Search results for "RCT"

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…

Wintertime Airborne Measurements of Ice Nucleating Particles in the High Arctic: A Hint to a Marine, Biogenic Source for Ice Nucleating Particles

2020

Ice nucleating particles (INPs) affect the radiative properties of cold clouds. Knowledge concerning their concentration above ground level and their potential sources is scarce. Here we present the first highly temperature resolved ice nucleation spectra of airborne samples from an aircraft campaign during late winter in 2018. Most INP spectra featured low concentration levels (<3 · 10−4 L−1 at −15°C). −2 −1 However, we also found INP concentrations of up to 1.8·10 L at −15°C and freezing onsets as high as −7.5°C for samples mainly from the marine boundary layer. Shape and onset temperature of the ice nucleation spectra of those samples as well as heat sensitivity hint at biogenic INP. Col…

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…

Tectonothermal Evolution of the Broadly Rifted Zone, Ethiopian Rift

2019

The Broadly Rifted Zone (BRZ) of southern Ethiopia is a long-lived and structurally complex segment of the East African Rift System. However, due to poor surface exposure of early synrift strata and a dearth of subsurface data, the evolution of the BRZ remains poorly understood. We present new apatite (U-Th-Sm)/He and augmented apatite fission track low-temperature thermochronology data from the Beto and Galana basin boundary fault systems to constrain the tectonothermal evolution of the western and eastern BRZ, respectively. Time-temperature reconstructions suggest that East African Rift System-related extension began concurrently across the BRZ in the early Miocene (20–17 Ma), at least 6 …

Controls on modern carbonate sedimentation on warm-temperate to arctic coasts, shelves and seamounts in the Northern Hemisphere: Implications for fos…

1995

In contrast to the well studied tropical carbonate environments, interest in non-tropical carbonate deposition was rather low until the basic ideas of theForamol-concept were outlined byLees & Buller (1972). In the following two decades studies on non-tropical carbonate settings evolved as a new and exciting branch of carbonate sedimentology (seeNelson 1988). This is archieved in a great number of publications dealing on temperate carbonate deposits from numerous coastal and open shelf settings on both hemispheres. The existence of wide extended carbonate depositional systems and even reefal frameworks in Subarctic and Arctic seas which are in focus by our research group made it possible to…

Vertical profile of atmospheric dimethyl sulfide in the Arctic Spring and Summer

2017

Abstract. Vertical distributions of atmospheric dimethyl sulfide (DMS(g)) were sampled aboard the research aircraft Polar 6 near Lancaster Sound, Nunavut, Canada in July 2014 and on pan-Arctic flights in April 2015 that started from Longyearbyen, Spitzbergen, and passed through Alert and Eureka, Nunavut and Inuvik, Northwest Territories. Larger mean DMS(g) mixing ratios were present during April 2015 (campaign-mean of 116±8 pptv) compared to July 2014 (campaign-mean of 20±6 pptv). Observations in July 2014 indicated a decrease in DMS(g) mixing ratios with altitude up to about 3 km, and the largest mixing ratios were found near the surface above ice-edge and open water, coincident with incre…

Using a small COTS UAV to quantify moraine dynamics in Arctic environments

2016

International audience; Arctic regions are known to be places where climate shift yields most visible consequences. In this context, glaciers and their environment are highly subject to global warming effects. New dynamics are observed and the behaviour of arctic systems (such as glaciers, moraines, beaches etc) changes at rates visible over yearly observations. According to recent works on climate change impacts on the cryosphere, short/violent events are recently observed and are one characteristic of these changes. As a consequence, an accelerating rate of glacial and pro-glacial activity is observed, especially at the end of each hydrological season (early fall). As an example, many pha…

L'Arctique en mutation

2016

International audience; AVANT-PROPOS..........................................Daniel JOLYCHAPITRE 1 - Fluctuations climatiques récentes en Arctique : l’exemple du Spitsberg occidental, Madeleine GRISELIN, Christelle MARLIN et Jean-Michel FRIEDTCHAPITRE II - Évolution contemporaine des glaciers arctiques ; exemple de l’Austre Lovénbreen (79°N), Eric BERNARD et Florian TOLLECHAPITRE III - Géomorphologie des côtes rocheuses arctiques, SAMUEL ETIENNE, Jim HANSOM et Donald L. FORBESCHAPITRE IV - L’Arctique face aux crises géomorphologiques paraglaciaires, Denis MERCIERCHAPITRE V - Distribution multi-scalaire de la végétation en Arctique, Martha RAYNOLDCHAPITRE VI - Distribution de la végétation …

Carbon control of bacterioplankton in subarctic lakes and ponds

2015

Statistical upscaling of ecosystem CO2 fluxes across the terrestrial tundra and boreal domain: Regional patterns and uncertainties

2021

The regional variability in tundra and boreal carbon dioxide (CO2) fluxes can be high, complicating efforts to quantify sink-source patterns across the entire region. Statistical models are increasingly used to predict (i.e., upscale) CO2 fluxes across large spatial domains, but the reliability of different modeling techniques, each with different specifications and assumptions, has not been assessed in detail. Here, we compile eddy covariance and chamber measurements of annual and growing season CO2 fluxes of gross primary productivity (GPP), ecosystem respiration (ER), and net ecosystem exchange (NEE) during 1990–2015 from 148 terrestrial high-latitude (i.e., tundra and boreal) sites to a…