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Dr. Lonnie Thompson
No full textProfessor Lonnie Thompson, School of Earth Science, Ohio State University & Byrd Polar Research Center speaks here in the 6th Northern Research Forum Open Assemly, held in Iceland in September 2011.
The sessions title is: Implications of the Ice Melt: A Global Overview.
please click on the link above to see the video
”New” POPs in marine mammals in Nordic Arctic and NE Atlantic areas during three decades
Get PDFThe report describes the findings of a Nordic study aiming to depict possible trends in “new” contaminants in marine mammals in Nordic Arctic waters over three decennia. The “new” contaminants in focus are the brominated flame retardants, BFRs, methoxylated PBDEs, perfluorinated
compounds including the PFOS family, and polychlorinated naphthalenes, PCNs. In addition, brominated dioxins and dibenzofurans were analysed in a subset of the samples.
The study aims at giving a wide scope of the presence of a selection of these “new” contaminants in marine mammals in recent time and so far back as is possible with extracting samples from specimen banks. The marine mammal species analysed were fin whale, minke whale, pilot whale, white-sided dolphins, harbour porpoise, ringed seal and hooded seal.
The study is the result of collaboration between Norway, Denmark/Greenland, Faroe Island, Iceland and Sweden. The funding for large parts of the project has been made available by the Nordic Council of Ministers via the working group on Akvatiska Ekosystemer
Distributions of dissolved inorganic carbon and total alkalinity in the Western Arctic Ocean
Get PDFThe third Chinese National Arctic Research Expedition (3rd CHINARE-Arctic in 2008) was carried out from July to September 2008. During the survey, numerous sea water samples were taken for CO2 parameter measurement (including total alkalinity TA and total dissolved inorganic carbon DIC).The distribution of CO2 parameters in the Western Arctic Ocean was determined, and the controlling factors are addressed. The ranges of summertime TA, normalized TA (nTA), DIC and normalized DIC (nDIC) in the surface seawater were 1.757 - 2.229 μmol * kg(-1), 2.383 - 2.722 μmol * kg(-1), 1.681 - 2.034 μmol * kg(-1), 2.119 - 2.600 μmol * kg(-1), respectively. Because of dilution from ice meltwater, the surface TA and DIC concentrations were relatively low. TA in the upper 100 m to the south of 78±N had good correlation with salinity, showing a conservative behavior. The distribution followed the seawater-river mixing line at salinity >30, then followed the seawater mixing line (diluted by river water to salinity = 30) with the ice meltwater. The DIC distribution in the Chukchi Sea was dominated by biological production or respiration of organic matter, whereas conservative mixing dominated the mixed layer TA distribution in the ice-free Canada Basin
Impacts of snow accumulation on air temperature measured by automatic weather stations on the Antarctic ice sheet
Get PDFThe heights of automatic weather station (AWS) sensors over the Antarctic ice sheet are nominal and change with snow accumulation or ablation. Therefore, the measured data may not be used directly. In this study, we analyzed the impact of snow accumulation on AWS observations using continuous measurements from three AWS that were deployed on the traverse route from the Zhongshan Station to Dome A over East Antarctica. We then corrected the measured air temperature to account for changes in the sensor height relative to the snow surface to improve the authenticity and representativeness of the observation data from the AWS. The results show that (i) the annual mean snow accumulations at Dome A, Eagle and LGB69 were approximately 0.11 m, 0.30 m and 0.49 m, respectively, and the corresponding annual mean air temperature differences between the corrected and measured values at 1 m in height were 0.34℃, 0.29℃ and 0.35℃; (ii) the impact on air temperature from accumulation decreases with height from the surface; (iii) the air temperature difference between the corrected and measured values was not directly proportional to the snow accumulation but was related to the seasonal air temperature variations and the intensity of the local surface inversion; and (iv) the averaged corrected air temperature was higher than the measured values except during the summer when there were days without temperature inversion. The magnitude of the temperature difference between the corrected and measured was mainly determined by snow accumulation and the intensity of the local surface inversion
Investigation of the thermodynamic processes of a floe-lead system in the central Arctic during later summer
Get PDFThermodynamic processes of a system involving a floe and a small lead in the central Arctic were investigated during the ice-camp period of the third Chinese National Arctic Research Expedition from 20 to 28 August, 2008. The measurements included surface air temperatures above the floe, spectral albedo of the lead, seawater temperatures in the lead and under the ice cover, and the lateral and bottom mass balance of the floe. The surface air temperature at 1.15 m remained below 0℃ throughout the observation period and sea ice had commenced its annual cycle of growth in response to autumn cooling during the study. The surface of the lead was frozen by 23 August, after which the spectral albedo of the thin-ice-covered lead in the band of 320−950 nm was 0.46 ±0.03, the seawater temperatures both in the lead and under the ice cover, as well as the vertical seawater-temperature gradient in the lead decreased gradually, and the oceanic heat under the ice was maintained at a low level approaching 0 W/m2. By the end of the measurement, the thickness of the investigated floe had reached its annual minimum, while the lateral of the floe was still in the melting phase, with a mean melting rate of 1.0 ±0.3 cm/d during the measurement, responding to an equivalent latent heat flux of 21 ±6 W/m2. The lateral melting of the floe had made a more significant contribution to the sea-ice mass balance than the surface and bottom melting in the end of August
Cloning and heterologous expression of pro-2127, a gene encoding cold-active protease from Pseudoalteromonas sp. QI-1
Get PDFThe psychrotropic bacterium, Pseudoalteromonas sp. QI-1, which produces extracellular cold-active protease, was isolated from Antarctic seawater. The genomic DNA of this bacterium was used to construct a plasmid genomic library with the goal of screening cold-active protease genes. Gene pro-2127 with an open reading frame of 2127 bp encoding protease PRO-2127 was cloned and sequenced. Alignment of amino acid sequences suggested that the precursor of PRO-2127 was a member of subfamily S8A, and that it might contain four domains: a signal peptide, an N-terminal prosequence, a catalytic domain and a C-terminal extension. Amino acids Asp185, His244 and Ser425 might form a catalytic triad. PRO-2127 showed some structural features common to psychrophilic enzymes, such as a decrease in Arg residues and the Arg/(Arg+Lys) ratio. Heterologous expression of pro-2127 in Escherichia coli BL21 (DE3) by pColdIII was also successfully observed in this study
Potential application of biogenic silica as an indicator of paleo-primary productivity in East Antarctic lakes
Get PDFWe collected two lake sediment cores (MC and DM) from the East Antarctic region for analysis of biogenic silica and other biogeochemical parameters (e.g., organic matter, C, N, S, H). Based on synthetically comparative research, we focused on the potential application of biogenic silica (BSi) for the reconstruction of paleo-primary productivity in the East Antarctic lakes. Analytical results showed that a large number of diatoms were well preserved in the freshwater lake sediments, and that concentrations of biogenic silica displayed notable fluctuations over different water depths. The content of biogenic silica had a consistent profile over water depth, and this pattern changed with organic matter, reflecting their potential as eco-environmental proxies. Low levels of BSi and organic matter indicated reduction of lake algal production, and corresponded to decreased lake primary productivity. Due to the fragile ecosystem state and limited contribution of terrestrial organic matter in the East Antarctic lakes, the contents of biogenic silica in the lacustrine sediments can sensitively indicate the evolutionary history of paleo primary productivity. Overall, BSi is an ideal proxy for the reconstruction of past eco-environmental change recorded in the lacustrine sediments on East Antarctica
Summer water temperature structures and their interannual variation in the upper Canada Basin
Get PDFConductivity, temperature and depth (CTD) data from 1993{2010 are used to study water temperature in the upper Canada Basin. There are four kinds of water temperature structures: The remains of the winter convective mixed layer, the near-surface temperature maximum (NSTM), the wind-driven mixed layer, and the advected water under sea ice. The NSTM mainly appears within the conductive mixed layer that forms in winter.
Solar heating and surface cooling are two basic factors in the formation of the NSTM. The NSTM can also appear in undisturbed open water, as long as there is surface cooling. Water in open water areas may advect beneath the sea ice. The overlying sea ice cools the surface of the advected water, and a temperature maximum could appear similar to the NSTM. The NSTM mostly occurred at depths 10{30 m because of its deepening and strengthening during summer, with highest frequency at 20 m. Two clear stages of interannual variation are identified. Before 2003, most NSTMs were observed in marginal ice zones and open waters, so temperature maxima were usually warmer than 0°C. After 2004, most NSTMs occurred in ice-covered areas, with much colder temperature maxima. Average depths of the temperature maxima in most years were about 20 m, except for about 16 m in 2007, which was related to the extreme minimum of ice cover. Average temperatures were around {0.8°C to {1.1°C, but increased to around {0.5°C in 2004, 2007 and 2009, corresponding to reduced sea ice. As a no-ice summer in the Arctic is expected, the NSTM will be warmer with sea ice decline. Most energy absorbed by seawater has been transported to sea ice and the atmosphere. The heat near the NSTM is only the remains of total absorption, and the energy stored in the NSTM is not considerable. However, the NSTM is an important sign of the increasing absorption of solar energy in seawater
The Northern Research Forum, a case study for High Northern cooperation.
No full textMargret Cela, University of Lapland, Finland / Iceland, at the NRF 6th open Assembly in Hveragerði, Iceland. September 2011