ALBERT

Description: Time series (1990-2011) of sea ice thickness observed by moored sonars in the Transpolar Drift in Fram Strait are examined. Contrasting the post 2007 years against the 1990s, three remarkable changes in the monthly ice thickness distributions are highlighted: 1) The thickness of old level ice (modal thickness) is reduced by 32 percent, 2) the old ice modal peak width is reduced by 25 percent, and 3) the fraction of (ridged) ice thicker than 5 m is reduced by 50 percent. The combined effect on the mean ice thickness is a reduction from an annual average of 3.0 m during the 1990s to 2.2 m during 2008-2011. Most of the thinning took place after 2005-2006. While the old ice modal thickness and peak width show signs of recovery after 2008, the decreasing trend in fraction of ridged ice and mean ice thickness persists until the end of the record in 2011. The ice observed in Fram Strait carries an integrated signal of Arctic change due to the advection of ice from many sites in the Arctic. Based on concurrence in timing, we conclude that much of the thinning quantified here is reflecting recent change in the age composition of the Arctic ice cover towards younger ice. The old level ice remains thin, and as such the ice cover remains preconditioned for new summers of very low sea ice extent.

Description: Plasma cells produce and secrete massive amounts of disulfide-containing antibodies. To accommodate this load on the secretory machinery, the differentiation of resting B cells into antibody-secreting plasma cells is accompanied by a preferential expansion of the secretory compartments of the cells and by an up-regulation of enzymes involved in redox regulation and protein folding. We have quantified the absolute levels of protein thiols, protein disulfides, and glutathionylated proteins in whole cells. The results show that while the global thiol-disulfide state is affected to some extent by the differentiation, steady-state levels of glutathionylated protein thiols are less than 0.3% of the total protein cysteines, even in fully differentiated cells, and the overall protein redox state is not affected until late in differentiation, when large-scale IgM production is ongoing. A general expansion of the ER does not affect global protein redox status until an extensive production of cargo proteins has started.

Description: [1]  The Gamburtsev Subglacial Mountains (GSM), located near the center of East Antarctica, remain one of the most enigmatic mountain ranges on earth. A lack of direct geologic samples renders theirtectonic history almost totally unconstrained. We utilize teleseismic Rayleigh wave data from a two-year deployment of broadband seismic stations across the region to image shear velocity structure and analyze the lithospheric age of the GSM and surrounding regions. We solve for 2-D phase velocitiesand invert these results for 3-D shear velocity structure. We perform a Monte Carlo simulation to improve constraints of crustal thickness and shear velocity structure.Beneath the core of the GSM, we find crustal thickness in excess of 55 km.Mantle shear velocities remain faster than global average models to a depth of approximately 250 km, indicating a thick lithospheric root. Thinner crust and slower upper mantle velocities are observed beneath the Lambert Rift System and the Polar Subglacial Basin.When compared with phase velocity curves corresponding to specific tectonothermal ages elsewhere in the world, average phase velocity results for the GSM are consistent with regions of Archean – Paleoproterozoic origin. Combined with radiometric ages of detrital zircons found offshore, these results indicate a region of old crust that has undergone repeated periods of uplift and erosion, most recently during the Mesozoic breakup of Gondwana. Lower crustal seismic velocities imply a moderately dense lower crust beneath the core of the GSM, but with lower density than suggested by recent gravity models.

Description: Alongshore force balances, including the role of nonlinear advection, in the shoaling and surf zones onshore of a submarine canyon are investigated using a numerical modeling system (Delft3D/SWAN). The model is calibrated with waves and alongshore flows recorded over a period of 1.5 months at 26 sites along the 1.0-, 2.5-, and 5.0-m depth contours spanning about 2km of coast. Field-observation-based estimates of the alongshore pressure and radiation-stress gradients are reproduced well by the model. Model simulations suggest that the alongshore momentum balance is between the sum of the pressure and radiation-stress gradients and the sum of the nonlinear advective terms and bottom stress, with the remaining terms (e.g., wind stress and turbulent mixing) being negligible. The simulations also indicate that unexplained residuals in previous field-based estimates of the momentum balance may be owing to the neglect of the nonlinear advective terms, which are similar in magnitude to the sum of the forcing (pressure and radiations stress gradients) and to the bottom stress. This article is protected by copyright. All rights reserved.

Description: Nature Geoscience 8, 801 (2015). doi:10.1038/ngeo2539 Authors: Patrick L. Barnard, Andrew D. Short, Mitchell D. Harley, Kristen D. Splinter, Sean Vitousek, Ian L. Turner, Jonathan Allan, Masayuki Banno, Karin R. Bryan, André Doria, Jeff E. Hansen, Shigeru Kato, Yoshiaki Kuriyama, Evan Randall-Goodwin, Peter Ruggiero, Ian J. Walker & Derek K. Heathfield

Description: We examine the anthropogenically forced climate response for the twenty first century representative concentration pathway (RCP) emission scenarios and their extensions for the period 2101-2500. The experiments were performed with ModelE2, a new version of the NASA Goddard Institute for Space Sciences (GISS) coupled general circulation model that includes three different versions for the atmospheric composition components: a non-interactive version (NINT) with prescribed composition and a tuned aerosol indirect effect (AIE), the TCAD version with fully interactive aerosols, whole-atmosphere chemistry and the tuned AIE, and the TCADI version which further includes a parameterized first indirect aerosol effect on clouds. Each atmospheric version is coupled to two different ocean general circulation models: the Russell ocean model (GISS-E2-R) and HYCOM (GISS-E2-H). By 2100, global mean warming in the RCP scenarios ranges from 1.0ºC to 4.5ºC relative to 1850-1860 mean temperature in the historical simulations. In the RCP2.6 scenario, the surface warming in all simulations stays below a 2 °C threshold at the end of the twenty-first century. For RCP8.5, the range is 3.5-4.5ºC at 2100. Decadally averaged sea ice area changes are highly correlated to global mean surface air temperature anomalies and show steep declines in both hemispheres, with a larger sensitivity during winter months. By the year 2500, there are complete recoveries of the globally averaged surface air temperature for all versions of the GISS climate model in the low forcing scenario RCP2.6. TCADI simulations show enhanced warming due to greater sensitivity to CO 2 , aerosol effects and greater methane feedbacks and recovery is much slower in RCP2.6 than with the NINT and TCAD versions. All coupled models have decreases in the Atlantic overturning streamfunction by 2100. In RCP2.6 there is a complete recovery of the Atlantic overturning stream function by the year 2500 while with scenario RCP8.5, the E2-R climate model produces a complete shutdown of deep water formation in the North Atlantic. This article is protected by copyright. All rights reserved.

Description: We describe an experimental setup for making precision measurements of relative β -decay rates of 22 Na, 36 Cl, 54 Mn, 60 Co, 90 Sr, 133 Ba, 137 Cs, 152 Eu, and 154 Eu. The radioactive samples are mounted in two automated sample changers that sequentially position the samples with high spatial precision in front of sets of detectors. The set of detectors for one sample changer consists of four Geiger-Müller (GM) tubes and the other set of detectors consists of two NaI scintillators. The statistical uncertainty in the count rate is few times 0.01% per day for the GM detectors and about 0.01% per hour on the NaI detectors. The sample changers, detectors, and associated electronics are housed in a sealed chamber held at constant absolute pressure, humidity, and temperature to isolate the experiment from environmental variations. The apparatus is designed to accumulate statistics over many years in a regulated environment to test recent claims of small annual variations in the decay rates. We demonstrate that absent this environmental regulation, uncontrolled natural atmospheric pressure variations at our location would imprint an annual signal of 0.1% on the Geiger-Müller count rate. However, neither natural pressure variations nor plausible indoor room temperature variations cause a discernible influence on our NaI scintillator detector count rate.

Description: [1]  [1] The Gamburtsev Subglacial Mountains (GSM), located near the center of East Antarctica, are the highest feature within the East Antarctic highlands and have been investigated seismically for the first time during the 2007/2008 International Polar Year by the Gamburtsev Mountains Seismic Experiment. Using data from a network of 26 broadband seismic stations and body wave tomography, the P and S wave velocity structure of the upper mantle beneath the GSM and adjacent regions has been examined. Tomographic images produced from teleseismic P and S phases reveal several large-scale, small amplitude anomalies (δV p  = 1.0%, δV s  = 2.0%) in the upper 250 km of the mantle. The lateral distributions of these large-scale anomalies are similar in both the P and S wave velocity models and resolution tests show that they are well resolved. Velocity anomalies indicate slower, thinner lithosphere beneath the likely Meso- or Neoproterozoic Polar Subglacial Basin and faster, thicker lithosphere beneath the likely Archean/Paleoproterozoic East Antarctic highlands. Within the region of faster, thicker lithosphere, a lower amplitude (δV p  = 0.5%, δV s  = 1.0%) slow to fast velocity pattern is observed beneath the western flank of the GSM, suggesting a suture between two lithospheric blocks possibly of similar age. These findings point to a Precambrian origin for the high topography of the GSM, corroborating other studies invoking a long-lived highland landscape in central East Antarctica, as opposed to uplift caused by Permian/Cretaceous rifting or Cenozoic magmatism. The longevity of the GSM makes them geologically unusual, however, plausible analogues exist, such as the 550 Ma Petermann Ranges in central Australia. Additional uplift may have occurred by the reactivation of pre-existing faults, for example during the Carboniferous-Permian collision of Gondwana and Laurussia.

Description: Adaptive immunity is mediated by antigen receptors that can induce weak or strong immune responses depending on the nature of the antigen that is bound. In T lymphocytes, antigen recognition triggers signal transduction by clustering T cell receptor (TCR)/CD3 multiprotein complexes. In addition, it hypothesized that biophysical changes induced in TCR/CD3 that accompany receptor engagement may contribute to signal intensity. Nonclustering monovalent TCR/CD3 engagement is functionally inert despite the fact that it may induce changes in conformational arrangement or in the flexibility of receptor subunits. We report that the intrinsically inert monovalent engagement of TCR/CD3 can specifically enhance physiologic T cell responses to weak antigens in vitro and in vivo without stimulating antigen-unengaged T cells and without interrupting T cell responses to strong antigens, an effect that we term as "co-potentiation." We identified Mono-7D6-Fab, which biophysically altered TCR/CD3 when bound and functionally enhanced immune reactivity to several weak antigens in vitro, including a gp100-derived peptide associated with melanoma. In vivo, Mono-7D6-Fab induced T cell antigen–dependent therapeutic responses against melanoma lung metastases, an effect that synergized with other anti-melanoma immunotherapies to significantly improve outcome and survival. We conclude that Mono-7D6-Fab directly co-potentiated TCR/CD3 engagement by weak antigens and that such concept can be translated into an immunotherapeutic design. The co-potentiation principle may be applicable to other receptors that could be regulated by otherwise inert compounds whose latent potency is only invoked in concert with specific physiologic ligands.

Description: The Transantarctic Mountains (TAMs) are the largest non-collisional mountain range on Earth. Their origin, as well as the origin of the Wilkes Subglacial Basin (WSB) along the inland side of the TAMs, have been widely debated, and a key constraint to distinguish between competing models is the underlying crustal structure. Previous investigations have examined this structure but have primarily focused on a small region of the central TAMs near Ross Island, providing little along-strike constraint. In this study, we use data from the new Transantarctic Mountains Northern Network and from five stations operated by the Korea Polar Research Institute to investigate the crustal structure beneath a previously unexplored portion of the TAMs. Using S-wave receiver functions and Rayleigh wave phase velocities, crustal thickness and average crustal shear velocity ( ) are resolved within ±4 km and ±0.1 km/s, respectively. The crust thickens from ~20 km near the Ross Sea coast to ~46 km beneath the northern TAMs, which is somewhat thicker than that imaged in previous studies beneath the central TAMs. The crust thins to ~41 km beneath the WSB. ranges from ~3.1-3.9 km/s, with slower velocities near the coast. Our findings are consistent with a flexural origin for the TAMs and WSB, where these features result from broad flexure of the East Antarctic lithosphere and uplift along its western edge due to thermal conduction from hotter mantle beneath West Antarctica. Locally thicker crust may explain the ~1 km of additional topography in the northern TAMs compared to the central TAMs.