Evidence for atmospheric control of sea-ice motion through Nares Strait

Satellite observations of ice motion are combined with model estimates of low‐level winds and surface wind stress to provide evidence for atmospheric control of sea‐ice motion through Nares Strait, between Ellesmere Island and Greenland, during two periods in 2004. The results suggest that ice flux through the strait, and its shutdown through the formation of a landfast ice mass in the strait, can be controlled by wind stress and atmospheric cooling. Analysis of the model results during these two periods also suggest that the intense, low‐level, along‐strait winds are strongly ageostrophic, and may be usefully estimated from pressure differences along the Strait

An RNA Transport System in Candida albicans Regulates Hyphal Morphology and Invasive Growth

Localization of specific mRNAs is an important mechanism through which cells achieve polarity and direct asymmetric growth. Based on a framework established in Saccharomyces cerevisiae, we describe a She3-dependent RNA transport system in Candida albicans, a fungal pathogen of humans that grows as both budding (yeast) and filamentous (hyphal and pseudohyphal) forms. We identify a set of 40 mRNAs that are selectively transported to the buds of yeast-form cells and to the tips of hyphae, and we show that many of the genes encoded by these mRNAs contribute to hyphal development, as does the transport system itself. Although the basic system of mRNA transport is conserved between S. cerevisiae and C. albicans, we find that the cargo mRNAs have diverged considerably, implying that specific mRNAs can easily move in and out of transport control over evolutionary timescales. The differences in mRNA cargos likely reflect the distinct selective pressures acting on the two species

Daughter-Specific Transcription Factors Regulate Cell Size Control in Budding Yeast

The asymmetric localization of cell fate determinants results in asymmetric cell cycle control in budding yeast

Effect of Dietary Zinc Oxide on Morphological Characteristics, Mucin Composition and Gene Expression in the Colon of Weaned Piglets

The trace element zinc is often used in the diet of weaned piglets, as high doses have resulted in positive effects on intestinal health. However, the majority of previous studies evaluated zinc supplementations for a short period only and focused on the small intestine. The hypothesis of the present study was that low, medium and high levels of dietary zinc (57, 164 and 2,425 mg Zn/kg from zinc oxide) would affect colonic morphology and innate host defense mechanisms across 4 weeks post-weaning. Histological examinations were conducted regarding the colonic morphology and neutral, acidic, sialylated and sulphated mucins. The mRNA expression levels of mucin (MUC) 1, 2, 13, 20, toll-like receptor (TLR) 2, 4, interleukin (IL)-1β, 8, 10, interferon-γ (IFN-γ) and transforming growth factor-β (TGF-β) were also measured. The colonic crypt area increased in an age-depending manner, and the greatest area was found with medium concentration of dietary zinc. With the high concentration of dietary zinc, the number of goblet cells containing mixed neutral-acidic mucins and total mucins increased. Sialomucin containing goblet cells increased age-dependently. The expression of MUC2 increased with age and reached the highest level at 47 days of age. The expression levels of TLR2 and 4 decreased with age. The mRNA expression of TLR4 and the pro-inflammatory cytokine IL-8 were down-regulated with high dietary zinc treatment, while piglets fed with medium dietary zinc had the highest expression. It is concluded that dietary zinc level had a clear impact on colonic morphology, mucin profiles and immunological traits in piglets after weaning. Those changes might support local defense mechanisms and affect colonic physiology and contribute to the reported reduction of post-weaning diarrhea

Pathways of meltwater export from Petermann Glacier, Greenland

Intrusions of Atlantic Water cause basal melting of Greenlands marine terminating glaciers and ice shelves such as that of Petermann Glacier, in northwest Greenland. The fate of the resulting glacial meltwater is largely unknown. It is investigated here, using hydrographic observations collected during a research cruise in Petermann Fjord and adjacent Nares Strait on board I/B Oden in August 2015. A three end-member mixing method provides the concentration of Petermann ice shelf meltwater. Meltwater from Petermann is found in all of the casts in adjacent Nares Strait, with highest concentration along the Greenland coast in the direction of Kelvin wave phase propagation. The meltwater from Petermann mostly flows out on the northeast side of the fjord as a baroclinic boundary current, with the depth of maximum meltwater concentrations approximately 150 m and shoaling along its pathway. At the outer sill, which separates the fjord from the ambient ocean, approximately 0.3 mSv of basal meltwater leaves the fjord at depths between 100 and 300 m. The total geostrophic heat and freshwater fluxes close to the glacier’s terminus in August 2015 were similar to those estimated in August 2009, before the two major calving events that reduced the length of Petermann’s ice tongue by nearly a third, and despite warmer inflowing Atlantic Water. These results provide a baseline, but also highlight what is needed to assess properly the impact on ocean circulation and sea level of Greenland’s mass loss as the Atlantic Water warms up

Pathways of meltwater export from Petermann Glacier, Greenland

Intrusions of Atlantic Water cause basal melting of Greenlands marine terminating glaciers and ice shelves such as that of Petermann Glacier, in northwest Greenland. The fate of the resulting glacial meltwater is largely unknown. It is investigated here, using hydrographic observations collected during a research cruise in Petermann Fjord and adjacent Nares Strait on board I/B Oden in August 2015. A three end-member mixing method provides the concentration of Petermann ice shelf meltwater. Meltwater from Petermann is found in all of the casts in adjacent Nares Strait, with highest concentration along the Greenland coast in the direction of Kelvin wave phase propagation. The meltwater from Petermann mostly flows out on the northeast side of the fjord as a baroclinic boundary current, with the depth of maximum meltwater concentrations approximately 150 m and shoaling along its pathway. At the outer sill, which separates the fjord from the ambient ocean, approximately 0.3 mSv of basal meltwater leaves the fjord at depths between 100 and 300 m. The total geostrophic heat and freshwater fluxes close to the glacier’s terminus in August 2015 were similar to those estimated in August 2009, before the two major calving events that reduced the length of Petermann’s ice tongue by nearly a third, and despite warmer inflowing Atlantic Water. These results provide a baseline, but also highlight what is needed to assess properly the impact on ocean circulation and sea level of Greenland’s mass loss as the Atlantic Water warms up

Semidiurnal switching of stratification in the Region of Freshwater Influence of the Rhine

Observations in the Rhine region of freshwater influence (ROFI) system in the North Sea show evidence of large semidiurnal oscillations in stability, superimposed on a mean stratification, occurring throughout the stratified region at times of reduced mixing. The amplitude of this semidiurnal variation is of the same order as the mean stability and frequently results in conditions being mixed or nearly mixed once per tide. It is deduced that this semidiurnal variation results primarily from cross-shore tidal straining which interacts with the density gradient to induce stratification. This conceptual picture of the contributing processes has been tested in a one-dimensional point model forced by the observed slopes and the local density gradients. The model exhibits the same qualitative behavior as the observations, produces oscillations in stratification of the amplitude observed, and confirms the critical role of cross-shore tidal straining. The large cross-shore shear nder stratified conditions is identified with the changes in ellipse configuration which are observed between mixed and stratified conditions. The occurrence of semidiurnal variations in stability in the Rhine ROFI is thus inferred to be a consequence of the development of mean stability whenever the horizontal density gradients relax in conditions of low stirring

Controls of Stratification the Rhine ROFI

combined effect of tidal, wind and wave stirring which, at times, brings about complete vertical homogeneity. Control by the mixing variables has been elucidated by a regression analysis of mean stratification on the components of the windstress and significant wave height. There is strong partial correlation with all three variables which explains between 56% and 65% of the variance in two time series of observations in October 1990 and September 1992, respectively. During periods of low stirring the water column was observed to re-stratify over the whole inshore region through the relaxation of the horizontal gradients under gravity and with the influence of rotation. Superimposed on the mean stratification there is strong semi-diurnal variation, occurring throughout the stratified region at times of reduced mixing. The amplitude of this semi-diurnal variation is of the same order as the mean stability and frequently results in conditions being mixed or nearly mixed once per tide. This semi-diurnal variation results primarily from cross-shore tidal straining which interacts with the main density gradient to induce stratification. The hypothesis that water column stability is controlled by the combination of these processes has been tested using a reduced physics model which has been successful in reproducing the main features of both the mean and semi-diurnal components of stratification