Utility of late summer transient snowline migration rate on Taku Glacier, Alaska

On Taku Glacier, Alaska a combination of field observations of snow water equivalent (SWE) from snowpits and probing in the vicinity of the transient snowline (TSL) are used to quantify the mass balance gradient. The balance gradient derived from the TSL and SWE measured in snowpits at 1000 m from 1998–2010 ranges from 2.6–3.8 mm m<sup>−1</sup>. Probing transects from 950 m–1100 m directly measure SWE and yield a slightly higher balance gradient of 3.3–3.8 mm m<sup>−1</sup>. The TSL on Taku Glacier is identified in MODIS and Landsat 4 and 7 Thematic Mapper images for 31 dates during the 2004–2010 period to assess the consistency of its rate of rise and reliability in assessing ablation for mass balance assessment. For example, in 2010, the TSL was 750 m on 28 July, 800 m on 5 August, 875 m on 14 August, 925 m on 30 August, and 975 m on 20 September. The mean observed probing balance gradient was 3.3 mm m<sup>−1</sup>, combined with the TSL rise of 3.7 m day<sup>−1</sup> yields an ablation rate of 12.2 mm day<sup>−1</sup> from mid-July to mid-Sept, 2010. The TSL rise in the region from 750–1100 m on Taku Glacier during eleven periods each covering more than 14 days during the ablation season indicates a mean TSL rise of 3.7 m day<sup>−1</sup>, the rate of rise is relatively consistent ranging from 3.1 to 4.4 m day<sup>−1</sup>. This rate is useful for ascertaining the final ELA if images or observations are not available near the end of the ablation season. The mean ablation from 750–1100 m during the July–September period determined from the TSL rise and the observed balance gradient is 11–13 mm day<sup>−1</sup> on Taku Glacier during the 2004–2010 period. The potential for providing an estimate of b<sub>n</sub> from TSL observations late in the melt season from satellite images combined with the frequent availability of such images provides a means for efficient mass balance assessment in many years and on many glaciers

Glacier annual balance measurement, prediction, forecasting and climate correlations, North Cascades, Washington 1984?2006

International audienceNorth Cascade glacier annual balance measured on 10 glaciers from 1984?2006 yielded mean annual balance (ba) of ?0.54 m/a, and ?12.38 m cumulatively. This is a significant loss for glaciers that average 30?60 m in thickness, representing 20?40% of their entire volume. Two observed glaciers, Lewis Glacier and Spider Glacier, no longer exist. The ba of North Cascade glaciers is reliably calculated based on 1 April snowpack water equivalent and ablation season temperature. 1 May forecasting of ba using the Pacific Decadal Oscillation and the Multivariate El Nino Southern Oscillation circulation indices correctly determined the sign of mass balance in 42 of 47 years. Glacier annual balance forecasting is an important step for summer water resource management in glacier runoff dominated stream systems. The forecast for North Cascade glaciers in 2007 is for a negative annual balance

Glacier annual balance measurement, forecasting and climate correlations, North Cascades, Washington 1984?2006

International audienceNorth Cascade glacier annual balance measured on 10 glaciers from 1984?2006 yielded mean annual balance (ba) of ?0.54 m/a, and ?12.38 m cumulatively. This is a significant loss for glaciers that average 30?60 m in thickness, 20?40% of their entire volume. Two observed glaciers, Lewis Glacier and Spider Glacier, no longer exist. The ba of North Cascade glaciers is reliably calculated, correlation coefficient 0.91, using 1 April snowpack water equivalent and ablation season temperature. Utilizing ba from 10 glaciers 1984?2006 and net balance (bn) from South Cascade 1960?2005, a set of forecast rules for glacier mass balance were derived utilizing October?April Pacific Decadal Oscillation and Multivariate El Nino Southern Oscillation index values. The forecast rules provide a correct assessment in 41 of the 46 years for South Cascade Glacier and 20 of 23 years for NCGCP glaciers. Glacier annual balance forecasting is an important step for summer water resource management in glacier runoff dominated stream systems. The forecast for North Cascade glaciers in 2007 is for a negative ba

Sedimentological, Geochemical and Isotopic Evidence for the Establishment of Modern Circulation through the Bering Strait and Depositional Environment History of the Bering and Chukchi Seas during the Last Deglaciation

Sea level regression during the Last Glacial Maximum exposed the Bering Land Bridge, and cut off the connection between the North Pacific and Arctic Ocean, ending the exchange of North Pacific Water through the Bering Strait. Exchange of North Pacific Water comprises a major portion of fresh water input to the Arctic Ocean, and is of vital importance to North Atlantic Deep Water formation, a vital component of Atlantic Meridional Overturning Circulation. Bering Strait throughflow thus plays an integral role in global climate stability. A suite of four cores was selected, three in the Bering Sea and one in the Chukchi Sea, to bracket the Bering Strait in order to elucidate changes in sediment delivery, productivity and regional oceanography as the Bering Land Bridge flooded and modern ocean circulation was established during the last deglaciation. The arrival of nutrient rich North Pacific Water in the Chukchi Sea is recorded around 8 ka by organic carbon isotope depletion and an increase in total organic carbon and organic nitrogen, reflecting an increasingly marine isotopic signal and increased productivity. In the Bering Sea, the early deglaciation is marked by depleted organic carbon isotopes that indicate increasing terrestrial input, and increased total organic carbon. Principal component analysis of sedimentologic, geochemical and isotopic data clearly captures discrete sediment populations that correspond to key climatic intervals, representing changes in sediment delivery, productivity and circulation during the last deglaciation. In the Bering Sea we observe that deglaciation began in earnest around 18–17 ka, but lack of confidence in our age control does not allow for a precise date. Our results suggest that modern circulation through the Bering Strait, and thus for the Bering and Chukchi Seas, was established ~8 ka. Prior to 8 ka there is an interval of sediment that appears record a possible reversal of flow through the Bering Strait corresponding to the 8.2 ka event

Identification of the Staphylococcal Cassette Chromosome Mec (SCCmec) element in viral fractions from environmental samples

Antibiotic resistance attributed to methicillin-resistant Staphylococcus aureus (MRSA) has become a growing concern over the last decade in both the healthcare and agricultural environment. This resistance is encoded by the gene mecA that is located on a mosaic, mobile genetic element called the Staphylococcal Cassette Chromosome mec (SCCmec) element. It is proposed that the transfer of the SCCmec element and resulting spread of resistance occur by transduction, the transfer of genetic material from bacterium to bacterium by a bacteriophage. Specifically, it is hypothesized that the transduction of this resistance is occurring in the agricultural setting. To test this, a protocol was optimized to allow for an efficient filtration of the environmental samples and a high yield of concentrated viral DNA. It was determined that 22% of the total samples collected contained either the mec gene or the ccr gene, while 9% of the total samples contained both antibiotic resistance genes. While it was determined that the protocol did not affect the generation of a PCR product, inhibition PCR manifested the presence of inhibitors in different samples, which may have contributed to a “negative” PCR product. These findings manifested the presence of methicillin resistance in environmental samples from local areas in Virginia. These results have direct implications on antibiotic use in agriculture and should be a cause for alarm

The equilibrium flow and mass balance of the Taku Glacier, Alaska 1950?2006

International audienceThe Taku Glacier, Alaska has advanced 7.5 km since the late nineteenth century, while all other primary outlet glaciers of the Juneau Icefield are in retreat. The Juneau Icefield Research Program has completed field work on the Taku Glacier annually since 1946. The collected observations of surface mass balance, glacier velocity and glacier thickness at Profile IV 29 km above the terminus and 4 km above the equilibrium line provide a means to assess the equilibrium nature of the Taku Glacier. Velocity measured over a twelve month span and annual summer velocity measurements completed at a Profile IV from 1950?2006 indicate insignificant variations in velocity seasonally or from year to year. The consistency of velocity over the 56-year period indicates that in the vicinity of the equilibrium line, the flow of the Taku Glacier has been in an equilibrium state. Surface mass balance was positive from 1946?1988 averaging +0.42 m a?1. This led to glacier thickening. From 1988?2006 an important change has occurred and annual balance has been ?0.14 m a?1, and the glacier thickness has ceased increasing along Profile IV. Field measurements of ice depth and surface velocity allow calculation of the volume flux at Profile IV. Volume flux is then compared with the surface balance flux from the region of the glacier above Profile IV, determined annually in the field. Above Profile IV the observed mean surface flux is 5.50×108 m3/a (±5%), while the calculated volume flux range flowing through profile IV is 5.00?5.47×108 m3/a. The mean surface flux has been greater than the volume flux, which has led to slow thickening of the Taku Glacier up to 1988. The thickening has not led to a change in the flow of Taku Glacier at Profile IV

An improved lower bound for (1,<=2)-identifying codes in the king grid

We call a subset $C$ of vertices of a graph $G$ a $(1,\leq \ell)$-identifying code if for all subsets $X$ of vertices with size at most $\ell$, the sets $\{c\in C |\exists u \in X, d(u,c)\leq 1\}$ are distinct. The concept of identifying codes was introduced in 1998 by Karpovsky, Chakrabarty and Levitin. Identifying codes have been studied in various grids. In particular, it has been shown that there exists a $(1,\leq 2)$-identifying code in the king grid with density 3/7 and that there are no such identifying codes with density smaller than 5/12. Using a suitable frame and a discharging procedure, we improve the lower bound by showing that any $(1,\leq 2)$-identifying code of the king grid has density at least 47/111

Sptrx-2, a fusion protein composed of one thioredoxin and three tandemly repeated NDP-kinase domains is expressed in human testis germ cells

42 páginas, 9 figuras.Background Thioredoxins (Trx) are small redox proteins that function as general protein disulphide reductases and regulate several cellular processes such as transcription factor DNA binding activity, apoptosis and DNA synthesis. In mammalian organisms, thioredoxins are generally ubiquitously expressed in all tissues, with the exception of Sptrx-1 which is specifically expressed in sperm cells. Results We report here the identification and characterization of a novel member of the thioredoxin family, the second with a tissue-specific distribution in human sperm, termed Sptrx-2. The Sptrx-2 ORF (open reading frame) encodes for a protein of 588 amino acids with two different domains: an N-terminal thioredoxin domain encompassing the first 105 residues and a C-terminal domain composed of three repeats of a NDP kinase domain. The Sptrx-2 gene spans about 51 kb organized in 17 exons and maps at locus 7p13-14. Sptrx-2 mRNA is exclusively expressed in human testis, mainly in primary spermatocytes, while Sptrx-2 protein expression is detected from the pachytene spermatocytes stage onwards, peaking at round spermatids stage. Recombinant full-length Sptrx-2 expressed in bacteria displayed neither thioredoxin nor NDP kinase enzymatic activity. Conclusions The sperm specific expression of Sptrx-2, together with its chromosomal assignment to a position reported as a potential locus for flagellar anomalies and male infertility phenotypes such as primary ciliary dyskinesia, suggests that it might be a novel component of the human sperm axonemal organization.This work was supported by grants from the Swedish Medical Research Council (Projects 03P-14096-01A, 03X-14041-01A and 13X-10370), the Åke Wibergs Stiftelse, the Karolinska Institutet, the Södertörns Högskola and the Medical Research Fund of Tampere University Hospital.Peer reviewe

Glaciers in the Canadian Columbia Basin, Technical Report

The cryosphere - all forms of frozen water on Earth- plays a fundamental role in its climate system. Seasonal snow, mountain glaciers, ice sheets, and sea ice reflect much of the incoming shortwave radiation at high latitudes and in mountainous terrain back to space, helping to regulate the surface temperature of the planet. Accelerating concentrations of greenhouse gases (Solomon et al. 2009) are responsible for late twentieth and early twenty-first century tropospheric warming; this warming in turn drives large-scale changes in the cryosphere, with global implications that include changes in hemispheric circulation (Francis and Vavrus 2012), sea level rise (Gardner et al. 2013) and increased warming through ice-albedo feedbacks