SFTA2 - a novel secretory peptide highly expressed in the lung - is modulated by lipopolysaccharide but not hyperoxia

Tissue-specific transcripts are likely to be of importance for the corresponding organ. While attempting to define the specific transcriptome of the human lung, we identified the transcript of a yet uncharacterized protein, SFTA2. In silico analyses, biochemical methods, fluorescence imaging and animal challenge experiments were employed to characterize SFTA2. Human SFTA2 is located on Chr. 6p21.33, a disease-susceptibility locus for diffuse panbronchiolitis. RT-PCR verified the abundance of SFTA2-specific transcripts in human and mouse lung. SFTA2 is synthesized as a hydrophilic precursor releasing a 59 amino acid mature peptide after cleavage of an N-terminal secretory signal. SFTA2 has no recognizable homology to other proteins while orthologues are present in all mammals. SFTA2 is a glycosylated protein and specifically expressed in nonciliated bronchiolar epithelium and type II pneumocytes. In accordance with other hydrophilic surfactant proteins, SFTA2 did not colocalize with lamellar bodies but colocalized with golgin97 and clathrin-labelled vesicles, suggesting a classical secretory pathway for its expression and secretion. In the mouse lung, Sfta2 was significantly downregulated after induction of an inflammatory reaction by intratracheal lipopolysaccharides paralleling surfactant proteins B and C but not D. Hyperoxia, however, did not alter SFTA2 mRNA levels. We have characterized SFTA2 and present it as a novel unique secretory peptide highly expressed in the lung

TIFAX 2011 Summer Campaign - Sea ice thickness measurements with Polar 5 from Station Nord and Svalbard

During the last decade, an increased advection of thick multi-year ice that originates from an area north of Greenland, out of the Arctic through Fram Strait was observed. A replacement of this old and thick sea ice by much thinner ice might precondition for rapid sea ice retreat in summer. Aim of the TIFAX campaign is to monitor ice conditions during summer in the main export pathway of the Arctic Ocean. The campaign complements the large scale spring sea ice surveys in April 2009 and 2011 (PAMARCMIP) and is a continuation of the TIFAX campaign in 2010. This document summarizes data and quality of the data taken on flight with the HEM-Bird, a laserscanner and a nadir looking camera system mounted on board the Polar 5

TIFAX 2010 Summer Campaign - Sea ice thickness measurements with Polar 5 from Station Nord and Svalbard

Transport of sea ice through Fram Strait affects the global climate through its influence on the thermohaline circulation. In recognition of its importance, the ice thickness distribution across Fram Strait and in the area north of Greenland was subject of the TIFAX 2010 field campaign. The ice thickness was investigated by means of an airborne electromagnetic (EM) system with a single-frequency of 4.08 kHz. The instrument was towed by a research aircraft (Polar 5) 15 meters above the ice surface. The method utilizes the contrast of electrical conductivity between sea water and sea ice to determine the distance to the ice-water interface. An additional laser altimeter yields the distance to the uppermost reflecting surface, hence ice thickness is obtained as the ice- plus snow thickness from the difference between the laser range and the EM derived distance. In this data report, all tracks/profiles taken during TIFAX 2010 are presented

TIFAX 2010 Summer Campaign - Sea ice thickness measurements with Polar 5 from Station Nord and Svalbard

Transport of sea ice through Fram Strait affects the global climate through its influence on the thermohaline circulation. In recognition of its importance, the ice thickness distribution across Fram Strait and in the area north of Greenland was subject of the TIFAX 2010 field campaign. The ice thickness was investigated by means of an airborne electromagnetic (EM) system with a single-frequency of 4.08 kHz. The instrument was towed by a research aircraft (Polar 5) 15 meters above the ice surface. The method utilizes the contrast of electrical conductivity between sea water and sea ice to determine the distance to the ice-water interface. An additional laser altimeter yields the distance to the uppermost reflecting surface, hence ice thickness is obtained as the ice- plus snow thickness from the difference between the laser range and the EM derived distance. In this data report, all tracks/profiles taken during TIFAX 2010 are presented

Remote sensing of aerosols in the Arctic for an evaluation of global climate model simulations

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are madeIn this study Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua retrievals of aerosol optical thickness (AOT) at 555 nm are compared to Sun photometer measurements from Svalbard for a period of 9 years. For the 642 daily coincident measurements that were obtained, MODIS AOT generally varies within the predicted uncertainty of the retrieval over ocean (ΔAOT=±0.03±0.05·AOT). The results from the remote sensing have been used to examine the accuracy in estimates of aerosol optical properties in the Arctic, generated by global climate models and from in situ measurements at the Zeppelin station, Svalbard. AOT simulated with the Norwegian Earth System Model/Community Atmosphere Model version 4 Oslo global climate model does not reproduce the observed seasonal variability of the Arctic aerosol. The model overestimates clear-sky AOT by nearly a factor of 2 for the background summer season, while tending to underestimate the values in the spring season. Furthermore, large differences in all-sky AOT of up to 1 order of magnitude are found for the Coupled Model Intercomparison Project phase 5 model ensemble for the spring and summer seasons. Large differences between satellite/ground-based remote sensing of AOT and AOT estimated from dry and humidified scattering coefficients are found for the subarctic marine boundary layer in summer.Peer reviewe

A Pan-Arctic Airborne Sea Ice Observation System

We present an Arctic sea-ice observation system that focuses on unique direct observations of sea ice plus snow thickness. A network of research institutions, the Alfred Wegener Institute, York University and the Norwegian Polar Institute, maintain an observation system that is embedded in several national and international projects and supported by research partners. Activities in the field include the use of long-range polar research aircraft and helicopter operations from research icebreakers and bases on land. Data collections are based on electromagnetic induction sounding and consistent time series are available in key regions of the Arctic Ocean since 2001. The increased use of polar research aircrafts in recent years has resulted in several initiatives that aim for long-term observations of ice thickness during seasonal minimum and maximum sea-ice extent in the Arctic. The scientific payload of the research aircraft of type Basler BT-67 and its capability to fly low-altitude surveys makes it an ideal tool for the validation and on-going verification of various satellite remote sensing products. The availability of airborne sea-ice thickness information spans the periods of different satellite sea-ice thickness retrieval concepts, such as the radar altimeters from Envisat and CryoSat-2 as well as the laser altimeter from ICESat-1 and -2. Wherever possible, the airborne surveys are accompanied by in-situ observations on the ice surface to compile a hierarchy of validation data from local to basin scales. Results of the observation network have found broad use for studying inter-annual variability and changes of sea ice thickness as well as the validation of satellite data products. We identify a gap of observations over the multi-year sea ice zone during the melt season and early freeze-up. We also stress the need for the continuation of a coordinated observational program that has produced a time series of sea ice thickness only paralleled by submarine observations. We plan to augment the observation system by simultaneous measurements of snow depth and to investigate opportunities for technological advances, such as the utilization of unmanned aerial systems

Where does the optically detectable aerosol in the European arctic come from?

In this paper, we pose the question where the source regions of the aerosol, which occurs in the European Arctic, are located. Long-term aerosol optical depth (AOD) data from Ny-Ålesund and Sodankylä as well as short-term data from a campaign on a Russian drifting station were analysed by air backtrajectories, analysis of the general circulation pattern and a correlation to chemical composition from in-situ measurements. Surprisingly, our data clearly shows that direct transport of pollutants from Europe does not play an important role. Instead, Arctic haze in Ny-Ålesund has been found for air masses from the Eastern Arctic, while events with increased AOD but chemically more diverse composition have been found for air from Siberia or the central Arctic. Moreover, the AOD in Ny-Ålesund does not depend on the North Atlantic Oscillation (NAO). Hence, either the pollution pathways of aerosol are more complex or aerosol is significantly altered by clouds

Combining atmospheric and snow radiative transfer models to assess the solar radiative effects of black carbon in the Arctic

The magnitude of solar radiative effects (cooling or warming) of black carbon (BC) particles embedded in the Arctic atmosphere and surface snow layer was explored on the basis of case studies. For this purpose, combined at- mospheric and snow radiative transfer simulations were per- formed for cloudless and cloudy conditions on the basis of BC mass concentrations measured in pristine early summer and more polluted early spring conditions. The area of inter- est is the remote sea-ice-covered Arctic Ocean in the vicin- ity of Spitsbergen, northern Greenland, and northern Alaska typically not affected by local pollution. To account for the radiative interactions between the black-carbon-containing snow surface layer and the atmosphere, an atmospheric and snow radiative transfer model were coupled iteratively. For pristine summer conditions (no atmospheric BC, minimum solar zenith angles of 55◦) and a representative BC particle mass concentration of 5 ng g−1 in the surface snow layer, a positive daily mean solar radiative forcing of +0.2Wm−2 was calculated for the surface radiative budget. A higher load of atmospheric BC representing early springtime conditions results in a slightly negative mean radiative forcing at the surface of about −0.05 W m−2, even when the low BC mass concentration measured in the pristine early summer condi- tions was embedded in the surface snow layer. The total net surface radiative forcing combining the effects of BC em- bedded in the atmosphere and in the snow layer strongly de- pends on the snow optical properties (snow specific surface area and snow density). For the conditions over the Arctic Ocean analyzed in the simulations, it was found that the at- mospheric heating rate by water vapor or clouds is 1 to 2 or-ders of magnitude larger than that by atmospheric BC. Sim- ilarly, the daily mean total heating rate (6 K d−1) within a snowpack due to absorption by the ice was more than 1 order of magnitude larger than that of atmospheric BC (0.2 K d−1). Also, it was shown that the cooling by atmospheric BC of the near-surface air and the warming effect by BC embedded in snow are reduced in the presence of clouds

Atmospheric concentrations of black carbon are substantially higher in spring than summer in the Arctic

A key driving factor behind rapid Arctic climate change is black carbon, the atmospheric aerosol that most efficiently absorbs sunlight. Our knowledge about black carbon in the Arctic is scarce, mainly limited to long-term measurements of a few ground stations and snap-shots by aircraft observations. Here, we combine observations from aircraft campaigns performed over nine years, and present vertically resolved average black carbon properties. A factor of four higher black carbon mass concentration (21.6 ng m$^{–3}$ average, 14.3 ng m$^{–3}$ median) was found in spring, compared to summer (4.7 ng m$^{–3}$ average, 3.9 ng m$^{–3}$ median). In spring, much higher inter-annual and geographic variability prevailed compared to the stable situation in summer. The shape of the black carbon size distributions remained constant between seasons with an average mass mean diameter of 202 nm in spring and 210 nm in summer. Comparison between observations and concentrations simulated by a global model shows notable discrepancies, highlighting the need for further model developments and intensified measurements