model. The remaining four (NCEP, WAJSOWICZ, ROSATI, SODA) are based on data assimilation in which the numerical forecast is provided by some form of the Geophysical Fluid Dynamics Laboratory Modular Ocean Model driven by historical winds. The comparison presented here is limited to heat content in the upper 250 m, information that is available for all analyses. The results are presented in three frequency bands: seasonal, interannual (periods of 1–5 years), and decadal (periods of 5–25 years). At seasonal frequencies, all of the analyses are quite similar. Otherwise, the differences among analyses are limited to the regions of the western boundary currents, and some regions in the Southern Hemisphere. At interannual frequencies, significant differences appear between the objective analyses and the data assimilation analyses. Along the equator in the Pacific, where variability is dominated by El Niño, the objective analyses have somewhat noisier fields, as well as reduced variance prior to 1980 due to lack of observations. Still, the correlation among analyses generally exceeds 80% in this region. Along the equator in the Atlantic, the correlation is lower (30–60%) although inspection of the time series shows that the same biennial progression of warm and cool events appears in all analyses since 1980. In the midlatitude Pacific agreement among objective analyses and data assimilation analyses is good. The analysis of Rosati et al. [Rosati, A., Gudgel, R., Miyakoda, K., 1995. Decadal analysis produced from an ocean assimilation system. Mon. Weather Rev., 123, 2, 206.] differs somewhat from the others apparently because in this analysis, the forecast model is weighted more heavily relative to the observations. The analysis of Levitus et al. [Levitus, S., Boyer, T.P., Antonov, J., 1994. Interannual variability of upper ocean thermal structure. World Ocean Atlas, 1994, Vol. 5. Natl. Env. Satell. Data and Int. Serv., Natl. Oceanic and Atmos. Admin. Atlas series, Washington, DC, 176 pp.] has a much different spatial distribution of variability in the interannual band than the others. Partly, this results from the yearly time-averaging of this analysis. Three of the monthly analyses extend over 20 years and thus are useful for examining decadal variations. Comparison of these analyses shows in common a slow progression of warm water westward and then eastward along the equator in the tropical Pacific that is linked to the decadal fluctuations of El Niño.     

Western boundary upwelling dynamics off Oman

Despite its climatic and ecosystemic significance, the coastal upwelling that takes place off Oman is not well understood. A primitive-equation, regional model forced by climatological wind stress is used to investigate its dynamics and to compare it with the better-known Eastern Boundary Upwellings (EBUs). The solution compares favorably with existing observations, simulating well the seasonal cycles of thermal structure, surface circulation (mean and turbulent), and sea-surface temperature (SST). There is a 1.5-month lag between the maximum of the upwelling-favorable wind-stress-curl forcing and the oceanic response (minima in sea-surface height and SST), which we attribute to onshore-propagating Rossby waves. A southwestward-flowing undercurrent (opposite to the direction of the near-surface flow) is also simulated with a core depth of 1000 m, much deeper than found in EBUs (150–200 m). An EKE budget reveals that, in contrast to EBUs, the upwelling jet is more prone to barotropic than baroclinic instability and the contribution of locally-generated instabilities to EKE is higher by an order of magnitude. Advection and redistribution of EKE by standing mesoscale features also play a significant role in EKE budget.     

Laboratory performances of the solar multichannel resonant scattering spectrometer prototype of the GOLF‐New Generation instrument

This article quickly summarizes the performances and results of the GOLF/SoHO resonant spectrometer, thus justifying to go a step further. We then recall the characteristics of the multichannel resonant GOLF‐NG spectrometer and present the first successful performances of the laboratory tests on the prototype and also the limitations of this first technological instrument. Scientific questions and an observation strategy are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)