Search results for "Arctic ice pack"

Ion fractionation in young sea ice from Kongsfjorden, Svalbard

2011

AbstractThe fractionation of major sea-water ions, or deviation in their relative concentrations from Standard Mean Ocean Water ratios, has been frequently observed in sea ice. It is generally thought to be associated with precipitation of solid salts at certain eutectic temperatures. the variability found in bulk sea-ice samples indicates that the fractionation of ions depends on the often unknown thermal history of sea ice, which affects the structure of pore networks and fate of solid salts within them. Here we investigate the distribution of ions in Arctic sea ice that is a few weeks old with a reconstructible thermal history. We separate the centrifugable (interconnected) and entrapped…

Higher sensitivity towards light stress and ocean acidification in an Arctic sea-ice-associated diatom compared to a pelagic diatom.

2020

Thalassiosira hyalina and Nitzschia frigida are important members of Arctic pelagic and sympagic (sea-ice-associated) diatom communities. We investigated the effects of light stress (shift from 20 to 380 µmol photons m-2  s-1 , resembling upwelling or ice break-up) under contemporary and future pCO2 (400 vs 1000 µatm). The responses in growth, elemental composition, pigmentation and photophysiology were followed over 120 h and are discussed together with underlying gene expression patterns. Stress response and subsequent re-acclimation were efficiently facilitated by T. hyalina, which showed only moderate changes in photophysiology and elemental composition, and thrived under high light aft…

Arctic sea ice algae differ markedly from phytoplankton in their ecophysiological characteristics

2021

Photophysiological and biochemical characteristics were investigated in natural communities of Arctic sea ice algae and phytoplankton to understand their respective responses towards variable irradiance and nutrient regimes. This study revealed large differences in photosynthetic efficiency and capacity between the 2 types of algal assemblages. Sea ice algal assemblages clearly displayed increased photoprotective energy dissipation under the highest daily average irradiance levels (>8 µmol photons m-2 s-1). In contrast, phytoplankton assemblages were generally light-limited within the same irradiance ranges. Furthermore, phytoplankton assemblages exhibited more efficient carbon assimilat…

Microphysical and radiative characterization of a subvisible midlevel Arctic ice cluod by airborne observations - a case study

2009

During the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) campaign, which was conducted in March and April 2007, an optically thin ice cloud was observed south of Svalbard at around 3 km altitude. The microphysical and radiative properties of this particular subvisible midlevel cloud were investigated with complementary remote sensing and in situ instruments. Collocated airborne lidar remote sensing and spectral solar radiation measurements were performed at a flight altitude of 2300 m below the cloud base. Under almost stationary atmospheric conditions, the same subvisible midlevel cloud was probed with various in situ sensors roughly 30 min later. <br><br> …

2018

Abstract. Low planetary wave activity led to a stable vortex with exceptionally cold temperatures in the 2015–2016 Arctic winter. Extended areas with temperatures below the ice frost point temperature Tice persisted over weeks in the Arctic stratosphere as derived from the 36-year temperature climatology of the ERA-Interim reanalysis data set of the European Centre for Medium-Range Weather Forecasts (ECMWF). These extreme conditions promoted the formation of widespread polar stratospheric ice clouds (ice PSCs). The space-borne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument on board the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) satellit…

Sea ice extent and seasonality for the Early Pliocene northern Weddell Sea

2010

Abstract Growth increment analysis coupled with stable isotopic data ( δ 18 O/ δ 13 C) from Early Pliocene (ca 4.7 Ma) Austrochlamys anderssoni from shallow marine sediments of the Cockburn Island Formation, northern Antarctic Peninsula, suggest these bivalves grew through much of the year, even during the coldest parts of winter recorded in the shells. The high frequency fluctuation in growth increment width of A. anderssoni appears to reflect periodic, but year-round, agitation of the water column enhancing benthic food supply from organic detritus. This suggests that Austrochlamys favoured waters that were largely sea ice free. Our data support interpretation of the Cockburn Island Forma…

Recent Change—River Run-off and Ice Cover

2015

This chapter compiles and assesses information on run-off and discharge from rivers within the Baltic Sea drainage basin. Some information is also available on ice duration on inland waterways. Although decadal and regional variability is large, no significant long-term change has been detected in total river run-off to the Baltic Sea over the past 500 years. A change in the timing of the spring flood has been observed due to changes in the timing of snowmelt . Change in temperature seems to explain change in run-off better than does precipitation. Later start dates for ice formation on waterways, and earlier ice break-up dates have resulted in shorter periods of ice cover.

Widespread persistent polar stratospheric ice clouds in the Arctic

2016

Abstract. Despite a general decline in ozone depleting substances in the stratosphere due to the multi-national commitment to substantially reduce the emissions of their precursors, the magnitude of Arctic polar ozone loss has not decreased in recent years. Thus new observations at cold conditions can help to enhance our knowledge of polar stratospheric cloud (PSC) formation and life cycle which is of relevance for Arctic ozone loss. In the unique winter 2015/16, cold and persistent areas with temperatures below the ice frost point Tice developed in the Arctic stratosphere, caused by reduced perturbations of the polar vortex through planetary waves. Due to these extreme conditions, unpreced…

Recent Change—Atmosphere

2015

This chapter examines past and present studies of variability and changes in atmospheric variables within the North Sea region over the instrumental period; roughly the past 200 years. The variables addressed are large-scale circulation, pressure and wind, surface air temperature, precipitation and radiative properties (clouds, solar radiation, and sunshine duration). Temperature has increased everywhere in the North Sea region, especially in spring and in the north. Precipitation has increased in the north and decreased in the south. There has been a north-eastward shift in storm tracks, which agrees with climate model projections. Due to large internal variability, it is not clear which a…