Responses of the Pine Island and Thwaites Glaciers to Melt and Sliding Parameterizations

The Pine Island and Thwaites glaciers are the two largest contributors to sea level rise from Antarctica. Here we examine the influence of basal friction and ice shelf basal melt in determining projected losses. We examine both Weertman and Coulomb friction laws with explicit weakening as the ice thins to flotation, which many friction laws include implicitly via the effective pressure. We find relatively small differences with the choice of friction law (Weertman or Coulomb) but find losses to be highly sensitive to the rate at which the basal traction is reduced as the area upstream of the grounding line thins. Consistent with earlier work on Pine Island Glacier, we find sea level contributions from both glaciers to vary linearly with the melt volume averaged over time and space, with little influence from the spatial or temporal distribution of melt. Based on recent estimates of melt from other studies, our simulations suggest that the combined melt-driven and sea level rise contribution from both glaciers may not exceed 10 cm by 2200, although the uncertainty in model parameters allows for larger increases. We do not include other factors, such as ice shelf breakup, that might increase loss, or factors such as increased accumulation and isostatic uplift that may mitigate loss

Ice-shelf retreat drives recent Pine Island Glacier speedup

Speedup of Pine Island Glacier over the past several decades has made it Antarctica’s largest contributor to sea-level rise. The past speedup is largely due to grounding-line retreat in response to ocean-induced thinning that reduced ice-shelf buttressing. While speeds remained fairly steady from 2009 to late 2017, our Copernicus Sentinel 1A/B–derived velocity data show a >12% speedup over the past 3 years, coincident with a 19-km retreat of the ice shelf. We use an ice-flow model to simulate this loss, finding that accelerated calving can explain the recent speedup, independent of the grounding-line, melt-driven processes responsible for past speedups. If the ice shelf’s rapid retreat continues, it could further destabilize the glacier far sooner than would be expected due to surface- or ocean-melting processes

Oceanographic Controls on the Variability of Ice-Shelf Basal Melting and Circulation of Glacial Meltwater in the Amundsen Sea Embayment, Antarctica

Ice shelves in the Amundsen Sea Embayment have thinned, accelerating the seaward flow of ice sheets upstream over recent decades. This imbalance is caused by an increase in the ocean-driven melting of the ice shelves. Observations and models show that the ocean heat content reaching the ice shelves is sensitive to the depth of thermocline, which separates the cool, fresh surface waters from warm, salty waters. Yet the processes controlling the variability of thermocline depth remain poorly constrained. Here we quantify the oceanic conditions and ocean-driven melting of Cosgrove, Pine Island Glacier (PIG), Thwaites, Crosson, and Dotson ice shelves in the Amundsen Sea Embayment from 1991 to 2014 using a general circulation model. Ice-shelf melting is coupled to variability in the wind field and the sea-ice motions over the continental shelf break and associated onshore advection of warm waters in deep troughs. The layer of warm, salty waters at the calving front of PIG and Thwaites is thicker in austral spring (June–October) than in austral summer (December–March), whereas the seasonal cycle at the calving front of Dotson is reversed. Furthermore, the ocean-driven melting in PIG is enhanced by an asymmetric response to changes in ocean heat transport anomalies at the continental shelf break: melting responds more rapidly to increases in ocean heat transport than to decreases. This asymmetry is caused by the inland deepening of bathymetry and the glacial meltwater circulation around the ice shelf

Biodiversity recovery of Neotropical secondary forests

Old-growth tropical forests harbor an immense diversity of tree species but are rapidly being cleared, while secondary forests that regrow on abandoned agricultural lands increase in extent. We assess how tree species richness and composition recover during secondary succession across gradients in environmental conditions and anthropogenic disturbance in an unprecedented multisite analysis for the Neotropics. Secondary forests recover remarkably fast in species richness but slowly in species composition. Secondary forests take a median time of five decades to recover the species richness of old-growth forest (80% recovery after 20 years) based on rarefaction analysis. Full recovery of species composition takes centuries (only 34% recovery after 20 years). A dual strategy that maintains both old-growth forests and species-rich secondary forests is therefore crucial for biodiversity conservation in human-modified tropical landscapes. Copyright © 2019 The Authors, some rights reserved

Relationships between shallow-water cumacean assemblages and sediment characteristics facing the Iranian coast of the Persian Gulf

10 páginas, 8 figuras, 5 tablas.During two sampling campaigns carried out in August 1998 and November 2002, 232 cumaeans from eight species belonging to the families Bodotriidae and Nannastacidae were collected. This paper presents the first ecological data on a shallow water tropical cumacean assemblage from the Persian Gulf, where 50% of the existing species were recently described as new for the science. Neither the environmental conditions (except for the sediment organic content) nor the cumacean assemblage descriptors differed between the two sampling periods. However, two different species dominated in each period (i.e. Eocuma travancoricum and Heterocuma inerme in 1998 and 2002, respectively) and the MDS analysis revealed differences in the assemblage composition between periods, particularly for the deepest sampling stations. An increasing density together with the increase in gravel content, and a decreasing density together with the increasing silt content characterized the distribution pattern of both the whole cumacean assemblages and the two dominant species, the latter being also positively correlated with the mean grain size and negatively correlated with depth and organic matter (E. travancoricum) and with depth (H. inerme).The study was carried out within the frame of a project financed by TOTAL E&P (HSE Division) and is a contribution to the research contract between the CEAB (CSIC) and the French company CÉOCÉAN.Peer reviewe

Data associated with "Ice-Shelf Retreat Drives Recent Pine Island Glacier Speedup” and "Ocean-Induced Melt Volume Directly Paces Ice Loss from Pine Island Glacier "

Speedup of Pine Island Glacier over the last several decades has made it Antarctica’s largest contributor to sea-level rise. The past speedup is largely due to grounding-line retreat in response to ocean-induced thinning that reduced ice-shelf buttressing. These data are the model inputs and other observations associated with two papers that use an ice-flow model to investigate recent speedup of Pine Island Glacier, along with how continued melting may affect the glacier over the next 200 year

The genus Owenia (Annelida, Polychaeta) in the Persian Gulf, with description of a new species, Owenia persica.

Suplemento electronico correspondiente al artículo con el mismo título, publicado en Org. Divers. Evol. 6(4): 325–326 (no acesible sin subscripción) doi:10.1016/j.ode.2006.01.001Examination of a collection of Polychaeta from the Iranian coast of the Persian Gulf results in recognition of a new species of Owenia, namely O. persica sp. nov. This is an oculate oweniid (thorax width 0.27–1.17 mm) in which the collar edge is not rectilinear but presents an angle of 150° with an anterior opening. Hooks on the first abdominal segment are aligned at 45°. In lateral view, the upper teeth of the hooks’ head are clearly separated from the shaft; there is no discontinuity between the teeth, nuchal curve and shaft. The scales of the capillary chaetae are oval, with a long, loose transition between sections a and b, and short (a+b = 8.05 mm; ratio (a+b)/d = 7.76). The description of Owenia persica sp. nov contributes to the growing evidence that the cosmopolitan Owenia fusiformis sensu lato is, in fact, a complex of species. Two previous reports of O. fusiformis Delle Chiaje from the Gulf are shown to be misidentifications: the specimens from Kuwait clearly belong to O. persica sp. nov., whereas the single specimen from the Strait of Hormuz likely belongs to another new species, Owenia sp. The characteristics of the local distribution of O. persica sp. nov along the Iranian coast are analyzed on the basis of the available environmental data.Peer reviewe

Description of the new species Sigambra nkossa (Annelida, Pilargidae), with an analysis of the distribution patterns of polychaetes associated with artificially hydrocarbon-enriched bottoms

Este artículo contiene 31 páginas, 8 figuras.The monitoring of the N'Kossa offshore oil and gas fields in the Republic of Congo allowed us to assess the ecological traits of two polychaete species belonging to Sigambra (Annelida, Pilargidae). Sigambra parva occur in very low densities in all bottoms, except the most impacted, where it is totally absent; it is an undescribed species that reached >4,000 ind/m2 in hydrocarbon-enriched sediments. Their distribution patterns are compared with those of other polychaetes, showing a range of affinities for hydrocarbon-enriched sediments in the N'Kossa region. Our results suggest that S. parva would be a representative of the original local fauna, while the species associated with artificial hydrocarbon-enriched sediments, including the other Sigambra, six more polychaetes and a bivalve, could be natively associated with natural hydrocarbonenriched sediments, using the former as alternative habitats and as dispersal stepping stones. This ecological segregation, together with a careful morphological and morphometric analyses led us to describe the latter as a new species, namely Sigambra nkossa sp. nov. Moreover, morphometric analysis allowed us to discuss on the taxonomic robustness of the key morphological characters of S. nkossa sp. nov., as well as to emend the generic diagnosis of Sigambra to accommodate the new species.This article was funded by support given to Daniel Martin by the Consolidated Research Group on Marine Benthic Ecology of the Generalitat de Catalunya (Ref. 2017SGR378), the CSIC Intramural Project 201630E020, and the ongoing project ``Study of natural systems affected by coastal management and infrastructure projects in the open sea'' involving the CEAB-CSIC and CREOCEAN. João Gil was funded by a collaborative agreement signed with CREOCEAN. Daniel Martin received funds supporting the payment of the PeerJ publication fees through the CSIC Open Access Publication Support Initiative from the CSIC Unit of Information Resources for Research (URICI). TotalEnergies E&P Congo partly sponsored the field surveys.Peer reviewe

Macrobenthic densities and biomasess and sediment descriptors along a transect crossing the Gulf of Lions from the coast off Gruissan to the eastern side of the Gulf of Fos (French coast, NW Mediterranean)

This dataset includes the information from thirty-six samples collected in August 2014 from 12 stations along a transect crossing the Gulf of Lions, from the coast off Gruissan to the eastern side of the Gulf of Fos (French coast, NW Mediterranean). It includes the density and biomass of all microbenthic organisms collected (identified to the lowest taxonomic level). It also includes the information on the main variables describing the environmental characteristics of the samples stations: Latitude, Longitude, Distance, Depth, Escherichia coli, Enterococci, Silt, Clay, Very fine sands, Fines sands, Medium sands, Pore water, Organic Matter, Organic Carbon, Hydrocarbons C10-C40, Nitrogen, Phosphorous, Aluminium total, Arsenium total, Cadmium total, Chrome total, Copper total, Iron total, Mercury total, Nickel total, Lead total, Zinc total, HAPs, total PCBs, Acénaphtylène, Fluoranthène , Benzo (b) fluoranthène , Benzo (k) fluoranthène, Benzo (a) pyrène , Benzo (ghi) pérylène, Indéno (1,2,3 cd) pyrène, Anthracène, Acénaphtène, Chrysène, Dibenzo (a,h) anthracène, Fluorène, Naphtalène, Pyrène, Phénanthrène, Benzo (a) anthracène, PCB 28, PCB 52, PCB 101, PCB 118, PCB 138, PCB 153, PCB 180, PCB totaux calculés, Monobutylétain, Dibutylétain, Tributylétain, Triphénylétain.This dataset includes the information from thirty-six samples collected in August 2014 from 12 stations along a transect crossing the Gulf of Lions, from the coast off Gruissan to the eastern side of the Gulf of Fos (French coast, NW Mediterranean), and refers to the density and biomass per square metre of the macrobenthos, as well as to all common descriptors of the sediments, including organic and inorganic contaminants, and the most relevant sea surface satellite vaiables.Peer reviewe