BFM-SI: A new implementation of the biogeochemical flux model in sea ice

This work describes a novel implementation of the Biogeochemical Flux Model (BFM) in a sea ice system (BFMSI). The chosen representative groups of the sea ice food web rely on the same dynamics as the BFM. The main differences between BFM and BFMSI stand in the type and number of functional groups, in the parameters assigned to several physiological and ecological processes and in the dimensional size classes they represent. The differential equations of BFMSI are written here according to the nomenclature associated to the new sea ice state variables. At the boundaries, the sea ice system is also coupled to the atmosphere and to the ocean through the exchange of organic and inorganic matter. This is done by computing the entrapment of particulate and dissolved matter and gases when sea ice grows and release to the ocean when sea ice melts to ensure mass conservation. The implementation of the BFM in sea ice and the coupling structure in General Circulation Models will add a new component that may provide new adequate estimate of the role and importance of sea ice biogeochemistry in the global carbon cycle

Simulated Greenland Surface Mass Balance in the GISS ModelE2 GCM: Role of the Ice Sheet Surface

The rate of growth or retreat of the Greenland and Antarctic ice sheets remains a highly uncertain component of future sea level change. Here we examine the simulation of Greenland ice sheet surface mass balance (GrIS SMB) in the NASA Goddard Institute for Space Studies (GISS) ModelE2 General Circulation Model (GCM). GCMs are often limited in their ability to represent SMB compared with polarregion Regional Climate Models (RCMs). We compare ModelE2 simulated GrIS SMB for presentday (19962005) simulations with fixed ocean conditions, at a spatial resolution of 2 latitude by 2.5 longitude (~200 km), with SMB simulated by the Modle Atmosphrique Rgionale (MAR) RCM (19962005 at a 25 km resolution). ModelE2 SMB agrees well with MAR SMB on the whole, but there are distinct spatial patterns of differences and large differences in some SMB components. The impact of changes to the ModelE2 surface are tested, including a subgridscale representation of SMB with surface elevation classes. This has a minimal effect on ice sheetwide SMB, but corrects local biases. Replacing fixed surface albedo with satellitederived values and an agedependent scheme has a larger impact, increasing simulated melt by 60100%. We also find that lower surface albedo can enhance the effects of elevation classes. Reducing ModelE2 surface roughness length to values closer to MAR reduces sublimation by ~50%. Further work is required to account for meltwater refreezing in ModelE2, and to understand how differences in atmospheric processes and model resolution influence simulated SMB

Arctic cut-off high drives the poleward shift of a new Greenland melting record

Large-scale atmospheric circulation controls the mass and energy balance of the Greenland ice sheet through its impact on radiative budget, runoff and accumulation. Here, using reanalysis data and the outputs of a regional climate model, we show that the persistence of an exceptional atmospheric ridge, centred over the Arctic Ocean, was responsible for a poleward shift of runoff, albedo and surface temperature records over the Greenland during the summer of 2015. New records of monthly mean zonal winds at 500 hPa and of the maximum latitude of ridge peaks of the 5,700±50 m isohypse over the Arctic were associated with the formation and persistency of a cutoff high. The unprecedented (1948–2015) and sustained atmospheric conditions promoted enhanced runoff, increased the surface temperatures and decreased the albedo in northern Greenland, while inhibiting melting in the south, where new melting records were set over the past decade

Increased Greenland melt triggered by large-scale, year-round cyclonic moisture intrusions

Surface melting is a major driver of Greenland's mass loss. Yet, the mechanisms that trigger melt are still insufficiently understood because seasonally based studies blend processes initiating melt with positive feedbacks. Here, we focus on the triggers of melt by examining the synoptic atmospheric conditions associated with 313 rapid melt increases, detected in a satellite-derived melt extent product, equally distributed throughout the year over the period 1979–2012. By combining reanalysis and weather station data, we show that melt is initiated by a cyclone-driven, southerly flow of warm, moist air, which gives rise to large-scale precipitation. A decomposition of the synoptic atmospheric variability over Greenland suggests that the identified, melt-triggering weather pattern accounts for ∼40&thinsp;% of the net precipitation, but increases in the frequency, duration and areal extent of the initiated melting have shifted the line between mass gain and mass loss as more melt and rainwater run off or accumulate in the snowpack. Using a regional climate model, we estimate that the initiated melting more than doubled over the investigated period, amounting to ∼28&thinsp;% of the overall surface melt and revealing that, despite the involved mass gain, year-round precipitation events are participating in the ice sheet's decline.</p

Diagnosing the extreme surface melt event over southwestern Greenland in 2007

Abstract. Analysis of passive microwave brightness temperatures from the space-borne Special Sensor Microwave Imager (SSM/I) documents a record surface snowmelt over high elevations (above 2000 m) of the Greenland ice sheet during summer of 2007. To interpret this record, results from the SSM/I are examined in conjunction with fields from the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis and output from a regional climate model. The record surface melt reflects unusually warm conditions, seen in positive summertime anomalies of surface air temperatures, downwelling longwave radiation, 1000–500 hPa atmospheric thickness, and the net surface energy flux, linked in turn to southerly airflow over the ice sheet. Low snow accumulation may have contributed to the record through promoting anomalously low surface albedo

A remark on the BRST symmetry in the Gribov-Zwanziger theory

We show that the soft breaking of the BRST symmetry arising in the Gribov-Zwanziger theory can be converted into a linear breaking upon introduction of a set of BRST quartets of auxiliary fields. Due to its compatibility with the Quantum Action Principle, the linearly broken BRST symmetry can be directly converted into a suitable set of useful Slavnov-Taylor identities. As a consequence, it turns out that the renormalization aspects of the Gribov-Zwanziger theory can be addressed by means of the cohomology of a nilpotent local operatorComment: 11 pages, final version to appear in Phys. Rev.

Fe(II) and Mn(II) removal from contaminated groundwater by adsorption. A comparison of activated carbon and pine bark

This paper aims to compare the adsorption performance of activated carbon and pine bark for iron and manganese removal from contaminated groundwater. Moreover, their environmental compatibility was checked for their possible use as reactive media in a permeable reactive barrier for in situ remediation. Batch tests were carried out with different iron and manganese concentrations and different particle-size distributions, in order to evaluate the effectiveness of the activated carbon and pine bark on removal depending on both the initial pollutant concentration and the surface area of the adsorbent. High removal efficiencies were reached by both of the reactive media. However, faster removal at higher concentration was observed only for iron adsorption by activated carbon. The particle-size distribution did not significantly influence the process in the experimental conditions tested. The immobilization process on the reactive media can be considered almost irreversible since the quantities of iron and manganese released during the desorption tests were negligible