Annual cycle of the active surface layer in Western Dronning Maud Land, Antarctica

Antarctica is a major component in the climate system of the earth, acting as a large heat sink in the energy balance. The climatic conditions of Antarctica maintain the snow and ice cover that blankets almost completely the surface area of the continent. Physical properties of snow readily respond to changing environmental conditions and remote sensing signals are sensitive to these properties. The annual changes in the physical properties of the snow cover, especially in the coastal area, must be taken into account when snow cover and climate models are produced. In situ observations are needed for calibration and validation of these models. The aim of the present study was to examine the annual cycle of the active 10-m surface layer in western Dronning Maud Land, Antarctica. The data were collected along a 300-km-long transect from the coast to the edge of the high plateau during the field campaigns in austral summers 2004-2005, 2009-2010 and 2010-2011 as a part of the Finnish Antarctic Research Programme (FINNARP). The studies were focused on the uppermost part of the ice sheet covering the most recent annual accumulation in the coastal area. The results showed that the present study lakes froze completely during winter and showed similar evolution but the exact timing depended on the location. In January, the general structure of lake Suvivesi was following: two layers, each about 1 m thick, an upper layer with a thin ice layer on top and main body of liquid water, and a lower layer containing slush and hard ice sub-layers. The formation and the depth scale of the present study lakes are determined by the light extinction distance and thermal diffusion coefficient, limiting the growth to less than ~1.5 m in one summer. In Antarctica, the mean spectral diffuse extinction coefficient varied between 0.04 and 0.31 cm-1 (10-20-cm snow layer) and varied only slightly between locations when the grain type was the same. The theoretically calculated average depth where broadband irradiance (400-700-nm band) was 1 % of the downwelling irradiance at the surface, was 50 cm. On the continental ice sheet, the compaction rate of the snowpack was 0.0201 ± 0.02 y-1 and the power spectra revealed a daily cycle, synoptic scale variability (~10 days), and variability in a low-frequency band of 60-120 days at a depth of 54 cm. The investigations of snow patches in Basen nunatak revealed that much more snow was lost in summer 2010-2011 (6.3 mm d-1 water equivalent (w.e.)) than in 2004-2005 (4 mm d-1 w.e.).Etelämantereen pinta-alasta 98 % on lumen ja jään peitossa ja parhaimmillaan lumi heijastaa jopa 90 % tulevasta auringon säteilystä takaisin avaruuteen. Lumen suuren heijastuskyvyn takia Etelämantereella on suuri vaikutus maapallon ilmastoon toimien valtavana lämpönieluna . Lumen heijastuskyky on riippuvainen lumen fysikaalisista ominaisuuksista (mm. kidekoko ja muoto sekä märkyys) ja nämä ominaisuudet reagoivat herkästi muutoksiin valitsevissa meteorologisissa olosuhteissa. Etenkin satelliittikaukokartoituksessa käytetyt signaalit ovat herkkiä lumessa tapahtuville muutoksille. Vuotuinen sykli rannikkoalueen pintalumen fysikaalisissa ominaisuuksissa on otettava huomioon matemaattisissa lumi- ja ilmastomalleissa. Tämän väitöskirjan päätavoitteena oli kartoittaa Etelämantereen jäätikön pintakerroksen vuotuinen sykli rannikkoalueella. Tutkimuskohteina oli 10 m paksu pintalumikerros sekä kolme sinisen jään aluetta, jonne muodostuu kesäkausina sulavesijärviä. Sinisen jään alue on vapaana lumesta ja näkyvissä ympäri vuoden voimakkaiden tuulien takia. Tutkimukset suoritettiin Etelämantereen kesäkausien 2004-2005, 2009-2010 ja 2010-2011 aikana läntisellä Kuningatar Maudin maalla. Suomen Aboa-tutkimusasema toimi tukikohtana kenttämittausten ajan sisältäen 300 km pitkän mittauslinjan rannikolta sisämaahan pinnankorkeuden vaihdellessa 30 m ja 2000 m välillä. Lumen fysikaalisia ominaisuuksia (tiheys, kovuus, märkyys, kidekoko ja muoto ja kerrosrakenne) havainnointiin 1,5 m syvistä lumikuopista sekä tutkimalla miten valo vaimenee lumen sisällä. Lisäksi lumen lämpötilan seuraamiseksi eri syvyyksillä lumeen asennettiin kaksi ympärivuotista automaattisista mitta-asemaa. Sulavesijärvien kehitys sinisen jään alueilla saatiin selville veden virtauskokeiden, jäänäytekairauksien ja säteilymittausten avulla. Tulokset osoittavat, että nykyilmastossa sinisen jään alueiden sulavesijärvet ovat yksivuotisia eli jäätyvät kokonaan umpeen talvikauden aikana. Sulavesijärven rakenteen kehitys oli kaikkialla samanlainen, mutta ajallinen kehitys oli riippuvainen sijainnista. Valo-mittaukset osoittivat, että lumessa 50 cm syvyydellä valon voimakkuus on vaimentunut yhteen prosenttiin sekä tukevan tietoa, että lumi on rakenteeltaan hyvin samankaltaista kaikkialla muutamaa poikkeusta lukuun ottamatta. Nykyilmastossa havaittuja lumen lämpötilasyklejä voidaan käyttää vertailukohteena tulevaisuudessa suoritettaville mittauksille. Lisäksi tulokset osoittivat pintalumikerroksen käyttäytyvän erilailla rannikon tuntumassa (pinnankorkeus alle 100 m) kuin sisämaassa (pinnankorkeus yli 300 m)

Evolution of snow cover and dynamics of atmospheric deposits in the snow in the Antarctica. Data report

Field programme on the surface layer of the ice sheet in the Dronning Maud Land, Antarctica has been performed in 2009-2011. The objectives were to examine the annual accumulation and sublimation history, snow melting, chemistry of snow impurities, and life history of supraglacial and epiglacial lakes in blue ice regions. Fieldwork was done during FINNARP 2009 and 2010 expeditions. The sites were at the Finnish research station Aboa (73 02.5'S, 013 24.4'W), a snow line from Rampen at the edge of the ice shelf pass Aboa to the station Svea, and blue ice at Basen and neighboring nunataks. Snow measurements were made using classical snow pit method, ice and snow sampling, and with automatic observation stations (surface radiation balance, penetration of sunlight into snow and ice, and temperature within the surface layer of snow and ice). Life history, physics, and ecological state of lakes were mapped. This document is the data report including a brief project introduction, descriptions of the experiments, and the data obtained

Interannual variability and trends in winter weather and snow conditions in Finnish Lapland

The interannual variability of the air temperature, precipitation and snow conditions were examined in the Finnish Arctic region based on data from the period 1946-2012. The purpose of this work was to describe the climatology of the region and to examine long-term variations in the climatic parameters. This information is essential for both environmental and socioeconomic aspects of the Finnish Arctic region. The air temperature, precipitation and snow depth records from nine weather stations were analysed in order to study the evolution of the winter duration (sub-zero temperature days), precipitation, snow cover duration and snow depth. The climatological description was based on the most recent 30-year period record available (1982-2011). Since 1946, air temperature has increased significantly by 0.4 degrees C/decade. Significant precipitation trends reached up to 35 mm/decade. For the most part there were no significant trends in snow depth and snow cover duration.Peer reviewe

Phosphate Binding with Sevelamer Preserves Mechanical Competence of Bone Despite Acidosis in Advanced Experimental Renal Insufficiency

Introduction Phosphate binding with sevelamer can ameliorate detrimental histomorphometric changes of bone in chronic renal insufficiency (CRI). Here we explored the effects of sevelamer-HCl treatment on bone strength and structure in experimental CRI. Methods Forty-eight 8-week-old rats were assigned to surgical 5/6 nephrectomy (CRI) or renal decapsulation (Sham). After 14 weeks of disease progression, the rats were allocated to untreated and sevelamer-treated (3% in chow) groups for 9 weeks. Then the animals were sacrificed, plasma samples collected, and femora excised for structural analysis (biomechanical testing, quantitative computed tomography). Results Sevelamer-HCl significantly reduced blood pH, and final creatinine clearance in the CRI groups ranged 30%-50% of that in the Sham group. Final plasma phosphate increased 2.4- to 2.9-fold, and parathyroid hormone 13- to 21-fold in CRI rats, with no difference between sevelamer-treated and untreated animals. In the femoral midshaft, CRI reduced cortical bone mineral density (-3%) and breaking load (-15%) (p Conclusions In this model of stage 3-4 CRI, sevelamer-HCl treatment ameliorated the decreases in femoral midshaft and neck mineral density, and restored bone strength despite prevailing acidosis. Therefore, treatment with sevelamer can efficiently preserve mechanical competence of bone in CRI.Peer reviewe

Hydroxysteroid 17-beta dehydrogenase 13 variant increases phospholipids and protects against fibrosis in nonalcoholic fatty liver disease

Carriers of the hydroxysteroid 17-beta dehydrogenase 13 (HSD17B13) gene variant (rs72613567:TA) have a reduced risk of NASH and cirrhosis but not steatosis. We determined its effect on liver histology, lipidome, and transcriptome using ultra performance liquid chromatography-mass spectrometry and RNA-seq. In carriers and noncarriers of the gene variant, we also measured pathways of hepatic fatty acids (de novo lipogenesis [ONLI and adipose tissue lipolysis [ATL] using (H2O)-H-2 and H-2-glycerol) and insulin sensitivity using H-3-glucose and euglycemic-hyperinsulinemic clamp) and plasma cytokines. Carriers and noncarriers had similar age, sex and BMI. Fibrosis was significantly less frequent while phospholipids, but not other lipids, were enriched in the liver in carriers compared with noncarriers. Expression of 274 genes was altered in carriers compared with noncarriers, consisting predominantly of downregulated inflammation-related gene sets. Plasma IL-6 concentrations were lower, but DNL, ATL and hepatic insulin sensitivity were similar between the groups. In conclusion, carriers of the HSD17B13 variant have decreased fibrosis and expression of inflammation-related genes but increased phospholipids in the liver. These changes are not secondary to steatosis, ONL, ATL, or hepatic insulin sensitivity. The increase in phospholipids and decrease in fibrosis are opposite to features of choline-deficient models of liver disease and suggest HSD17B13 as an attractive therapeutic target.Peer reviewe

Soot-doped natural snow and its albedo — results from field experiments

Soot has a pronounced effect on the cryosphere and experiments are still needed to reduce the associated uncertainties. This work presents a series of experiments to address this issue, with soot being deposited onto a natural snow surface after which the albedo changes were monitored. The albedo reduction was the most pronounced for the snow with higher soot content, and it was observed immediately following soot deposition. Compared with a previous laboratory study the effects of soot on the snow were not as prominent in outdoor conditions. During snowmelt, about 50% of the originally deposited soot particles were observed to remain at the snow surface. More detailed experiments are however needed to better explain soot's effect on snow and to better quantify this effect. Our albedo versus soot parameterization agreed relatively well with previously published relationships.Peer reviewe