ABSTRACT This paper examines climatology of dust deposition events in the Caucasus Mountains, pre... more ABSTRACT This paper examines climatology of dust deposition events in the Caucasus Mountains, presents a multi-disciplinary set of techniques used for dating and provenancing dust deposition events, and compares the observations with simulations by HiGAM model. Samples of desert dust were obtained for 2009-2011 from snow pits and shallow ice cores at the Grabashi Glacier, Mt Elbrus (43°18'16.8''N, 42°27'48,4''E) at the altitudes between 3860 and 5000 m above sea level. Desert dust deposition was recorded 3-4 times a year, mostly between March and June. Analysis of SEVIRI satellite imagery and back trajectory data revealed two main source regions of desert dust deposited on Mt Elbrus: the Saharan foothills of the Akhdar Mountains in northern Libya and the Arabian Peninsula. Transportation of dust from North Africa is associated with the Saharan depressions migrating north-east along the Mediterranean coast and across Syria and Iraq. Transportation of dust from the Arabian peninsula is associated with the extensions of the Siberian anticyclone north-west of the Caspian Sea. Dust deposition at Mt Elbrus occurred when the dust-containing air masses mixed with precipitation-bearing frontal systems. Analysis of volumatic particle size distribution indicated that that silt dominates and revealed significant presence of fine sand. The obtained climatology of frequency and pathways of desert dust and particle size distributions were in good agreement with HiGAM simulations. From this study, we conclude that dust deposition events in the high-altitude region of the Caucasus occur as frequently as in the European Alps and that both timing and intensity of dust deposition events may have significant impact on glacier energy balance and enhance glacier melt.
ABSTRACT Dust aerosol transported to the high mountains and is deposited and stored in snow pack ... more ABSTRACT Dust aerosol transported to the high mountains and is deposited and stored in snow pack and glacier ice. Present and past records of dust stored in glaciers provide valuable information on frequency of deposition events, source regions and atmospheric pathways of mineral dust. The Caucasus Mountains, located between the Black and the Caspian seas is a glacierized region affected by deposition of desert dust from the Middle East and Sahara. In this study, a combination of ice core analysis, remote sensing and air mass trajectory modelling was used to identify the source regions of dust deposited on the glaciers of Mt Elbrus in the central Greater Caucasus and to characterize atmospheric pathways of dust with high temporal and spatial resolution. Shallow ice cores were extracted at Mt Elbrus in 2009 and 2012. Dust deposition events, recorded as brown layers in the snow, firn and ice were dated to the precision on months using oxygen and deuterium isotopic analyses. Examination of the local meteorological and NCEP/NCAR reanalysis data and application of HYSPLIT atmospheric trajectory model enabled dating dust deposition events with a precision of days, identification of potential source regions of desert dust and its pathways in the atmosphere. Examination of red-blue green infrared composite imagery from Spinning Enhanced Visible and Infra-Red Imager (SEVIRI) on board the Meteosat Second Generation (MSG) satellite enabled further provenancing of desert dust with high temporal (hours) and spatial (c. 100 km) resolution. Seventeen dust layers deposited between May 2009 and July 2012 were detected in the shallow cores. The source regions of the desert dust transported to Mt Elbrus were primarily located in the Middle East, in particular in eastern Syria and in the Syrian Desert at the border between Saudi Arabia, Iraq and Jordan. Northern Sahara, the foothills of the Djebel Akhdar Mountains in eastern Libya and the border region between Libya and Algeria were other important sources of desert dust. Fifteen dust deposition events occurred between March and June and two events occurred in October. The relatively high frequency of dust deposition events on Mt Elbrus may be due to the prolonged 2007-2010 drought in the Middle East resulting in more frequent activation of dust sources. Particle size and shape distributions were analysed for each dust sample using scanning electron microscope (SEM). The volume median diameter of dust particles from dust samples ranged from 3 to 13 microns. Particles with diameter of 1-10 microns accounted for 90±3% of the analysed samples. Detailed characterization of desert dust pathways from the Middle East and Sahara to the Caucasus leads to better understanding of pathways of desert dust in the atmosphere and highlights the importance of the Elbrus deep ice cores for the reconstruction of past environmental conditions in the south-eastern Europe and the Middle East in the future. This study is supported by the Marie Curie FP7-PEOPLE-2010-IIF project DIOGENES; Royal Soc JP100-235; RFBR N 1105-00304-a.
ABSTRACT This paper examines climatology of dust deposition events in the Caucasus Mountains, pre... more ABSTRACT This paper examines climatology of dust deposition events in the Caucasus Mountains, presents a multi-disciplinary set of techniques used for dating and provenancing dust deposition events, and compares the observations with simulations by HiGAM model. Samples of desert dust were obtained for 2009-2011 from snow pits and shallow ice cores at the Grabashi Glacier, Mt Elbrus (43°18'16.8''N, 42°27'48,4''E) at the altitudes between 3860 and 5000 m above sea level. Desert dust deposition was recorded 3-4 times a year, mostly between March and June. Analysis of SEVIRI satellite imagery and back trajectory data revealed two main source regions of desert dust deposited on Mt Elbrus: the Saharan foothills of the Akhdar Mountains in northern Libya and the Arabian Peninsula. Transportation of dust from North Africa is associated with the Saharan depressions migrating north-east along the Mediterranean coast and across Syria and Iraq. Transportation of dust from the Arabian peninsula is associated with the extensions of the Siberian anticyclone north-west of the Caspian Sea. Dust deposition at Mt Elbrus occurred when the dust-containing air masses mixed with precipitation-bearing frontal systems. Analysis of volumatic particle size distribution indicated that that silt dominates and revealed significant presence of fine sand. The obtained climatology of frequency and pathways of desert dust and particle size distributions were in good agreement with HiGAM simulations. From this study, we conclude that dust deposition events in the high-altitude region of the Caucasus occur as frequently as in the European Alps and that both timing and intensity of dust deposition events may have significant impact on glacier energy balance and enhance glacier melt.
ABSTRACT Dust aerosol transported to the high mountains and is deposited and stored in snow pack ... more ABSTRACT Dust aerosol transported to the high mountains and is deposited and stored in snow pack and glacier ice. Present and past records of dust stored in glaciers provide valuable information on frequency of deposition events, source regions and atmospheric pathways of mineral dust. The Caucasus Mountains, located between the Black and the Caspian seas is a glacierized region affected by deposition of desert dust from the Middle East and Sahara. In this study, a combination of ice core analysis, remote sensing and air mass trajectory modelling was used to identify the source regions of dust deposited on the glaciers of Mt Elbrus in the central Greater Caucasus and to characterize atmospheric pathways of dust with high temporal and spatial resolution. Shallow ice cores were extracted at Mt Elbrus in 2009 and 2012. Dust deposition events, recorded as brown layers in the snow, firn and ice were dated to the precision on months using oxygen and deuterium isotopic analyses. Examination of the local meteorological and NCEP/NCAR reanalysis data and application of HYSPLIT atmospheric trajectory model enabled dating dust deposition events with a precision of days, identification of potential source regions of desert dust and its pathways in the atmosphere. Examination of red-blue green infrared composite imagery from Spinning Enhanced Visible and Infra-Red Imager (SEVIRI) on board the Meteosat Second Generation (MSG) satellite enabled further provenancing of desert dust with high temporal (hours) and spatial (c. 100 km) resolution. Seventeen dust layers deposited between May 2009 and July 2012 were detected in the shallow cores. The source regions of the desert dust transported to Mt Elbrus were primarily located in the Middle East, in particular in eastern Syria and in the Syrian Desert at the border between Saudi Arabia, Iraq and Jordan. Northern Sahara, the foothills of the Djebel Akhdar Mountains in eastern Libya and the border region between Libya and Algeria were other important sources of desert dust. Fifteen dust deposition events occurred between March and June and two events occurred in October. The relatively high frequency of dust deposition events on Mt Elbrus may be due to the prolonged 2007-2010 drought in the Middle East resulting in more frequent activation of dust sources. Particle size and shape distributions were analysed for each dust sample using scanning electron microscope (SEM). The volume median diameter of dust particles from dust samples ranged from 3 to 13 microns. Particles with diameter of 1-10 microns accounted for 90±3% of the analysed samples. Detailed characterization of desert dust pathways from the Middle East and Sahara to the Caucasus leads to better understanding of pathways of desert dust in the atmosphere and highlights the importance of the Elbrus deep ice cores for the reconstruction of past environmental conditions in the south-eastern Europe and the Middle East in the future. This study is supported by the Marie Curie FP7-PEOPLE-2010-IIF project DIOGENES; Royal Soc JP100-235; RFBR N 1105-00304-a.
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Papers by Kevin White