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1

Carbonyl sulfide (COS) measurements in the Arctic polar vortex  

Microsoft Academic Search

One stratospheric carbonyl sulfide (COS) vertical profile in the Arctic polar vortex has been retrieved from air samples collected by the MPAE balloon-borne cryogenic sampler on January 18, 1992, at Kiruna, Sweden. The measurements were made in the altitude range 7.5-28.5 km. The upper tropospheric volume mixing ratios of COS were 355+\\/-60 pptv. The stratospheric profile shows that COS is

K. A. Kourtidis; R. Borchers; P. Fabian; J. Harnisch

1995-01-01

2

A Cold Jovian Arctic Polar Vortex: Evidence from Infrared Imaging  

NASA Astrophysics Data System (ADS)

A prominent cold arctic airmass in Jupiter is revealed by thermal images taken at NASA's Infrared Telescope Facility (IRTF) during Jupiter's northern summer in 1999. This cold airmass is well defined by a sharp 4-degree thermal gradient in both the stratosphere and the upper troposphere and tropopause regions. The latitude boundary of the cold airmass oscillates in longitude with principal wavenumber 5--6. This longitudinal oscillation is coincident with the oscillation of the boundary of the thick polar hood that is detectable in reflected sunlight that is sensitive to particles around Jupiter's tropopause (~100 mbar pressure), using IRTF 2.3-?m and HST WFPC2 890-nm images. The sinusoidal boundaries slowly rotate prograde with respect to the interior. The proximity and similarity of the thermal and particle boundaries suggests that the phenomenon is a classical polar vortex of the same type as seen in the Earth's antarctic. Testing of possible gaseous entrainment within the vortex' area would verify or refute similarities with polar vortices in the Earth, Venus, Mars and possibly Titan. This phenomenon is relevant to studies of terrestrial meteorology by measuring the extent to which stratospheric phenomena can drive tropospheric properties. Detailed studies of Jupiter's polar regions might be most easily accomplished from appropriate remote sensing instrumentation on a polar orbiter mission as a result of optimized spatial resolution. The work reported here was supported by funds from NASA to the Jet Propulsion Laboratory, California Institute of Technology. Ori Fox was supported by the Undergraduate Student Researcher Program (USRP).

Orton, G. S.; Fisher, B. M.; Baines, K. H.; Momary, T.; Fox, O.

2002-12-01

3

Stratospheric Meteorological Conditions in the Arctic Polar Vortex, 1991 to 1992  

Microsoft Academic Search

Stratospheric meteorological conditions during the Airborne Arctic Stratospheric Expedition II (AASE II) presented excellent observational opportunities from Bangor, Maine, because the polar vortex was located over southeastern Canada for significant periods during the 1991-1992 winter. Temperature analyses showed that nitric acid trihydrates (NAT temperatures below 195 k) should have formed over small regions in early December. The temperatures in the

P. Newman; L. R. Lait; M. Schoeberl; E. R. Nash; K. Kelly; D. W. Fahey; R. Nagatani; D. Toohey; L. Avallone; J. Anderson

1993-01-01

4

Stratospheric meterological conditions in the Arctic polar vortex, 1991 to 1992  

SciTech Connect

Stratospheric meterological conditions during the Airborne Arctic Stratospheric Expedition II (AASE II) presented excellent observational opportunities from Bangor, Maine, because the polar vortex was located over southeastern Canada for significant periods during the 1991-1992 winter. Temperature analyses showed that nitric acid trihydrates (NAT temperatures below 195 k) should have formed over small regions in early December. The temperatures in the polar vortex warmed beyond NAT temperatures by late January (earlier than normal). Perturbed chemistry was found to be associated with these cold temperatures.

Newman, P.; Lait, L.R.; Schoeberl, M. (National Aeronautics and Space Administration, Greenbelt, MD (United States)); Nash, E.R. (Applied Research Corp., Landover, MD (United States)); Kelly, K.; Fahey, D.W. (National Oceanic and Atmospheric Administration, Boulder, CO (United States)); Nagatani, R. (National Meteorological Center, Washington, DC (United States)); Toohey, D.; Avallone, L. (Univ. of California, Irvine, CA (United States)); Anderson, J. (Harvard Univ., Cambridge, MA (United States))

1993-08-27

5

Aircraft Emissions Deposited in the Stratosphere and Within the Arctic Polar Vortex. Final report  

SciTech Connect

This report describes an analysis of the quantity of emissions (water vapor, NO(x)) projected to be deposited directly within the Arctic polar vortex by projected fleets of Mach 2.4 high speed civil transports (HSCT`s). It also evaluates the amount of emissions from subsonic aircraft which are emitted into the lower stratosphere using aircraft emission inventories developed earlier for May 1990 as representative of the annual average.

Baughcum, S.L.

1996-04-01

6

Stratospheric water vapour in the vicinity of the Arctic polar vortex  

NASA Astrophysics Data System (ADS)

The stratospheric water vapour mixing ratio inside, outside, and at the edge of the polar vortex has been accurately measured by the FLASH-B Lyman-Alpha hygrometer during the LAUTLOS campaign in Sodankylä, Finland, in January and February 2004. The retrieved H2O profiles reveal a detailed view on the Arctic lower stratospheric water vapour distribution, and provide a valuable dataset for the validation of model and satellite data. Analysing the measurements with the semi-lagrangian advection model MIMOSA, water vapour profiles typical for the polar vortex' interior and exterior have been identified, and laminae in the observed profiles have been correlated to filamentary structures in the potential vorticity field. Applying the validated MIMOSA transport scheme to specific humidity fields from operational ECMWF analyses, large discrepancies from the observed profiles arise. Although MIMOSA is able to reproduce weak water vapour filaments and improves the shape of the profiles compared to operational ECMWF analyses, both models reveal a dry bias of about 1 ppmv in the lower stratosphere above 400 K, accounting for a relative difference from the measurements in the order of 20%. The large dry bias in the analysis representation of stratospheric water vapour in the Arctic implies the need for future regular measurements of water vapour in the polar stratosphere to allow the validation and improvement of climate models.

Maturilli, M.; Fierli, F.; Yushkov, V.; Lukyanov, A.; Khaykin, S.; Hauchecorne, A.

2006-07-01

7

Measurements of condensation nuclei in the Airborne Arctic Stratospheric Expedition: Observations of particle production in the polar vortex  

SciTech Connect

The ER-2 Condensation Nucleus Counter (ER-2 CNC) was operated in the Airborne Arctic Stratospheric Expedition (AASE) in January and February 1989. The ER-2 CNC measures the mixing ratio of particles, CN, with diameters from approximately 0.02 {mu}m to approximately 1 {mu}m. The spatial distribution of CN in the Arctic polar vortex was found to resemble that measured in the Antarctic in the Spring of 1987. The vertical profile of CN in the vortex was lowered by subsidence. At altitudes above the minimum in the CN mixing ratio profile, CN mixing ratios correlated negatively with that of N{sub 2}O, demonstrating new particle production. CN serve as nuclei in the formation of Polar Stratospheric Clouds (PSC's) and the concentration of CN can affect PSC properties.

Wilson, J.C.; Stolzenburg, M.R. (Univ. of Denver, CO (USA)); Clark, W.E. (California Polytechnic State Univ., San Luis Obispo (USA)); Loewenstein, M.; Ferry, G.V.; Chan, K.R. (NASA Ames Research Center, Moffett Field, CA (USA))

1990-03-01

8

2009/10 Arctic polar vortex observed by ISS/JEM/SMILES  

NASA Astrophysics Data System (ADS)

Superocnducting Submillimeter-Wave Limb-Emission Sounder (SMILES) is a 4K cooled limb sounding instrument in the 625-650 GHz frequency region, onboard International Space Station (ISS). SMILES was jointly developed by Japan Aerospace Exploration Agency (JAXA) and National Institute of Information and Communications Technology (NICT). SMILES operated from Oct. 12, 2009 to Apr. 23, 2010. SMILES measured O3, H35Cl, H37Cl, ClO, HOCl, HO2, BrO, HNO3, CH3CN and O3 isotopes. Precision (random error) of SMILES ClO product is about 0.01 ppb. SMILES measured latitudinal region 38°S-65°N. On Jan. 23, 2010, HCl is about 1.6 ppbt at outside polar vortex and it is almost entirely converted to the ClO (1.6 to 2.0 ppbt). O3 destruction has occurred as much as 20% (from 4 ppmv to 3.2 ppmv) after 3 weeks of heterogeneous chemical process. We compared temperature, O3, HCl, ClO, of SMILES with those calculated from SD-WACCM (specified dynamics-WACCM, reproduction run using GEOS-5 meteoroogical data, ±15 mintes at the nearest spatial grid). It has been already known that the agreement between SMILES and SD-WACCM are quite excellent at outside polar vortex at all altitude region. We found that agreements inside polar vortex, in genral, are also good.

Suzuki, Makoto; Imai, Koji; Mitsuda, Chihiro; Sano, Takuki; Manago, Naohiro; Naito, Yoko; Akiyoshi, Hideharu

2012-07-01

9

Interannual Variability of No2 In The Winter Arctic Polar Vortex and Impact On Ozone Photochemical Destruction  

NASA Astrophysics Data System (ADS)

Though NOx species are not directly responsible for the ozone destruction during the winter in the polar stratosphere, they play a key role in the ozone loss mechanism Indeed, if not removed, they have the potential to deactivate chlorine and bromine active species and thus to stop the ozone loss process. Several processes are contributing to the NOx removal in the winter Arctic: a) the polar night during which NOx convert slowly at all altitudes into NOy; b) the conversion into the reservoir species ClONO2 and BrONO2 in presence of activated chlorine or bromine; c) the fast heterogeneous hydrolysis of N2O5 in HNO3 on PSCs - or denoxification - followed or not by irreversible removal by sedimentation of PSC particles into which HNO3 is adsorbed ­ or denitrification -. However, because of the temperature dependence of gas phase reactions rates as well as of the composition (ICE, NAT or STS), nature (liquid or solid) and size of PSC particles, the NOx concentration depends strongly on the evolution of stratospheric temperature during the winter. The aim of the presentation it to study the variability of NOx concentration and its impact on chlorine activation and ozone loss from NO2, OClO, BrO and ozone measured with a SAOZ spectrometer flown on short and long duration balloons in the polar Arctic vortex during four consecutive winters, 1997 to 2000, of very different temperature history, and simulated by the 3D CTM REPROBUS model.

Pommereau, J. P.; Denis, L.; Goutail, F.; Lefevre, F.

10

Ozone depletion in filaments of the Arctic Polar Vortex observed during the first Global Hawk UAS science mission  

NASA Astrophysics Data System (ADS)

One of the important potential uses of the NASA Global Hawk Unmanned Aircraft System (UAS) in scientific research is to study stratospheric ozone (O3) depletion in polar regions. Manned flights involve remote and hazardous duty, which pose great risks to pilots, crew, and scientists. Arctic ozone depletion observed in the spring of 2010 by satellites, manned aircraft campaigns, ground-base stations was less severe than that observed this year (2011). The Global Hawk UAS flight on 23 April 2010 was the first to observe ozone-depleted air with a UAS platform. Temperatures in the polar vortex were cold enough for Type II Polar Stratospheric Clouds (PSC) to form for a short period (days) at 50 hPa in 2010, and cold temperatures existed for almost 2 months for Type I PSC formation. Based on the NOAA Unmanned aircraft systems Chromatograph for Atmospheric Trace Species (UCATS) ozone versus nitrous oxide tracer correlation plot (below), there is 21% less ozone in air from a polar filament sampled on 7 April 2010 compared to the Arctic air sampled later on 23 April 2010. The NOAA UAS Fast Ozone Instrument showed a similar pattern with respect to N2O. Age-of-air values derived from on board SF6 observations were about 5 years in the filament versus about 3 years outside the filament in the subsequent polar flight. The Global Hawk UAS flights were part of the Global Hawk Pacific Experiment (GloPac), which demonstrated flights up to 28.6 hr duration, altitudes as high as 19.8 km and a maximum range of 9200 nm while carrying a payload of in situ and remote instrumentation for atmospheric chemical and aerosol tracers. This first science mission of the NASA Global Hawk UAS demonstrated its huge potential for stratospheric ozone research over remote and hazardous polar areas.

Elkins, J. W.; Hintsa, E. J.; Dutton, G. S.; Hall, B. D.; Moore, F. L.; Gao, R.; Oltmans, S. J.; Patrick, L.; Johnson, B. J.; Ray, E. A.; Nance, D.; Fahey, D. W.; Newman, P. A.

2011-12-01

11

Chemical Loss of Ozone in the Arctic Polar Vortex in the Winter of 1991-1992.  

National Technical Information Service (NTIS)

In situ measurements of chlorine monoxide, bromine monoxide, and ozone are extrapolated globally, with the use of meteorological tracers, to infer the loss rates for ozone in the Arctic lower stratosphere during the Airborne Arctic Stratospheric Expeditio...

R. J. Salawitch S. C. Wofsy E. W. Gottlieb L. R. Lait P. A. Newman M. R. Schoeberl S. E. Strahan M. Loewenstein J. R. Podolske K. R. Chan M. H. Proffitt D. W. Fahey K. K. Kelly C. R. Webster R. D. May D. Baumgardner J. E. Dye J. C. Wilson J. W. Elkins J. G. Anderson

1993-01-01

12

Chemical loss of ozone in the arctic polar vortex in the winter of 1991-1992.  

PubMed

In situ measurements of chlorine monoxide, bromine monoxide, and ozone are extrapolated globally, with the use of meteorological tracers, to infer the loss rates for ozone in the Arctic lower stratosphere during the Airborne Arctic Stratospheric Expedition II (AASE II) in the winter of 1991-1992. The analysis indicates removal of 15 to 20 percent of ambient ozone because of elevated concentrations of chlorine monoxide and bromine monoxide. Observations during AASE II define rates of removal of chlorine monoxide attributable to reaction with nitrogen dioxide (produced by photolysis of nitric acid) and to production of hydrochloric acid. Ozone loss ceased in March as concentrations of chlorine monoxide declined. Ozone losses could approach 50 percent if regeneration of nitrogen dioxide were inhibited by irreversible removal of nitrogen oxides (denitrification), as presently observed in the Antarctic, or without denitrification if inorganic chlorine concentrations were to double. PMID:17790349

Salawitch, R J; Wofsy, S C; Gottlieb, E W; Lait, L R; Newman, P A; Schoeberl, M R; Loewenstein, M; Podolske, J R; Strahan, S E; Proffitt, M H; Webster, C R; May, R D; Fahey, D W; Baumgardner, D; Dye, J E; Wilson, J C; Kelly, K K; Elkins, J W; Chan, K R; Anderson, J G

1993-08-27

13

Match observations in the Arctic winter 1996/97: High stratospheric ozone loss rates correlate with low temperatures deep inside the polar vortex  

NASA Astrophysics Data System (ADS)

With the Match technique, which is based on the coordinated release of ozonesondes, chemical ozone loss rates in the Arctic stratospheric vortex in early 1997 have been quantified in a vertical region between 400 K and 550 K. Ozone destruction was observed from mid February to mid March in most of these levels, with maximum loss rates between 25 and 45ppbv/day. The vortex averaged loss rates and the accumulated vertically integrated ozone loss have been smaller than in the previous two winters, indicating that the record low ozone columns observed in spring 1997 were partly caused by dynamical effects. The observed ozone loss is inhomogeneous through the vortex with the highest loss rates located in the vortex centre, coinciding with the lowest temperatures. Here the loss rates per sunlit hour reached 6 ppbv/h, while the corresponding vortex averaged rates did not exceed 3.9 ppbv/h.

Schulz, A.; Rex, M.; Steger, J.; Harris, N. R. P.; Braathen, G. O.; Reimer, E.; Alfier, R.; Beck, A.; Alpers, M.; Cisneros, J.; Claude, H.; De Backer, H.; Dier, H.; Dorokhov, V.; Fast, H.; Godin, S.; Hansen, G.; Kanzawa, H.; Kois, B.; Kondo, Y.; Kosmidis, E.; Kyrö, E.; Litynska, Z.; Molyneux, M. J.; Murphy, G.; Nakane, H.; Parrondo, C.; Ravegnani, F.; Varotsos, C.; Vialle, C.; Viatte, P.; Yushkov, V.; Zerefos, C.; von der Gathen, P.

14

The Potential for Ozone Depletion in the Arctic Polar Stratosphere  

NASA Astrophysics Data System (ADS)

The nature of the Arctic polar stratosphere is observed to be similar in many respects to that of the Antarctic polar stratosphere, where an ozone hole has been identified. Most of the available chlorine (HCl and ClONO_2) was converted by reactions on polar stratospheric clouds to reactive ClO and Cl_2O_2 throughout the Arctic polar vortex before midwinter. Reactive nitrogen was converted to HNO_3, and some, with spatial inhomogeneity, fell out of the stratosphere. These chemical changes ensured characteristic ozone losses of 10 to 15% at altitudes inside the polar vortex where polar stratospheric clouds had occurred. These local losses can translate into 5 to 8% losses in the vertical column abundance of ozone. As the amount of stratospheric chlorine inevitably increases by 50% over the next two decades, ozone losses recognizable as an ozone hole may well appear.

Brune, W. H.; Anderson, J. G.; Toohey, D. W.; Fahey, D. W.; Kawa, S. R.; Jones, R. L.; McKenna, D. S.; Poole, L. R.

1991-05-01

15

The potential for ozone depletion in the Arctic polar stratosphere  

SciTech Connect

The nature of the Arctic polar stratosphere is observed to be similar in many respects to that of the Antarctic polar stratosphere, where an ozone hole has been identified. most of the available chlorine (HCl and ClONO{sub 2}) was converted by reactions on polar stratospheric clouds to reactive ClO and Cl{sub 2}O{sub 2} throughout the Arctic polar vortex before midwinter. Reactive nitrogen was converted to HNO{sub 3}, and some, with spatial inhomogeneity, fell out of the stratosphere. These chemical changes ensured characteristic ozone losses of 10 to 15% at altitudes inside the polar vortex where polar stratospheric clouds had occurred. These local losses can translate into 5 to 8% losses in the vertical column abundance of ozone. As the amount of stratospheric chlorine inevitably increases by 50% over the next two decades, ozone losses recognizable as an ozone hole may well appear.

Brune, W.H. (Pennsylvania State Univ., University Park (United States)); Anderson, J.G.; Toohey, D.W. (Harvard Univ., Cambridge, MA (United States)); Fahey, D.W.; Kawa, S.R. (National Oceanic and Atmospheric Administration, Boulder, CO (United States)); Jones, R.L. (Univ. of Cambridge (England)); McKenna, D.S. (United Kingdom Meteorological Office, Berkshire (England)); Poole, L.R. (NASA Langley Research Center, Hampton, VA (United States))

1991-05-31

16

Transport out of the lower stratospheric Arctic vortex by Rossby wave breaking  

Microsoft Academic Search

The fine-scale structure in lower stratospheric tracer transport during the period of the two Arctic Airborne Stratospheric Expeditions (January and February 1989; December 1991 to March 1992) is investigated using contour advection with surgery calculations. These calculations show that Rossby wave breaking is an ongoing occurrence during these periods and that air is ejected from the polar vortex in the

D. W. Waugh; R. A. Plumb; R. J. Atkinson; R. J; M. R. Schoeberl; L. R. Lait; P. A; M. Loewenstein; D. W. Toohey; L. M. Avallone; C. R. Webster; R. D. May

1994-01-01

17

The Gravity Wave–Arctic Stratospheric Vortex Interaction  

Microsoft Academic Search

Four hundred and twenty-two nights of stratospheric gravity wave observations were obtained with a Rayleigh lidar in the High Arctic at Eureka (808N, 868W) during six wintertime measurement campaigns between 1992\\/ 93 and 1997\\/98. The measurements are grouped in positions relative to the arctic stratospheric vortex for comparison. Low gravity wave activity is found in the vortex core, outside of

Thomas J. Duck; James A. Whiteway; Allan I. Carswell

2001-01-01

18

Dynamics of Saturn's South Polar Vortex  

Microsoft Academic Search

We present observations of Saturn's south polar vortex (SPV) showing that it shares some properties with terrestrial hurricanes: cyclonic circulation, warm central region (the eye) surrounded by a ring of high clouds (the eye wall), and convective clouds outside the eye. The polar location and the absence of an ocean are major differences. It also shares properties with the polar

Ulyana A. Dyudina; Andrew P. Ingersoll; Shawn P. Ewald; Ashwin R. Vasavada; Robert A. West; Anthony D. Del Genio; John M. Barbara; Carolyn C. Porco; Richard K. Achterberg; F. Michael Flasar; Amy A. Simon-Miller; Leigh N. Fletcher

2008-01-01

19

Temporal development of ozone within the Arctic vortex during the winter of 1991/92  

SciTech Connect

This paper presents an attempt to look at the time development of ozone trends within the polar vortex. The EASOE campaign provided an unprecedented amount of information on ozone densities, and profiles, from sonde and other remote readings, over the European sector of the arctic. Here the authors look at trends on isentropic surfaces. The effort is directed at trying to identify chemically induced factors as the cause of the observed changes in ozone density, as opposed to air mass movement.

Braathen, G.O.; Dahlback, A. (Norwegian Institute for Air Research, Lillestrom (Norway)); Rummukainen, M.; Kyroe, E. (Finnish Meteorological Institute, Sodankylae (Finland)); Schmidt, U. (Institut fuer Atmosphaerische Chemie, Juelich (Germany)); Jorgensen, T.S. (Danish Meteorological Institute, Copenhagen (Denmark)); Fabian, R. (Univ. of Bremen (Germany)); Rudakov, V.V. (Central Aerological Observatory, Moscow (Russian Federation)); Gil, M. (Instituto Nacional de Tecnica Aerospacial, Madrid (Spain)); Borchers, R. (Max-Planck-Institut fuer Aeronomie, Kaltenberg-Lindau (Germany))

1994-06-22

20

QBO effects on Antarctic mesospheric winds and polar vortex dynamics  

NASA Astrophysics Data System (ADS)

A dynamical link is demonstrated between the equatorial quasi-biennial oscillation (QBO) and high-latitude mesospheric zonal winds recorded by an Imaging Doppler Interferometer (IDI) at Halley, Antarctica. Above ˜80 km eastward winds in winter (an extension of the polar vortex into the mesosphere) are strengthened under easterly 50 hPa QBO conditions. This is similar to the Holton-Tan effect in the stratosphere but working in opposition. The weak winter time zonal winds are shown to differ by up to 2.6 m/s dependent on QBO phase. In spring, zonal winds are most strongly correlated with the equatorial 25 hPa QBO and are significantly more westerly in November, an extension of the QBO response in the stratosphere below. It is suggested that QBO modulation of the vortex winds in the Antarctic mesosphere is dependent on planetary-wave activity from the Antarctic in winter and Arctic in spring.

Ford, E. A. K.; Hibbins, R. E.; Jarvis, M. J.

2009-10-01

21

Radiative Influence of Antarctica on the Polar-Night Vortex.  

NASA Astrophysics Data System (ADS)

Temperatures over the Antarctic plateau are sharply colder than those over its maritime surroundings. The sharp temperature contrast due to Antarctica is conveyed upward through 9.6-m absorption by ozone, which shapes the thermal structure in the stratosphere. The radiative impact of Antarctica on the polar stratosphere is investigated in three-dimensional integrations of the nonlinear primitive equations, coupled to a full radiative-transfer calculation that is performed with and without clouds. Cooling associated with Antarctica depresses radiative-equilibrium temperatures by as much as 10 K. This direct radiative influence emerges clearly at high latitudes of the lowermost stratosphere. It is accompanied elsewhere by temperature changes of opposite sign, which result indirectly through adiabatic warming by the induced residual meridional circulation. Collectively, these influences reinforce the polar-night vortex, shift the jet axis poleward, and intensify downward transport over the polar cap by the residual circulation. In this way, radiative forcing from below contributes significantly to the features that distinguish the Antarctic vortex from the Arctic vortex.

Francis, Gene L.; Salby, Murry L.

2001-05-01

22

Law of mass action in the Arctic lower stratospheric polar vortex January-March 2000: ClO scaling and the calculation of ozone loss rates in a turbulent fractal medium  

NASA Astrophysics Data System (ADS)

We consider the effects of power law scaling in the 1999-2000 Arctic lower stratospheric vortex from the point of view of the law of mass action and its application to the chemical kinetics of ozone loss embedded in a turbulent, macroscopic, fractal medium. The ER-2 observations of ClO obey power law scaling; the exponent varies with time in a manner shown to be consistent with the scaling of NOy and O3, via the influences of polar stratospheric clouds and actinic solar radiation. While the microscopic rate coefficient for ClO three-body recombination to the dimer applies as measured to three-dimensional volumes in which the sole transport mechanism is molecular diffusion, this cannot be true in the 2.56-dimensional space in which macroscopically fluctuating ClO reacts in the lower stratosphere. We show that the rate of loss of ozone via the ClO dimer mechanism is proportional to [ClO]2.20 in late January/early February and to [ClO]2.55 in March. Chemical ozone loss had already occurred by the date of the first flight, 20000120.

Tuck, Adrian F.; Hovde, Susan J.; Gao, Ru-Shan; Richard, Erik C.

2003-08-01

23

Polarization holography for vortex retarders recording.  

PubMed

We present an original static recording method for vortex retarders (VRs) made from liquid crystal polymers (LCPs) using the superimposition of several polarized beams. VRs are birefringent plates characterized by a rotation of their fast axis about their center. The new method is based on polarization holography and photo-orientable LCP. Combining several polarized beams induces the polarization patterns required for the recording process of VRs without mechanical action. A mathematical description of the method, the outcomes of the numerical simulations, and the first experimental results are presented. PMID:24085221

Piron, Pierre; Blain, Pascal; Habraken, Serge; Mawet, Dimitri

2013-10-01

24

Dynamics of Saturn's South Polar Vortex  

NASA Astrophysics Data System (ADS)

We present observations of Saturn's south polar vortex (SPV) showing that it shares some properties with terrestrial hurricanes: cyclonic circulation, warm central region (the eye) surrounded by a ring of high clouds (the eye wall), and convective clouds outside the eye. The polar location and the absence of an ocean are major differences. It also shares properties with the polar vortices on Venus, such as polar location, cyclonic circulation, warm center, and long lifetime, but the Venus vortices have cold collars and are not associated with convective clouds. The SPV's combination of properties is unique among vortices in the solar system.

Dyudina, Ulyana A.; Ingersoll, Andrew P.; Ewald, Shawn P.; Vasavada, Ashwin R.; West, Robert A.; Del Genio, Anthony D.; Barbara, John M.; Porco, Carolyn C.; Achterberg, Richard K.; Flasar, F. Michael; Simon-Miller, Amy A.; Fletcher, Leigh N.

2008-03-01

25

Vortex polarization states in nanoscale ferroelectric arrays.  

PubMed

Two-dimensional arrays of ferroelectric lead zirconate titanate (PZT) nanodots were fabricated using pulsed laser deposition through ultrathin anodic aluminum oxide membrane stencil masks. The static distribution of polarization configurations was investigated using in- and out-of-plane piezoresponse force microscopy (PFM). The observed presence of an in-plane polarization component in nominally (001) oriented PZT suggests the existence of a significant deviation from the regular tetragonal structure that allows the formation of complex core-polarization states. Core-polarization states may indicate the presence of quasi-toroidal polarization ordering. The experimental results are compared with a theoretical model to determine the fingerprint of a vortex polarization state in PFM. PMID:19191502

Rodriguez, B J; Gao, X S; Liu, L F; Lee, W; Naumov, I I; Bratkovsky, A M; Hesse, D; Alexe, M

2009-03-01

26

On the Origin of Polar Vortex Air  

NASA Astrophysics Data System (ADS)

The existence of the multi-year HALOE CH4 data set, together with some comparisons of forward with back trajectory calculations which we have carried out, has motivated us to reexamine the question of polar vortex descent. Three-dimensional diabatic trajectory calculations have been carried out for the seven month fall to spring period in both the northern hemisphere (NH) and southern hemisphere (SH) polar stratosphere for the years 1992-1999. These computations are compared to fixed descent computations where the parcels were fixed at their latitude-longitude locations and allowed to descend without circulating. The forward trajectory computed descent is always less than the fixed descent due to horizontal parcel motions and variations in heating rates with latitude and longitude. Although the forward calculations estimate the maximum amount of descent that can occur, they do not necessarily indicate the actual origin of springtime vortex air. This is because more equatorward air can be entrained within the vortex during its formation. To examine the origin of the spring vortex air, the trajectory model was run backward for seven months from spring to fall. The back trajectories show a complex distribution of parcels in which one population originates in the upper stratosphere and mesosphere and experiences considerable descent in the polar regions, while the remaining parcels originate at lower altitudes of the middle and lower stratosphere and are mixed into the polar regions during vortex formation without experiencing as much vertical transport. The amount of descent experienced by the first population shows little variability from year to year, while the computed descent and mixing of the remaining parcels show considerable interannual variability due to the varying polar meteorology. Because of this complex parcel distribution it is not meaningful to speak of a net amount of descent experienced over the entire winter period. Since the back trajectories indicate that much of the air can come from lower altitudes than would be implied by the forward calculations, using a comparison between pre-winter and post-winter tracer profiles to estimate the amount of descent over this period will give erroneous descent amounts. In order to evaluate the computed descent, spring methane amounts were computed by mapping HALOE fall observations onto the final latitude-altitude locations of the back trajectories. These locations indicate the origin of the spring vortex air. The agreement between the computed means and the spring HALOE means is generally within 0.1-0.2 ppmv in the NH and 0.1-0.4 ppmv in the SH.

Rosenfield, J. E.; Schoeberl, M. R.

2001-05-01

27

Vortex polarization dynamics in a square magnetic nanodot  

NASA Astrophysics Data System (ADS)

Langevin simulations at finite temperature of two-dimensional magnetic nanodots were performed using the Landau–Lifshitz equation with exchange and dipolar interactions. In a wide range of temperatures, the dynamics of square samples with one central vortex was studied, focusing on the out-of-plane magnetic component at the vortex-core. This vortex-core undergoes polarization sign reversals in a thermally activated process. In the intervals between polarization flips, the out-of-plane spin components at the vortex-core show oscillations with identifiable frequencies connected with certain eigenfrequencies of the system associated with polarity active modes. The vortex-core positions were also monitored.

Depondt, Ph; Lévy, J.-C. S.; Mamica, S.

2013-11-01

28

Dynamics of Saturn's south polar vortex.  

PubMed

The camera onboard the Cassini spacecraft has allowed us to observe many of Saturn's cloud features. We present observations of Saturn's south polar vortex (SPV) showing that it shares some properties with terrestrial hurricanes: cyclonic circulation, warm central region (the eye) surrounded by a ring of high clouds (the eye wall), and convective clouds outside the eye. The polar location and the absence of an ocean are major differences. It also shares properties with the polar vortices on Venus, such as polar location, cyclonic circulation, warm center, and long lifetime, but the Venus vortices have cold collars and are not associated with convective clouds. The SPV's combination of properties is unique among vortices in the solar system. PMID:18369142

Dyudina, Ulyana A; Ingersoll, Andrew P; Ewald, Shawn P; Vasavada, Ashwin R; West, Robert A; Del Genio, Anthony D; Barbara, John M; Porco, Carolyn C; Achterberg, Richard K; Flasar, F Michael; Simon-Miller, Amy A; Fletcher, Leigh N

2008-03-28

29

Loss of ozone in the Arctic vortex for the winter of 1989  

SciTech Connect

Measurements of ClO (Brune et al., 1990) acquired during the Airborne Arctic Stratospheric Expedition are used to infer concentrations of reactive chlorine (ClO + 2 {times} Cl{sub 2}O{sub 2}). Observed fields of potential temperature and potential vorticity are used to extrapolate in situ data to larger regions of the vortex. Calculated values of the loss rate of O{sub 3}, based on estimates of reactive chlorine and measurements of BrO (Toohey et al., 1990), suggest that the loss of O{sub 3} was about 12% for levels of the atmosphere with potential temperatures between 440 and 470 K over the 39 day duration of the ER-2 flights into the polar vortex. Calculated loss rates agree with observed rates of removal of O{sub 3}, although significant uncertainties exist for each.

Salawitch, R.J.; McElroy, M.B.; Yatteau, J.H.; Wofsy, S.C. (Harvard Univ., Cambridge, MA (USA)); Schoeberl, M.R.; Lait, L.R.; Newman, P.A. (NASA Goddard Space Flight Center, Greenbelt, MD (USA)); Chan, K.R.; Loewenstein, M.; Podolske, J.R.; Strahan, S.E. (NASA Ames Research Center, Moffett Field, CA (USA)); Proffitt, M.H. (NOAA Aeronomy Laboratory, Boulder, CO (USA) Univ. of Colorado, Boulder (USA))

1990-03-01

30

Loss of ozone in the Arctic vortex for the winter of 1989  

NASA Astrophysics Data System (ADS)

Measurements of ClO (Brune et al., 1990) acquired during the Airborne Arctic Stratospheric Expedition are used to infer concentrations of reactive chlorine (ClO + 2 x Cl2O2). Observed fields of potential temperature and potential vorticity are used to extrapolate in situ data to larger regions of the vortex. Calculated values of the loss rate of O3, based on estimates of reactive chlorine and measurements of BrO (Toohey et al., 1990), suggest that the loss of O3 was abut 12 pct for levels of the atmosphere with potential temperatures between 440 and 470 K over the 39 day duration of the ER-2 flights into the polar vortex. Calculated loss rates agree with observed rates of removal of O3, although significant uncertainties exist for each.

Salawitch, Ross J.; McElroy, Michael B.; Yatteau, John H.; Schoeberl, Mark R.; Lait, Leslie R.; Newman, Paul A.; Chan, K. Roland; Loewenstein, Max; Podolske, James R.; Strahan, Susan E.

1990-03-01

31

Ozone depletion in the Arctic vortex at Alert during February 1989  

SciTech Connect

Evidence for an apparent chemical depletion of ozone was observed in the Arctic polar vortex during February 1989 in the form of a depleted layer in the ozone mixing ratio altitude profile. The measurements of the distribution of ozone partial pressure in the polar vortex were conducted with ECC ozonesondes which covered the altitude range from 1 to 30 km. These balloon measurements demonstrated a depleted layer in the profile at altitudes from 18 to 24 km. The meteorological ozonesonde balloon ascents took place from January 24 to February 22, 1989 from Alert, Canada at 82.5 N. A comparison of the late February ozone profiles with the late January ozone profiles indicates that the depletion was due to a process which may have occurred while the polar air was partially in sunlight. The depleted layer was similar to that observed from the South Pole base in the Antarctic inside the ozone hole in mid-September. The depletion may have commenced at high altitudes above 22 km and moved downwards during February in a manner similar to the process in September in the Antarctic. Polar stratospheric clouds were previously observed in mid-January over the altitude regime from 16 to 24 km.

Evans, W.F.J. (Atmospheric Environment Service, Downsview, Ontario (Canada))

1990-02-01

32

Middle-high latitude N2O distributions related to the arctic vortex breakup  

NASA Astrophysics Data System (ADS)

The relationship of N2O distributions with the Arctic vortex breakup is first analyzed with a probability distribution function (PDF) analysis. The N2O concentration shows different distributions between the early and late vortex breakup years. In the early breakup years, the N2O concentration shows low values and large dispersions after the vortex breakup, which is related to the inhomogeneity in the vertical advection in the middle and high latitude lower stratosphere. The horizontal diffusion coefficient (K,,) shows a larger value accordingly. In the late breakup years, the N2O concentration shows high values and more uniform distributions than in the early years after the vortex breakup, with a smaller vertical advection and K,, after the vortex breakup. It is found that the N2O distributions are largely affected by the Arctic vortex breakup time but the dynamically defined vortex breakup time is not the only factor.

Zhou, L. B.; Zou, H.; Gao, Y. Q.

2006-03-01

33

Electrical measurements of the polarization in a moving magnetic vortex  

NASA Astrophysics Data System (ADS)

We propose that the polarization of the moving magnetic vortex core can be detected by the electro- and spin-motive forces acting on the spin-polarized conduction electrons. With parameters appropriate to Permalloy, we have simulated the dynamics of a magnetic vortex core resulting from an applied oscillating magnetic field. We show that the polarization of the moving core can be detected by a simple electrical measurement.

Ohe, Jun-Ichiro; Barnes, Stewart E.; Lee, Hyun-Woo; Maekawa, Sadamichi

2009-09-01

34

Investigation of Ch4 and Cfc-11 Vertical Profiles In The Arctic Vortex During The Solve/theseo 2000 Campaign.  

NASA Astrophysics Data System (ADS)

Simultaneous balloon-borne measurements of ozone and long-lived tracers were made in Esrange, Sweden (68N, 22E), during the 1999/2000 winter as part of the SOLVE/THESEO 2000 campaign. Here we present the data from two lightweight instruments. A near-infrared tunable diode laser absorption spectrometer (TDLAS) making high spatial resolution in situ measurements of methane and the DIRAC in situ gas chromatograph measuring CFCs. We compare our tracer vertical profiles with a number of instruments on board of balloon and aircraft platforms and calculate the ozone loss inside the Arctic vortex between late January and early March using the relation between long-lived tracers and O3. In order for the 3-D Chemical Transport Models to quantify the rate of chemically induced ozone loss as a function of time both inside the Arctic vortex and at mid- latitudes, the models must correctly describe atmospheric transport. Results from the REPROBUS and the SLIMCAT 3D CTMs are tested using the tracers measurements made by the TDLAS and the DIRAC instruments and the high-resolution PV advec- tion contour MIMOSA model. The analysis shows that measurements are in good agreement with the 3D models inside the polar vortex but there are differences when measurements where performed near the edge of the vortex.

Garcelon, S.; Gardiner, T. D.; Hansford, G. M.; Harris, N. R. P.; Howieson, I. H.; Jones, R. L.; McIntyre, J. D.; Pyle, J. A.; Robinson, A. D.; Swann, N. R.; Woods, P. T.

35

N[sub 2]O as an indicator of Arctic vortex dynamics: Correlations with O[sub 3] over Thule, Greenland in February and March, 1992  

SciTech Connect

The authors have recovered vertical profiles of stratospheric N[sub 2]O from spectra observed using a ground-based mm-wave spectrometer during the Arctic spring. The measurements were made from Thule, Greenland (76.3[degrees]N, 68.4[degrees]W) on nine occasions from late February to late March, 1992 as part of the Upper Atmosphere Research Satellite (UARS) Correlative Measurements Program and the European Arctic Stratospheric Ozone Experiment (EASOE). During late February Thule was under the inside edge of the Arctic vortex and mixing ratio profiles measured in that period are substantially reduced from typical high-latitude summer values. By late March the polar vortex had moved well away from Thule and N[sub 2]O mixing ratios were greatly increased, coinciding with a basic change in circulation that brought in air from the Aleutian high. The motion of the vortex is also illustrated in the change in potential vorticity above Thule. A correlation with ozone balloonsonde data from Thule is made and compared to similar analyses of the Airborne Arctic Stratospheric Expedition (AASE) measurements. Within the sensitivity of the authors' analysis, the correlation of N[sub 2]O and O[sub 3] show no evidence of ozone depletion within the vortex during this period; however, there is a distinct difference in the correlation inside and outside the vortex. 13 refs., 5 figs.

Emmons, L.K.; Reeves, J.M.; Shindell, D.T.; Zafra, R.L. de (State Univ. of New York, Stony Brook, NY (United States))

1994-06-22

36

Balloon-borne In-Situ Measurements of ClO and ClONO2 in the late 2010/2011 Arctic Polar Vortex: Instrument Calibration and Results  

NASA Astrophysics Data System (ADS)

Since 1995 we have carried out balloon-borne in-situ measurements of ClO and BrO. Lately we have designed an upgraded balloon instrument to additionally measure the ClO dimer and the reservoir species ClONO2. The halogen oxide measurements are carried out employing the chemical conversion resonance fluorescence technique (Brune et al., 1989) in a fast flow through two parallel ducts generated by modified roots blowers. The inlet of one duct is equipped with a dedicated heating element enabling controlled air temperatures in excess of 550K at pressures lower than 50 hPa. This causes the ClO dimer to thermolyze forming two ClO molecules at around 380K as well as additional thermolysis of ClONO2 to ClO and NO2 at around 540K. The ClO generated within the thermolysis is then detected on top of the ambient ClO. Temperature cycling and intercomparisons with the first unheated duct allow the differentiation of the chlorine species. Details of the instrumental setup, instrument calibration, and performance will be discussed. Profiles for ClO and ClONO2 from a flight carried out from ESRANGE near Kiruna, Sweden, on April-01-2011 in the edge region of the degrading arctic vortex will be presented marking the first ClONO2 in-situ measurements above research aircraft altitudes (20km). Brune, W. H., et al., Insitu Observations Of ClO In The Antarctic - Er-2 Aircraft Results From 54-Degrees-S To 72-Degrees-S Latitude, Journal Of Geophysical Research-Atmospheres, 94, 16649-16663, 1989.

Stroh, F.; Heinecke, F.; Afchine, A.; Barthel, J.; Engel, A.; Grooß, J.; von Hobe, M.; Richter, A.; Schönfeld, A.; Suminska, O.; Tan, V.

2011-12-01

37

Chemical ozone losses in Arctic and Antarctic polar winter/spring season derived from SCIAMACHY limb measurements 2002-2009  

NASA Astrophysics Data System (ADS)

Stratospheric ozone profiles are retrieved for the period 2002-2009 from SCIAMACHY measurements of limb-scattered solar radiation in the Hartley and Chappuis absorption bands of ozone. This data set is used to determine the chemical ozone losses in both the Arctic and Antarctic polar vortices by averaging the ozone in the vortex at a given potential temperature. The chemical ozone losses at isentropic levels between 450 K and 600 K are derived from the difference between observed ozone abundances and the ozone modelled taking diabatic cooling into account, but no chemical ozone loss. Chemical ozone losses of up to 30-40% between mid-January and the end of March inside the Arctic polar vortex are reported. Strong inter-annual variability of the Arctic ozone loss is observed, with the cold winters 2004/2005 and 2006/2007 showing chemical ozone losses inside the polar vortex at 475 K, where 1.7 ppmv and 1.4 ppmv of ozone were removed, respectively, over the period from 22 January to beginning of April and 0.9 ppmv and 1.2 ppmv, respectively, during February. For the winters of 2007/2008 and 2002/2003, ozone losses of about 0.8 ppmv and 0.4 ppmv, respectively are estimated at the 475 K isentropic level for the period from 22 January to beginning of April. Essentially no ozone losses were diagnosed for the relatively warm winters of 2003/2004 and 2005/2006. The maximum ozone loss in the SCIAMACHY data set was found in 2007 at the 600 K level and amounted to about 2.1 ppmv for the period between 22 January and the end of April. Enhanced losses close to this altitude were found in all investigated Arctic springs, in contrast to Antarctic spring. The inter-annual variability of ozone losses and PSC occurrence rates observed during Arctic spring is consistent with the known QBO effects on the Arctic polar vortex, with exception of the unusual Arctic winter 2008/2009. The maximum total ozone mass loss of about 25 million tons was found in the cold Arctic winter of 2004/2005 inside the polar vortex between the 450 K and 600 K isentropic levels from mid-January until the middle of March. The Antarctic vortex averaged ozone loss as well as the size of the polar vortex do not vary much from year to year. The total ozone mass loss inside the Antarctic polar vortex between the 450 K and 600 K isentropic levels is about 50-60 million tons and the vortex volume for this altitude range varies between about 150 and 300 km3 for the period between mid-August and mid-November of every year studied, except for 2002. In 2002 a mid-winter major stratospheric warming occurred in the second half of September and the ozone mass loss was only about half of the value in the other years. However, inside the polar vortex we find chemical ozone losses at the 475 K isentropic level that are similar to those in all other years studied. At this isentropic level ozone losses of 70-90% between mid-August and mid-November or about 2.5 ppmv are observed every year. At isentropic levels above 500 K the chemical ozone losses were found to be larger in 2002 than in all other years studied. Comparisons of the vertical variation of ozone losses derived from SCIAMACHY observations with several independent techniques for the Arctic winter 2004/2005 show that the SCIAMACHY results fall in the middle of the range of previously published results for this winter. For other winters in both hemispheres - for which comparisons with other studies were possible - the SCIAMACHY results are consistent with the range of previously published results.

Sonkaew, T.; von Savigny, C.; Eichmann, K.-U.; Weber, M.; Rozanov, A.; Bovensmann, H.; Burrows, J. P.; Grooß, J.-U.

2013-02-01

38

An Investigation of CIO Photchemistry in the Chemically Perturbed Arctic Vortex  

Microsoft Academic Search

A new lightweight in situ instrument designed to measure ClO was flown on a balloon launched into the arctic vortex at dawn on February 3, 1995 at Kiruna, Sweden during the Second European Stratospheric Arctic and Mid-latitude Experiment (SESAME), together with instruments to measure ozone and long-lived tracers. Observations on ascent and descent at different solar zenith angles are compared

J. M. Pierson; K. A. McKinney; D. W. Toohey; J. Margitan; U. Schmidt; A. Engel; P. A. Newman

1999-01-01

39

Airborne Lidar Studies of Arctic Polar Stratospheric Clouds.  

National Technical Information Service (NTIS)

Airborne lidar measurements of Arctic polar stratospheric clouds (PSC) in January 1984 and January 1986 are reported. The locales and altitudes of the clouds coincided in both years with very cold ambient temperatures. Enhancements in aerosol backscatteri...

L. R. Poole

1987-01-01

40

The 2009-2010 Arctic polar stratospheric cloud season: a CALIPSO perspective  

NASA Astrophysics Data System (ADS)

Spaceborne lidar measurements from CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) are used to provide a vortex-wide perspective of the 2009-2010 Arctic polar stratospheric cloud (PSC) season to complement more focused measurements from the European Union RECONCILE (reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions) field campaign. The 2009-2010 Arctic winter was unusually cold at stratospheric levels, especially from mid-December 2009 until the end of January 2010, and was one of only a few winters from the past 52 years with synoptic-scale regions of temperatures below the frost point. More PSCs were observed by CALIPSO during the 2009-2010 Arctic winter than in the previous three Arctic seasons combined. In particular, there were significantly more observations of high number density nitric acid trihydrate (NAT) mixtures (referred to as Mix 2-enh) and ice PSCs. We found that the 2009-2010 season could roughly be divided into four periods with distinctly different PSC optical characteristics. The early season (15-30 December 2009) was characterized by patchy, tenuous PSCs, primarily low number density liquid/NAT mixtures. The second phase of the season (31 December 2009-14 January 2010) was characterized by frequent mountain wave ice clouds that nucleated widespread NAT particles throughout the vortex, including Mix 2-enh. The third phase of the season (15-21 January 2010) was characterized by synoptic-scale temperatures below the frost point which led to a rare outbreak of widespread ice clouds. The fourth phase of the season (22-28 January) was characterized by a major stratospheric warming that distorted the vortex, displacing the cold pool from the vortex center. This final phase was dominated by supercooled ternary solution (STS) PSCs, although NAT particles may have been present in low number densities, but were masked by the more abundant STS droplets at colder temperatures. We also found distinct variations in the relative proportion of PSCs in each composition class with altitude over the course of the 2009-2010 Arctic season. Lower number density liquid/NAT mixtures were most frequently observed in the lower altitude regions of the clouds (below ∼18-20 km), which is consistent with CALIPSO observations in the Antarctic. Higher number density liquid/NAT mixtures, especially Mix 2-enh, were most frequently observed at altitudes above 18-20 km, primarily downstream of wave ice clouds. This pattern is consistent with the conceptual model whereby low number density, large NAT particles are precipitated from higher number density NAT clouds (i.e. mother clouds) that are nucleated downstream of mountain wave ice clouds.

Pitts, M. C.; Poole, L. R.; Dörnbrack, A.; Thomason, L. W.

2010-10-01

41

Titan's winter polar vortex structure revealed by chemical tracers  

Microsoft Academic Search

The winter polar vortex on Saturn's largest moon Titan has profound effects on atmospheric circulation and chemistry and for the current northern midwinter season is the major dynamical feature of Titan's stratosphere and mesosphere. We use 2 years of observations from Cassini's composite infrared spectrometer to determine cross sections of five independent chemical tracers (HCN, HC3N, C2H2, C3H4, and C4H2),

N. A. Teanby; R. de Kok; P. G. J. Irwin; S. Osprey; S. Vinatier; P. J. Gierasch; P. L. Read; F. M. Flasar; B. J. Conrath; R. K. Achterberg; B. Bézard; C. A. Nixon; S. B. Calcutt

2008-01-01

42

Stratospheric water vapour as tracer for Vortex filamentation in the Arctic winter 2002/2003  

NASA Astrophysics Data System (ADS)

Balloon-borne frost point hygrometers measured three high-resolution profiles of stratospheric water vapour above Ny-Ålesund, Spitsbergen during winter 2002/2003. The profiles obtained on 12 December 2002 and on 17 January 2003 provide an insight into the vertical distribution of water vapour in the core of the polar vortex. The water vapour sounding on 11 February 2003 was obtained within the vortex edge region of the lower stratosphere. Here, a significant reduction of water vapour mixing ratio was observed between 16 and 19 km. The stratospheric temperatures indicate that this dehydration was not caused by the presence of polar stratospheric clouds or earlier PSC particle sedimentation. Ozone observations on this day indicate a large scale movement of the polar vortex and show laminae in the same altitude range as the water vapour profile. The link between the observed water vapour reduction and filaments in the vortex edge region is indicated in the results of the semi-lagrangian advection model MIMOSA, which show that adjacent filaments of polar and mid latitude air can be identified above the Spitsbergen region. A vertical cross-section produced by the MIMOSA model reveals that the water vapour sonde flew through polar air in the lowest part of the stratosphere below 425 K, then passed through filaments of mid latitude air with lower water vapour concentrations, before it finally entered the polar vortex above 450 K. These results indicate that on 11 February 2003 the frost point hygrometer measured different water vapour concentrations as the sonde detected air with different origins. Instead of being linked to dehydration due to PSC particle sedimentation, the local reduction in the stratospheric water vapour profile was in this case caused by dynamical processes in the polar stratosphere.

Müller, M.; Neuber, R.; Fierli, F.; Hauchecorne, A.; Vömel, H.; Oltmans, S. J.

2003-11-01

43

Stratospheric water vapour as tracer for vortex filamentation in the Arctic winter 2002/2003  

NASA Astrophysics Data System (ADS)

During winter 2002/2003, three balloon-borne frost point hygrometers measured high-resolution profiles of stratospheric water vapour above Ny-Ålesund, Spitsbergen. All measurements reveal a high H2O mixing ratio of about 7 ppmv above 24 km, thus differing significantly from the 5 ppmv that are commonly assumed for the calculation of polar stratospheric cloud existence temperatures. The profiles obtained on 12 December 2002 and on 17 January 2003 provide an insight into the vertical distribution of water vapour in the core of the polar vortex. Unlike the earlier profiles, the water vapour sounding on 11 February 2003 detected the vortex edge region in the lower part of the stratosphere. Here, a striking diminuition in H2O mixing ratio stands out between 16 and 19 km. The according stratospheric temperatures clarify that this dehydration can not be caused by the presence of polar stratospheric clouds or earlier PSC particle sedimentation. On the same day, ozone observations by lidar indicate a large scale movement of the polar vortex, while an ozone sonde measurement even shows laminae in the same altitude range as in the water vapour profile. Tracer lamination in the vortex edge region is caused by filamentation of the vortex. The link between the observed water vapour diminuition and filaments in the vortex edge region is highlighted by results of the MIMOSA contour advection model. In the altitude of interest, adjoined filaments of polar and mid-latitudinal air can be identified above the Spitsbergen region. A vertical cross-section reveals that the water vapour sonde has flown through polar air in the lowest part of the stratosphere. Where the low water vapour mixing ratio was detected, the balloon passed through air from a mid-latitudinal filament from about 425 to 445 K, before it finally entered the polar vortex above 450 K. The MIMOSA model results elucidate the correlation that on 11 February 2003 the frost point hygrometer measured strongly variable water vapour concentrations as the sonde detected air with different origins, respectively. Instead of being linked to dehydration due to PSC particle sedimentation, the local diminuition in the stratospheric water vapour profile of 11 February 2003 has been found to be caused by dynamical processes in the polar stratosphere.

Müller, M.; Neuber, R.; Fierli, F.; Hauchecorne, A.; Vömel, H.; Oltmans, S. J.

2003-08-01

44

Vortex oscillations induced by spin-polarized current in a magnetic nanopillar: Analytical versus micromagnetic calculations  

NASA Astrophysics Data System (ADS)

We investigate the vortex excitations induced by a spin-polarized current in a magnetic nanopillar by means of micromagnetic simulations and analytical calculations. Damped motion, stationary vortex rotation and the switching of the vortex core are successively observed for increasing values of the current. We demonstrate that even for small amplitude of the vortex motion, the analytical description based on the classical Thiele approach can yield quantitatively and qualitatively unsound results. We show that the energy dissipation function, which is calculated respecting rotational motion of the vortex, can be used for qualitative analytical description of the system.

Khvalkovskiy, A. V.; Grollier, J.; Dussaux, A.; Zvezdin, Konstantin A.; Cros, V.

2009-10-01

45

Chlorine chemistry on polar stratospheric cloud particles in the arctic winter.  

PubMed

Simultaneous in situ measurements of hydrochloric acid (HCl) and chlorine monoxide (ClO) in the Arctic winter vortex showed large HCl losses, of up to 1 part per billion by volume (ppbv), which were correlated with high ClO levels of up to 1.4 ppbv. Air parcel trajectory analysis identified that this conversion of inorganic chlorine occurred at air temperatures of less than 196 +/- 4 kelvin. High ClO was always accompanied by loss of HCI mixing ratios equal to (1/2)(ClO + 2Cl(2)O(2)). These data indicate that the heterogeneous reaction HCl + ClONO(2) --> Cl(2) + HNO(3) on particles of polar stratospheric clouds establishes the chlorine partitioning, which, contrary to earlier notions, begins with an excess of ClONO(2), not HCl. PMID:17790344

Webster, C R; May, R D; Toohey, D W; Avallone, L M; Anderson, J G; Newman, P; Lait, L; Schoeberl, M R; Elkins, J W; Chan, K R

1993-08-27

46

Chlorine chemistry on polar stratospheric cloud particles in the Arctic winter  

SciTech Connect

Simultaneous in situ measurements of hydrochloric acid (HCl) and chlorine monoxide (ClO) in the Arctic winter vortex showed large HCl losses, of up to 1 part per billion by volume (ppbv), which were correlated with high ClO levels of up to 1.4 ppbv. Air parcel trajectory analysis identified that this conversion of inorganic chlorine occurred at air temperatures of less than 196 [plus minus]4 kelvin. High ClO was always accompanied by loss of HCl mixing ratios equal to 1/2(ClO + 2Cl[sub 2]O[sub 2]). These data indicate that the heterogeneous reaction HCl + ClONO[sub 2] [yields] Cl[sub 2] + HNO[sub 3] on particles of polar stratospheric clouds establishes the chlorine partitioning, which, contrary to earlier notions, begins with an excess of ClONO[sub 2], not HCl.

Webster, C.R.; May, R.D. (California Institute of Technology, Pasadena, CA (United States)); Toohey, D.W. (Univ. of California, Irvine, CA (United States)); Avallone, L.M.; Anderson, J.G. (Harvard Univ., Cambridge, MA (United States)); Newman, P.; Lait, L.; Schoeberl, M.R. (National Aeronautics and Space Administration, Greenbelt, MD (United States)); Elkins, J.W. (National Oceanographic and Atmospheric Agency, Boulder, CO (United States)); Chan, K.R. (NASA Ames Research Center, Moffett Field, CA (United States))

1993-08-27

47

The 2009-2010 Arctic polar stratospheric cloud season: a CALIPSO perspective  

NASA Astrophysics Data System (ADS)

Spaceborne lidar measurements from CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) are used to provide a vortex-wide perspective of the 2009-2010 Arctic PSC (polar stratospheric cloud) season to complement more focused measurements from the European Union RECONCILE (reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions) field campaign. The 2009-2010 Arctic winter was unusually cold at stratospheric levels from mid-December 2009 until the end of January 2010, and was one of only a few winters from the past fifty-two years with synoptic-scale regions of temperatures below the frost point. More PSCs were observed by CALIPSO during the 2009-2010 Arctic winter than in the previous three Arctic seasons combined. In particular, there were significantly more observations of high number density NAT (nitric acid trihydrate) mixtures (referred to as Mix 2-enh) and ice PSCs. We found that the 2009-2010 season could roughly be divided into four periods with distinctly different PSC optical characteristics. The early season (15-30 December 2009) was characterized by patchy, tenuous PSCs, primarily low number density liquid/NAT mixtures. No ice clouds were observed by CALIPSO during this early phase, suggesting that these early season NAT clouds were formed through a non-ice nucleation mechanism. The second phase of the season (31 December 2009-14 January 2010) was characterized by frequent mountain wave ice clouds that nucleated widespread NAT particles throughout the vortex, including Mix 2-enh. The third phase of the season (15-21 January 2010) was characterized by synoptic-scale temperatures below the frost point which led to a rare outbreak of widespread ice clouds. The fourth phase of the season (22-28 January) was characterized by a major stratospheric warming that distorted the vortex, displacing the cold pool from the vortex center. This final phase was dominated by STS (supercooled ternary solution) PSCs, although NAT particles may have been present in low number densities, but were masked by the more abundant STS droplets at colder temperatures. We also found distinct variations in the relative proportion of PSCs in each composition class with altitude over the course of the 2009-2010 Arctic season. Lower number density liquid/NAT mixtures were most frequently observed in the lower altitude regions of the clouds (below ~18-20 km), which is consistent with CALIPSO observations in the Antarctic. Higher number density liquid/NAT mixtures, especially Mix 2-enh, were most frequently observed at altitudes above 18-20 km, primarily downstream of wave ice clouds. This pattern is consistent with the conceptual model whereby low number density, large NAT particles are precipitated from higher number density NAT clouds (i.e. mother clouds) that are nucleated downstream of mountain wave ice clouds.

Pitts, M. C.; Poole, L. R.; Dörnbrack, A.; Thomason, L. W.

2011-03-01

48

Polar Gateways Arctic Circle Sunrise 2008 Conference at the Top of the World  

Microsoft Academic Search

The Polar Gateways conference was hosted during January 23-29, 2008, the first week of polar sunrise at Barrow, Alaska, at the new Barrow Arctic Research Center of the Barrow Arctic Science Consortium (BASC). The dawn week of polar day, the highly variable low temperatures, and the ice-covered shore tundra and adjacent sea ice conditions provided an appropriate locale for a

J. F. Cooper; K. Kauristie; A. T. Weatherwax; G. W. Sheehan; R. W. Smith; T. D. Cline; E. M. Lewis; G. Haines-Stiles

2008-01-01

49

OMAE 1996 -- Proceedings of the 15. international conference on offshore mechanics and arctic engineering. Volume 4: Arctic\\/polar technology  

Microsoft Academic Search

Volume 4 contains papers on the following topics: arctic\\/polar technology and development; ice properties; ice engineering; applied ice mechanics; ice-structure interaction; arctic structures and operations; frozen soil properties; and Russian Arctic development. In addition to the regular topics covered in OMAE conferences, there has been a special workshop as part of this year`s conference. In keeping with issues of current

W. A. Nixon; D. S. Sodhi; K. P. Kennedy; H. Yamaguchi; W. Bugno

1996-01-01

50

All-fiber polarization-dependent optical vortex beams generation via flexural acoustic wave.  

PubMed

We report on a novel type of optical mode conversion in fiber acousto-optics. The all-fiber narrowband complete transformation of the fundamental mode into the frequency downshifted optical vortex beam of topological charge +1 or -1 via a lowest-order flexural acoustic wave is theoretically demonstrated. Moreover, such a process is found to be polarization dependent: both the topological charge and polarization state of the produced optical vortex are governed by the circular polarization handedness of the input mode. The possible applications of the established conversion for optical vortex manipulation are discussed. PMID:24104673

Yavorsky, M A

2013-08-15

51

Spin-transfer force acting on vortex induced by current gradient in a planar polarizer geometry  

NASA Astrophysics Data System (ADS)

We discuss a new mechanism of changing the magnetic vortex gyrotropic motion in a permalloy/nonmagnet bi-layers system. In this system, a spin current characterized by an in-plane polarizer is injected from the nonmagnetic layer to the permalloy disk. We introduce current density gradient to the spin current, and find that the interplay between the planar polarizer and current gradient can change the damping of the vortex motion. This change originates from a spin-transfer force acting on the vortex. The influence of the spin-transfer force on the vortex motion is dependent on the direction of the planar polarizer, the orientation of the current density gradient, and the vortex state.

Liu, Yan; Li, Huanan; Hu, Yong; Du, An

2013-09-01

52

Polar Gas to pick route for Arctic Y Line  

SciTech Connect

Polar Gas Project is considering four possible Y line routes to move gas reserves from the Arctic Islands and the MacKenzie Delta/Beaufort Sea areas to southern Canada. All four routes are west of the single line route proposed by Polar Gas Ltd. in 1977 to run from the Arctic Islands to Longlac, Ontario, and would connect with existing pipelines at either Longlac, Winnipeg, Calgary, or Edmonton. Marketable reserves in the High Arctic Islands are estimated at 12.7 trillion cubic feet, not counting 3-6 trillion cubic feet probably contained in recent discoveries; the MacKenzie Delta reserves are estimated at 5.8 trillion cubic feet. The gas will be chilled to 0C for passage through permafrost regions, to prevent thawing of the soil, but the gas will be at higher temperatures in other areas, with various construction techniques used to protect the area of discontinuous permafrost from thawing. More than $70 million has been spent on project studies. An application will be filed in 1981, and the pipeline could be completed in 7-10 years.

Not Available

1980-05-26

53

Adaptations by the Arctic Fox (Alopex lagopus) to the Polar Winter  

Microsoft Academic Search

ABSTRACT. In this article physiological, behavioural and morphological adaptations by the arctic fox to low temperatures and food scarcity in winter are discussed. The arctic fox (Alopex lagopus) adapts to the low polar winter temperatures as a result of the excellent insulative properties of its fur. Among mammals, the arctic fox has the best insulative fur of all. The lower

Pal Prestrud

54

The surficial geology of the Canadian eastern Arctic and Polar continental shelves  

Microsoft Academic Search

We divide the Arctic continental shelf of Canada into three regions: (1) the Baffin Shelf, (2) the Arctic Channels and (3) the Polar Shelf. All are deep ice-dominated shelves largely floored by relict sediments. Iceberg scours occur to depths of 315 m on the Baffin Shelf but scours at depths deeper than this, and most in the Arctic Channels, are

John T. Andrews; A. E. Jennings; B. Maclean; P. J. Mudie; D. Praeg; G. Vilks

1991-01-01

55

Evolution of inorganic chlorine partitioning in the Arctic polar vortex  

Microsoft Academic Search

The first simultaneous, in situ atmospheric measurements of ClO, ClOOCl, ClONO2, and HCl, which together nearly compose total inorganic chlorine, Cly, were obtained using the NASA ER-2 aircraft, deployed from Kiruna, Sweden, during the SOLVE\\/THESEO mission. These chlorine measurements, along with Cly inferred from in situ measurements of organic chlorine source gases, offer an unprecedented opportunity to observe chlorine activation

D. M. Wilmouth; R. M. Stimpfle; J. G. Anderson; J. W. Elkins; D. F. Hurst; R. J. Salawitch; L. R. Lait

2006-01-01

56

Frequency generation by a magnetic vortex-antivortex dipole in spin-polarized current  

Microsoft Academic Search

We study the dynamics of a vortex-antivortex (VA) dipole which may be generated due to spin-polarized current flowing through a magnetic element. We employ the Landau-Lifshitz equation with a Slonczewski spin-torque term with in-plane polarization. We establish that the vortex dipole is set in steady-state rotational motion. The frequency of rotation is due to two independent forces: the interaction between

Stavros Komineas

2012-01-01

57

Determination of magnetic vortex polarity from a single Lorentz Fresnel image.  

SciTech Connect

Nanoscale confinement of the magnetization in a magnetic element often results in the creation of a vortex structure. The vortex equilibrium state is characterized by the curling of the in-plane magnetization (chirality) and an out-of-plane core magnetization. The polarity of the vortex core can point up or down, independent of the chirality, and, thus, magnetic elements with a vortex core are interesting as four-state logic elements. We present an easy-to-use, quantitative method for the determination of both chirality and polarity from a single Fresnel image. This method offers direct evidence of the three-dimensional structure of a magnetic vortex and has significant advantages over the more complex methods currently in use.

Phatak, C.; Tanase, M.; Petford-Long, A. K.; De Graef, M.; Materials Science Division; Carnegie Mellon Univ.

2009-01-01

58

Saturn's south polar vortex compared to other large vortices in the Solar System  

NASA Astrophysics Data System (ADS)

Observations made by the Imaging Science Subsystem (ISS), Visible and Infrared Mapping Spectrometer (VIMS) and the long-wavelength Composite Infrared Spectrometer (CIRS) aboard the Cassini spacecraft reveal that the large, long-lived cyclonic vortex at Saturn's south pole has a 4200-km-diameter cloud-free nearly circular region. This region has a 4 K warm core extending from the troposphere into the stratosphere, concentric cloud walls extending 20-70 km above the internal clouds, and numerous external clouds whose anticyclonic vorticity suggests a convective origin. The rotation speeds of the vortex reach 150±20 ms. The Saturn polar vortex has features in common with terrestrial hurricanes and with the Venus polar vortex. Neptune and other giant planets may also have strong polar vortices.

Dyudina, Ulyana A.; Ingersoll, Andrew P.; Ewald, Shawn P.; Vasavada, Ashwin R.; West, Robert A.; Baines, Kevin H.; Momary, Thomas W.; Del Genio, Anthony D.; Barbara, John M.; Porco, Carolyn C.; Achterberg, Richard K.; Flasar, F. Michael; Simon-Miller, Amy A.; Fletcher, Leigh N.

2009-07-01

59

Saturn's South Polar Vortex Compared to Other Large Vortices in the Solar System  

NASA Astrophysics Data System (ADS)

Observations made by the Imaging Science Subsystem (ISS), Visible and In- frared Mapping Spectrometer (VIMS) and the long-wavelength Composite Infrared Spectrometer (CIRS) aboard the Cassini spacecraft reveal that the large, long-lived cyclonic vortex at Saturn's south pole has a 4200-km-diameter cloud-free nearly circular region. This region has a 4 K warm core extending from the troposphere into the stratosphere, concentric cloud walls extending 20-70 km above the internal clouds, and numerous external clouds whose an- ticyclonic vorticity suggests a convective origin. The rotation speeds of the vortex reach 150-190 m/s, and may strengthen with depth. The Saturn polar vortex has features in common with terrestrial hurricanes and with the Venus polar vortex. Neptune and other giant planets may also have strong polar vortices.

Dyudina, U. A.; Ingersoll, A. P.; Ewald, S. P.; Vasavada, A. R.; West, R. A.; Baines, K. H.; Momary, T. W.; Barbara, J. M.; Del Genio, A. D.; Porco, C. C.; Achterberg, R. K.; Flasar, F.; Simon-Miller, A. A.; Fletcher, L. N.

2008-12-01

60

Production, detection, and manipulation of vortex beams and radially polarized beams  

NASA Astrophysics Data System (ADS)

In this work we describe techniques for the generation of vortex beams, including vortex generating diffraction gratings and diffractive lenses, as well as some possible applications in optical image processing. We then analyze the description of radially polarized beams in terms of superposition of such vortex beams. We present some methods for the production of radially polarized light, that include patterned linear polarizers, specially designed liquid crystal devices and spatial light modulators (SLMs). We analyze the manipulation of this radial polarization by means of wave-plates, in order to obtain other non-standard spatially variant polarized light beams. Theoretical analysis are presented based on the Jones matrix theory, and experimental results are included for all cases.

Moreno, Ignacio; Davis, Jeffrey A.; Cottrell, Don M.

2013-09-01

61

OMAE 1996 -- Proceedings of the 15. international conference on offshore mechanics and arctic engineering. Volume 4: Arctic/polar technology  

SciTech Connect

Volume 4 contains papers on the following topics: arctic/polar technology and development; ice properties; ice engineering; applied ice mechanics; ice-structure interaction; arctic structures and operations; frozen soil properties; and Russian Arctic development. In addition to the regular topics covered in OMAE conferences, there has been a special workshop as part of this year`s conference. In keeping with issues of current interest, there is a workshop on development of oil resources in the Russian Arctic. Over two days, papers dealing with development of oil and gas resources in the Russian Arctic are presented. Volume 4 contains papers from this workshop. Some of the papers have been processed separately for inclusion on the data base.

Nixon, W.A. [ed.] [Univ. of Iowa, Iowa City, IA (United States). Iowa Inst. of Hydraulic Research; Sodhi, D.S. [ed.] [Army Cold Regions Research and Engineering Lab., Hanover, NH (United States); Kennedy, K.P. [ed.] [Canmar/Amoco Canada, Calgary, Alberta (Canada); Yamaguchi, H. [ed.] [Univ. of Tokyo (Japan); Bugno, W. [ed.] [Chevron, San Ramon, CA (United States)

1996-12-01

62

Radiation forces on a Rayleigh particle by highly focused partially coherent and radially polarized vortex beams.  

PubMed

The radiation force of highly focused partially coherent and radially polarized vortex beams on a Rayleigh particle is theoretically studied. The dependence of the radiation force on coherence lengths, beam widths, topological charges of incident vortex beams, and numerical apertures of an objective is analyzed. The transverse scattering force is also investigated. It is found that the azimuthal scattering force can produce torques with respect to the optical axis if the optical tweezers are constructed by the vortex beams carrying orbit angular momentum. The direction of the torque depends on the sign of the topological charge of vortex beams, and the magnitude of the torque increases with the increase of the value of the topological charge. A Rayleigh particle can revolve around the optical axis driven by the vortex beams. PMID:23695323

Shu, Jianhua; Chen, Ziyang; Pu, Jixiong

2013-05-01

63

H2O Isotope Compositions in the Upper Troposphere and Inside the Polar Vortex  

NASA Astrophysics Data System (ADS)

Observations of the isotopic ratio in H2O vapor can provide unique tests of the atmospheric physics that control dehydration. With improved H2O linelists and retrieval methods, we are able to estimate the water isotope abundances in the upper troposphere/lower stratosphere, especially for the tropics, using Fourier Transform InfraRed (FTIR) Interferometer data from the Atmospheric Trace Molecule Spectroscopy (ATMOS) and the MkIV balloon flights. Implications to the troposphere-stratosphere exchange will be discussed. We have also obtained HDO measurements inside of the polar stratospheric vortex. We find that the formation of HDO in the polar vortex is consistent with the production from oxidation of CH3D, just as observed previously for air outside of the polar vortex.

Kuang, Z.; Toon, G. C.; Szeja, S.; Irion, F. W.; Wennberg, P.; Yung, Y. L.

2001-12-01

64

The Arctic polar stratospheric cloud aerosol - Aircraft measurements of reactive nitrogen, total water, and particles  

Microsoft Academic Search

In situ aircraft measurements in the lower stratosphere are used to investigate the reactive nitrogen, NO(y), total water, and particle components of the polar stratospheric cloud (PSC) aerosol in the Arctic. The results are compared to findings from the Antarctic derived using similar measurements and interpretive techniques. The Arctic data show that particle volume well above background values is present

S. R. Kawa; D. W. Fahey; K. K. Kelly; J. E. Dye; D. Baumgardner; B. W. Gandrud; M. Loewenstein; G. V. Ferry; K. R. Chan

1992-01-01

65

The International Arctic Buoy Programme (IABP) - An International Polar Year Every Year  

Microsoft Academic Search

A network of automatic data buoys to monitor synoptic-scale fields of sea level pressure (SLP), surface air temperature (SAT), and ice motion throughout the Arctic Ocean was recommended by the U.S. National Academy of Sciences in 1974. Based on the Academy's recommendation, the Arctic Ocean Buoy Program was established by the Polar Science Center, Applied Physics Laboratory (APL), University of

M. Hanna; I. Rigor; M. Ortmeyer; C. Haas

2004-01-01

66

The January 30, 1989 Arctic polar stratospheric clouds (PSC) event: Evidence for a mechanism of dehydration  

SciTech Connect

In-situ particle measurements made aboard the NASA ER-2 in the Arctic on 890130 (YYMMDD) show Type 1 PSC particles over much of the flight, with instances of embedded Type 2 PSCs. The Type 2 particles were observed at temperatures warmer than the local frost-point temperature of water; extended up to the upper size cutoff of the instrument ({approximately}24 {mu}m diameter); and are shown to contain too large a volume to be primarily NAT. Based on measured vertical temperature profiles, the authors conclude that the Type 2 particles observed on this day were formed above the aircraft in a region where saturation with respect to ice was achieved and were sufficiently large to have fallen into the path of the ER-2. Although, the amount of material in the particles, expressed as water, is small by comparison to the total (vapor + aerosol) water concentration, the flux of water from the falling particles is of sufficient magnitude, if sustained, to lead to dehydration of the source region. These observations verify the mechanism for dehydration of polar vortex air masses by precipitation of ice particles.

Gandrud, B.W.; Dye, J.E.; Baumgardner, D. (NCAR, Boulder, CO (USA)); Ferry, G.V.; Loewenstein, M.; Chan, K.R. (NASA Ames, Moffett Field, CA (USA)); Sanford, L. (Univ. of Washington, Seattle, WA (USA)); Gary, B. (Jet Propulsion Laboratory, Pasadena, CA (USA)); Kelly, K. (NOAA Aeronomy Laboratory, Boulder, CO (USA))

1990-03-01

67

Computations of diabatic descent in the stratospheric polar vortex  

Microsoft Academic Search

A radiation model, together with National Meteorological Center temperature observations, was used to compute daily net heating rates in the northern hemisphere (NH) for the Arctic late fall and winter periods of both 1988-1989 and 1991-1992 and in the southern hemisphere (SH) for the Antarctic fall and winters of 1987 and 1992. The heating rates were interpolated to potential temperature

Joan E. Rosenfield; Paul A. Newman; Mark R. Schoeberl

1994-01-01

68

Development and testing of Polar Weather Research and Forecasting model: 2. Arctic Ocean  

Microsoft Academic Search

A version of the state-of-the-art Weather Research and Forecasting model (WRF) has been developed for polar applications. The model known as “Polar WRF” is tested over the Arctic Ocean with a western Arctic grid using 25-km resolution. The model is based upon WRF version 2.2, with improvements to the Noah land surface model and the snowpack treatment. The ocean surface

David H. Bromwich; Keith M. Hines; Le-Sheng Bai

2009-01-01

69

Arctic Ozone Loss in Threshold Conditions: Match Observations in 1997/1998 and 1998/1999.  

National Technical Information Service (NTIS)

Chemical ozone loss rates inside the Arctic polar vortex were determined in early 1998 and early 1999 by using the Match technique based on coordinated ozone sonde measurements. These two winters provide the only opportunities in recent years to investiga...

A. Schultz E. Reimer G. O. Braathen M. Rex N. R. Harris

2001-01-01

70

Potential Vorticity and Mixing in the South Polar Vortex During Spring  

Microsoft Academic Search

A central part of the explanation of the Antarctic ozone hole is the dynamical isolation provided by the intense vortex present over the south polar region until late in the spring. In this paper some fluid dynamical aspects of the Antarctic ozone hole phenomena are investigated, using data collected by the ER-2 aircraft during the Airborne Antarctic Ozone Experiment (AAOE).

D. L. Hartmann; K. R. Chan; B. L. Gary; M. R. Schoeberl; P. A. Newman; R. L. Martin; M. Loewenstein; J. R. Podolske; S. E. Strahan

1989-01-01

71

Descent of long-lived trace gases in the water polar vortex  

Microsoft Academic Search

Recent observations of CH4 and HF from the UARS Halogen Limb Occulation Experiment (HALOE) suggest that vigorous descent occurs within the polar winter vortex with ``mesospheric'' values of CH4 evident down to 30 mbar. This study shows that a highly accurate two-dimensional model advection scheme coupled with a modern radiation scheme, parameterized planetary and gravity wave drag algorithms can produce

Julio T. Bacmeister; Mark R. Schoeberl; Michael E. Summers; Joan R. Rosenfield; Xun Zhu

1995-01-01

72

Observations of backscatter, particle concentration and frost point in north polar vortex stratospheric clouds  

SciTech Connect

Near-simultaneous soundings of backscatter, particle size distribution and frost point were obtained in north polar stratospheric clouds (PSCs) near the center of the vortex. The measured particle sizes and concentration in type I PSCs tend to confirm earlier predictions based on remotely sensed properties.

Rosen, J.M.; Kjome, N.T. (Univ. of Wyoming, Laramie (USA)); Oltmans, S.J. (NOAA CMDL, Boulder, CO (USA))

1990-08-01

73

Polar vortex evolution during the 2002 Antarctic major warming as observed by the Odin satellite  

NASA Astrophysics Data System (ADS)

In September 2002 the Antarctic polar vortex split in two under the influence of a sudden warming. During this event, the Odin satellite was able to measure both ozone (O3) and chlorine monoxide (ClO), a key constituent responsible for the so-called "ozone hole", together with nitrous oxide (N2O), a dynamical tracer, and nitric acid (HNO3) and nitrogen dioxide (NO2), tracers of denitrification. The submillimeter radiometer (SMR) microwave instrument and the Optical Spectrograph and Infrared Imager System (OSIRIS) UV-visible light spectrometer (VIS) and IR instrument on board Odin have sounded the polar vortex during three different periods: before (19-20 September), during (24-25 September), and after (1-2 and 4-5 October) the vortex split. Odin observations coupled with the Reactive Processes Ruling the Ozone Budget in the Stratosphere (REPROBUS) chemical transport model at and above 500 K isentropic surfaces (heights above 18 km) reveal that on 19-20 September the Antarctic vortex was dynamically stable and chemically nominal: denitrified, with a nearly complete chlorine activation, and a 70% O3 loss at 500 K. On 25-26 September the unusual morphology of the vortex is monitored by the N2O observations. The measured ClO decay is consistent with other observations performed in 2002 and in the past. The vortex split episode is followed by a nearly complete deactivation of the ClO radicals on 1-2 October, leading to the end of the chemical O3 loss, while HNO3 and NO2 fields start increasing. This acceleration of the chlorine deactivation results from the warming of the Antarctic vortex in 2002, putting an early end to the polar stratospheric cloud season. The model simulation suggests that the vortex elongation toward regions of strong solar irradiance also favored the rapid reformation of ClONO2. The observed dynamical and chemical evolution of the 2002 polar vortex is qualitatively well reproduced by REPROBUS. Quantitative differences are mainly attributable to the too weak amounts of HNO3 in the model, which do not produce enough NO2 in presence of sunlight to deactivate chlorine as fast as observed by Odin.

Ricaud, P.; LefèVre, F.; Berthet, G.; Murtagh, D.; Llewellyn, E. J.; MéGie, G.; KyröLä, E.; Leppelmeier, G. W.; Auvinen, H.; Boonne, C.; Brohede, S.; Degenstein, D. A.; de La Noë, J.; Dupuy, E.; El Amraoui, L.; Eriksson, P.; Evans, W. F. J.; Frisk, U.; Gattinger, R. L.; Girod, F.; Haley, C. S.; Hassinen, S.; Hauchecorne, A.; Jimenez, C.; Kyrö, E.; Lautié, N.; Le FlochmoëN, E.; Lloyd, N. D.; McConnell, J. C.; McDade, I. C.; Nordh, L.; Olberg, M.; Pazmino, A.; Petelina, S. V.; Sandqvist, A.; SeppäLä, A.; Sioris, C. E.; Solheim, B. H.; Stegman, J.; Strong, K.; Taalas, P.; Urban, J.; von Savigny, C.; von Scheele, F.; Witt, G.

2005-03-01

74

Possible Effects of Climate Warming on Selected Populations of Polar Bears (Ursus maritimus) in the Canadian Arctic  

Microsoft Academic Search

Polar bears depend on sea ice for survival. Climate warming in the Arctic has caused significant declines in total cover and thickness of sea ice in the polar basin and progressively earlier breakup in some areas. Inuit hunters in the areas of four polar bear populations in the eastern Canadian Arctic (including Western Hudson Bay) have reported seeing more bears

IAN STIRLING; CLAIRE L. PARKINSON

2006-01-01

75

Stratospheric ClONO2 and HNO3 profiles inside the Arctic vortex from MIPAS-B limb emission spectra obtained during EASOE  

Microsoft Academic Search

Vertical profiles of ClONO2 and HNO3 inside the Arctic vortex have been retrieved from infrared limb emission spectra recorded during balloon flights on January 13 and in the night of March 14\\/15, 1992 from Esrange, Sweden (68°N) as part of the European Arctic Stratospheric Ozone Experiment (EASOE). The instrumentation used was the cryogenic Michelson Interferometer for Passive Atmospheric Sounding, Balloon-borne

H. Oelhaf; T. v. Clarmann; H. Fischer; F. Friedl-Vallon; Ch. Fritzsche; A. Linden; Ch. Piesch; M. Seefeldner; W. Völker

1994-01-01

76

Spatial, temporal, and vertical variability of polar stratospheric ozone loss in the Arctic winters 2004/05-2009/10  

NASA Astrophysics Data System (ADS)

The stratospheric ozone loss during the Arctic winters 2004/05-2009/10 is investigated by using high resolution simulations from the chemical transport model Mimosa-Chim and observations from Microwave Limb Sounder (MLS) on Aura by the passive tracer technique. The winter 2004/05 was the coldest of the series with strongest chlorine activation. The ozone loss diagnosed from both model and measurements inside the polar vortex at 475 K ranges from ~1-0.7 ppmv in the warm winter 2005/06 to 1.7 ppmv in the cold winter 2004/05. Halogenated (chlorine and bromine) catalytic cycles contribute to 75-90% of the accumulated ozone loss at this level. At 675 K the lowest loss of ~0.4 ppmv is computed in 2008/09 from both simulations and observations and, the highest loss is estimated in 2006/07 by the model (1.3 ppmv) and in 2004/05 by MLS (1.5 ppmv). Most of the ozone loss (60-75%) at this level results from cycles catalysed by nitrogen oxides (NO and NO2) rather than halogens. At both 475 and 675 K levels the simulated ozone evolution inside the polar vortex is in reasonably good agreement with the observations. The ozone total column loss deduced from the model calculations at the MLS sampling locations inside the vortex ranges between 40 DU in 2005/06 and 94 DU in 2004/05, while that derived from observations ranges between 37 DU and 111 DU in the same winters. These estimates from both Mimosa-Chim and MLS are in general good agreement with those from the ground-based UV-VIS (ultra violet-visible) ozone loss analyses for the respective winters.

Kuttippurath, J.; Godin-Beekmann, S.; Lefèvre, F.; Goutail, F.

2010-06-01

77

The polar mesospheric cloud mass in the Arctic summer  

NASA Astrophysics Data System (ADS)

We infer the polar mesospheric cloud (PMC) mass throughout the Arctic summer using results from two sets of satellite observations and a microphysical model. Solar backscatter ultraviolet (SBUV) PMC observations in July 1999 indicate a burst of activity persisting for ˜8 days after a space shuttle launch and averaging 262 ± 52 t near 4.7 local time. This mass is consistent with the propellant mass available from the shuttle's main engines and accounts for 22% of the total SBUV PMC mass over the season between 65° and 75°N. This is the first evidence that PMCs formed by space shuttle water exhaust can contribute significantly to both the number of observed PMCs and the total PMC mass in a season. In another approach, 11 years of observations by the Halogen Occultation Experiment (HALOE) indicate that on average 90 ± 12 t of water ice is present near local midnight between 65° and 75°N. Using simultaneous HALOE water vapor observations, we find that a one-dimensional microphysical model reproduces the start and end of the PMC season but overpredicts the ice mass by about a factor of 1.8 when compared with the observations. This overprediction is within the time-dependent variability of ice formation and the uncertainties of temperature, water vapor, and vertical winds used to initialize the model.

Stevens, Michael H.; Englert, Christoph R.; Deland, Matthew T.; Hervig, Mark

2005-02-01

78

Spatial Correlation Properties of Tightly Focused J0-Correlated Azimuthally Polarized Vortex Beams  

NASA Astrophysics Data System (ADS)

Based on vectorial Debye diffraction theory, the spatial correlation properties in the focal region of a J0-correlated azimuthally polarized vortex beam through a high numerical aperture (NA) are analyzed. The expressions for a pair of points on the axis of symmetry and for a pair of points in the focal plane are derived. It is found that the longitudinal and transverse coherence lengths in the focal region change with the variation in the topological charge and coherence parameter of the vortex field, together with the NA values. In addition, the degree of coherence is shown to possess phase singularities.

Rao, Lian-Zhou; Lin, Hui-Chuan; Sun, Qing-Quan

2013-05-01

79

Chlorine chemistry on polar stratospheric cloud particles in the Arctic winter  

Microsoft Academic Search

Simultaneous in situ measurements of hydrochloric acid (HCl) and chlorine monoxide (ClO) in the Arctic winter vortex showed large HCl losses, of up to 1 part per billion by volume (ppbv), which were correlated with high ClO levels of up to 1.4 ppbv. Air parcel trajectory analysis identified that this conversion of inorganic chlorine occurred at air temperatures of less

C. R. Webster; R. D. May; D. W. Toohey; L. M. Avallone; J. G. Anderson; P. Newman; L. Lait; M. R. Schoeberl; J. W. Elkins; K. R. Chan

1993-01-01

80

Development and testing of Polar Weather Research and Forecasting model: 2. Arctic Ocean  

NASA Astrophysics Data System (ADS)

A version of the state-of-the-art Weather Research and Forecasting model (WRF) has been developed for polar applications. The model known as "Polar WRF" is tested over the Arctic Ocean with a western Arctic grid using 25-km resolution. The model is based upon WRF version 2.2, with improvements to the Noah land surface model and the snowpack treatment. The ocean surface treatment is modified to include fractional sea ice. Simulations consist of a series of 48-h integrations initialized daily at 0000 UTC. The initial 24 h are taken as model spin-up time for the atmospheric hydrology and boundary layer processes. Arctic conditions are simulated for the selected months: January 1998, June 1998, and August 1998 representing midwinter, early summer, and late summer conditions, respectively, from the Surface Heat Budget of the Arctic (SHEBA) study. The albedo of sea ice is specified as a function of time and latitude for June and as a function of time for August. Simulation results are compared with observations of the drifting ice station SHEBA in the Arctic ice pack. Polar WRF simulations show good agreement with observations for all three months. Some differences between the simulations and observation occur owing to apparent errors in the synoptic forecasts and the representation of clouds. Nevertheless, the biases in the simulated fields appear to be small, and Polar WRF appears to be a very good tool for studies of Arctic Ocean meteorology.

Bromwich, David H.; Hines, Keith M.; Bai, Le-Sheng

2009-04-01

81

Relation between 300-mb North Polar Vortex and Equatorial SST, QBO, and Sunspot Number and the Record Contraction of the Vortex in 1988-89.  

NASA Astrophysics Data System (ADS)

The size of the 300-mb north circumpolar vortex and quadrants has been estimated between 1963 and 1989 by planimetering the area poleward of contours in the main belt of westerlies on the 300-mb mean-monthly polar-stereographic maps analyzed by the Meteorological Institute, Free University of Berlin. The annual-mean vortex was most contracted in 1989, 6.4% less than average size, and next most contracted in 1988, 4.6% less than average size. There have been three extensive vortex displacements during this period, the last toward the North Pacific and associated with the strong El Niño of 1982-83.Based on 108 seasonal deviations, there has been a significant correlation of 0.39 between sea surface temperature (SST) in the eastern equatorial Pacific and vortex size three seasons later, that is, the vortex has tended to be contracted following El Niño. There has been a highly significant correlation of 0.45 between this SST and the size of quadrant 90°W-180° in the same season, that is, this `El Niño' quadrant has tended to be expanded at the time of El Niño.The correlation of 0.29 between the 50-mb zonal wind at Singapore and vortex size one season later (contracted vortex in the west-wind phase of the stratospheric equatorial QBO) is not significant. There is better evidence for contraction of the vortex in the west-wind phase of the QBO when the sunspot number is relatively high.

Angell, J. K.

1992-01-01

82

Polarization-selective vortex-core switching by tailored orthogonal Gaussian-pulse currents  

SciTech Connect

We experimentally demonstrate low-power-consumption vortex-core switching in magnetic nanodisks using tailored rotating magnetic fields produced with orthogonal and unipolar Gaussian-pulse currents. The optimal width of the orthogonal pulses and their time delay are found, from analytical and micromagnetic numerical calculations, to be determined only by the angular eigenfrequency {omega}{sub D} for a given vortex-state disk of polarization p, such that {sigma}=1/{omega}{sub D} and ?{Delta}t={pi}/2 p/{omega}{sub D} . The estimated optimal pulse parameters are in good agreement with the experimental results. This work lays a foundation for energy-efficient information recording in vortex-core cross-point architecture.

Jung, H.; Choi, Y. -S.; Yoo, M. -W.; Im, M. -Y.; Kim, S. -K.

2010-10-13

83

A quasi-Lagrangian coordinate system based on high resolution tracer observations: implementation for the Antarctic polar vortex  

NASA Astrophysics Data System (ADS)

In order to quantitatively analyse the chemical and dynamical evolution of the polar vortex it has proven extremely useful to work with coordinate systems that follow the vortex flow. We propose here a two-dimensional quasi-Lagrangian coordinate system {?i, ??i}, based on the mixing ratio of a long-lived stratospheric trace gas i, and its systematic use with i = N2O, in order to describe the structure of a well-developed Antarctic polar vortex. In the coordinate system {?i, ??i} the mixing ratio ?i is the vertical coordinate and ??i = ?i(?)-?ivort(?) is the meridional coordinate (?ivort(?) being a vertical reference profile in the vortex core). The quasi-Lagrangian coordinates {?i, ??i} persist for much longer time than standard isentropic coordinates, potential temperature ? and equivalent latitude ?e, do not require explicit reference to geographic space, and can be derived directly from high-resolution in situ measurements. They are therefore well-suited for studying the evolution of the Antarctic polar vortex throughout the polar winter with respect to the relevant chemical and microphysical processes. By using the introduced coordinate system {?N2O, ??N2O} we analyze the well-developed Antarctic vortex investigated during the APE-GAIA (Airborne Polar Experiment - Geophysica Aircraft in Antarctica - 1999) campaign (Carli et al., 2000). A criterion, which uses the local in-situ measurements of ?i=?i(?) and attributes the inner vortex edge to a rapid change (?-step) in the meridional profile of the mixing ratio ?i, is developed to determine the (Antarctic) inner vortex edge. In turn, we suggest that the outer vortex edge of a well-developed Antarctic vortex can be attributed to the position of a local minimum of the ?H2O gradient in the polar vortex area. For a well-developed Antarctic vortex, the ??N2O-parametrization of tracer-tracer relationships allows to distinguish the tracer inter-relationships in the vortex core, vortex boundary region and surf zone and to examine their meridional variation throughout these regions. This is illustrated by analyzing the tracer-tracer relationships ?i : ?N2O obtained from the in-situ data of the APE-GAIA campaign for i = CFC-11, CFC-12, H-1211 and SF6. A number of solitary anomalous points in the CFC-11 : N2O correlation, observed in the Antarctic vortex core, are interpreted in terms of small-scale cross-isentropic dispersion.

Ivanova, E. V.; Volk, C. M.; Riediger, O.; Klein, H.; Sitnikov, N. M.; Ulanovskii, A. E.; Yushkov, V. A.; Ravegnani, F.; Möbius, T.; Schmidt, U.

2008-08-01

84

Increased UV radiation due to polar ozone chemical depletion and vortex occurrences at southern sub-polar latitudes in the period (1997-2005)  

Microsoft Academic Search

The variability of total ozone and UV radiation from Total Ozone Mapping Spectrometer (TOMS) measurements is analyzed as a function of polar vortex occurrences over the southern subpolar regions during the 1997-2005 period. The analysis of vortex occurrences showed high interannual variability in the 40° S-60° S latitude band with a longitudinal asymmetry showing the largest frequencies over the 90°

A. F. Pazmino; S. Godin-Beekmann; E. A. Luccini; R. D. Piacentini; E. J. Quel; A. Hauchecorne

2008-01-01

85

Increased UV radiation due to polar ozone chemical depletion and vortex occurrences at southern sub-polar latitudes in the period (1997–2005)  

Microsoft Academic Search

The variability of total ozone and UV radiation from To- tal Ozone Mapping Spectrometer (TOMS) measurements is analyzed as a function of polar vortex occurrences over the southern subpolar regions during the 1997-2005 period. The analysis of vortex occurrences showed high interannual vari- ability in the 40 S-60 S latitude band with a longitudinal asymmetry showing the largest frequencies over

A. F. Pazmi; S. Godin-Beekmann; E. A. Luccini; R. D. Piacentini; E. J. Quel; A. Hauchecorne

2008-01-01

86

Magnetic vortex oscillator driven by d.c. spin-polarized current  

NASA Astrophysics Data System (ADS)

Transfer of angular momentum from a spin-polarized current to a ferromagnet provides an efficient means to control the magnetization dynamics of nanomagnets. A peculiar consequence of this spin torque, the ability to induce persistent oscillations in a nanomagnet by applying a d.c. current, has previously been reported only for spatially uniform nanomagnets. Here, we demonstrate that a quintessentially non-uniform magnetic structure, a magnetic vortex, isolated within a nanoscale spin-valve structure, can be excited into persistent microwave-frequency oscillations by a spin-polarized d.c. current. Comparison with micromagnetic simulations leads to identification of the oscillations with a precession of the vortex core. The oscillations, which can be obtained in essentially zero magnetic field, exhibit linewidths that can be narrower than 300kHz at ~1.1GHz, making these highly compact spin-torque vortex-oscillator devices potential candidates for microwave signal-processing applications, and a powerful new tool for fundamental studies of vortex dynamics in magnetic nanostructures.

Pribiag, V. S.; Krivorotov, I. N.; Fuchs, G. D.; Braganca, P. M.; Ozatay, O.; Sankey, J. C.; Ralph, D. C.; Buhrman, R. A.

2007-07-01

87

Vortex  

NSDL National Science Digital Library

In this activity, learners create a tornado in a bottle to observe a spiraling, funnel-shaped vortex. A simple connector device allows water to drain from a 2-liter bottle into a second bottle. Learners can observe the whirling water and then repeat the process by inverting the bottle. Use this activity to talk about surface tension, pressure, gravity, friction, angular momentum, and centripetal force.

Exploratorium, The

2012-06-26

88

Sustained Arctic Observations: A Legacy of the Polar Year  

NASA Astrophysics Data System (ADS)

Is the Arctic a vast, beautiful, wild, and unsullied natural refuge, or is it small, fragile, and vulnerable, suffering the brunt of global warming? In the late nineteenth century, as U.S. admiral Robert E. Peary and his competitors engaged in their mad scramble to be the first humans to set foot on the North Pole, ``fragile'' was unlikely to be an adjective that sprang to mind when they described their surroundings. Quite the opposite, exploring the Arctic exposed the fragility of man. But the Arctic Ocean and mankind's relationships to it are changing fast.

Alverson, Keith

2008-09-01

89

Observational evidence of the delayed response of stratospheric polar vortex variability to ENSO SST anomalies  

Microsoft Academic Search

The temporal and spatial relationship between ENSO and the extratropical stratospheric variability in the Northern Hemisphere\\u000a is examined. In general, there exists a negative correlation between ENSO and the strength of the polar vortex, but the maximum\\u000a correlation is found in the next winter season after the mature phase of ENSO event, rather than in the concurrent winter.\\u000a Specifically, the

R.-C. RenMing; Ming Cai; Chunyi Xiang; Guoxiong Wu

2011-01-01

90

Polar bear and walrus response to the rapid decline in Arctic sea ice  

USGS Publications Warehouse

The Arctic is warming faster than other regions of the world due to positive climate feedbacks associated with loss of snow and ice. One highly visible consequence has been a rapid decline in Arctic sea ice over the past 3 decades - a decline projected to continue and result in ice-free summers likely as soon as 2030. The polar bear (Ursus maritimus) and the Pacific walrus (Odobenus rosmarus divergens) are dependent on sea ice over the continental shelves of the Arctic Ocean's marginal seas. The continental shelves are shallow regions with high biological productivity, supporting abundant marine life within the water column and on the sea floor. Polar bears use sea ice as a platform for hunting ice seals; walruses use sea ice as a resting platform between dives to forage for clams and other bottom-dwelling invertebrates. How have sea ice changes affected polar bears and walruses? How will anticipated changes affect them in the future?

Oakley, K.; Whalen, M.; Douglas, D.; Udevitz, M.; Atwood, T.; Jay, C.

2012-01-01

91

Polar vortex dynamics observed by means of stratospheric and mesospheric CO ground-based measurements carried out at Thule (76.5°N, 68.8°W), Greenland  

NASA Astrophysics Data System (ADS)

The distribution of carbon monoxide (CO) in the stratosphere and mesosphere is a useful tool to study middle atmospheric dynamical processes during polar winters. CO concentrations exhibit a strong latitudinal gradient (positive moving towards the winter pole) and a large vertical increase in the mesosphere and lower thermosphere. These large gradients, together with a long photochemical lifetime, make CO an excellent tracer for studying both the poleward transport of air masses from lower latitudes and the descent of air inside the polar vortex. The CO measurements used in this study have been obtained observing the 230 GHz transition by means of a Ground-Based Millimeter-wave Spectrometer (GBMS) with a pass band of 50 MHz and a spectral resolution of 65 kHz. The GBMS was designed and built at the State University of New York at Stony Brook in the early 90's to detect rotational emission spectra of middle atmospheric trace gases at frequencies between approximately 230 and 280 GHz. Since the shape of spectral lines at millimeter-wave frequencies strongly depends on the pressure line broadening, an implementation of the Optimal Estimation technique allows the retrieval of mixing ratio vertical profiles from emission spectra. The GBMS spectral coverage and resolution allows CO mixing ratio profiles to be retrieved between about 30 and 80 km, i.e., at an altitude range where other forms of data used in dynamical studies become increasingly sparse or absent. In January 2009, the GBMS was installed at the NDACC (Network for the Detection of Atmospheric Composition Change) Arctic station at Thule (76.5°N, 68.8°W), Greenland, to commence a long-term observation plan of the polar middle atmosphere. Three winter campaigns have been carried out since then (winters 2008/09, 2009/10, and 2010/11), and the 2011/2012 campaign has been funded and it is about to get started. In this contribution, 4 winters of GBMS CO observations will be presented. Owing to the time span of the GBMS data record and the high temporal resolution of its spectral measurements (15 minutes), the GBMS CO vertical profiles allow to capture both the interannual variability of subsidence rates of air masses inside the polar vortex as well as the short-term planetary wave activity observed near the edge of the polar vortex. Particular emphasis is given to the two record winters of 2008/09 and 2010/11, characterized by opposite extreme events: the most intense Sudden Stratospheric Warming (2008/09) and the most severe Arctic ozone depletion ever observed (2010/11).

Fiorucci, I.; Muscari, G.; Bertagnolio, P. P.; Di Biagio, C.; Eriksen, P.; de Zafra, R. L.

2012-04-01

92

Spatial, temporal, and vertical variability of polar stratospheric ozone loss in the Arctic winters 2004/2005-2009/2010  

NASA Astrophysics Data System (ADS)

The polar stratospheric ozone loss during the Arctic winters 2004/2005-2009/2010 is investigated by using high resolution simulations from the chemical transport model Mimosa-Chim and observations from Aura Microwave Limb Sounder (MLS), by applying the passive tracer technique. The winter 2004/2005 shows the coldest temperatures, highest area of polar stratospheric clouds and strongest chlorine activation in 2004/2005-2009/2010. The ozone loss diagnosed from both simulations and measurements inside the polar vortex at 475 K ranges from 0.7 ppmv in the warm winter 2005/2006 to 1.5-1.7 ppmv in the cold winter 2004/2005. Halogenated (chlorine and bromine) catalytic cycles contribute to 75-90% of the ozone loss at this level. At 675 K the lowest loss of 0.3-0.5 ppmv is computed in 2008/2009, and the highest loss of 1.3 ppmv is estimated in 2006/2007 by the model and in 2004/2005 by MLS. Most of the ozone loss (60-75%) at this level results from nitrogen catalytic cycles rather than halogen cycles. At both 475 and 675 K levels the simulated ozone and ozone loss evolution inside the vortex is in reasonably good agreement with the MLS observations. The ozone partial column loss in 350-850 K deduced from the model calculations at the MLS sampling locations inside the polar vortex ranges between 43 DU in 2005/2006 and 109 DU in 2004/2005, while those derived from the MLS observations range between 26 DU and 115 DU for the same winters. The partial column ozone depletion derived in that vertical range is larger than that estimated in 350-550 K by 19±7 DU on average, mainly due to NOx chemistry. The column ozone loss estimates from both Mimosa-Chim and MLS in 350-850 K are generally in good agreement with those derived from ground-based ultraviolet-visible spectrometer total ozone observations for the respective winters, except in 2010.

Kuttippurath, J.; Godin-Beekmann, S.; Lefèvre, F.; Goutail, F.

2010-10-01

93

Generation of high-order polarized vortex beam by achromatic meniscus axicon doublet  

NASA Astrophysics Data System (ADS)

A method for generating a high-order (?2) polarized vortex beam by using achromatic meniscus axicon doublets (MADs) is described. The MAD has a rotationally symmetric structure and consists of a pair of identical meniscus axicons with the same apex angle. It exploits four total internal reflections when collimated rays pass through it to produce a half-wave retardation, but with azimuth-variant polarization orientations. The characteristics of high achromatism of retardance, reasonable acceptance angular aperture for MAD, are numerically demonstrated. The effect of the remaining stress birefringence of optical materials on retardation is also discussed.

Zhang, Xusheng; Qiu, Lirong

2013-08-01

94

Polar bear maternal den habitat in the Arctic National Wildlife Refuge, Alaska  

USGS Publications Warehouse

Polar bears (Ursus maritimus) give birth during mid-winter in dens of ice and snow. Denning polar bears subjected to human disturbances may abandon dens before their altricial young can survive the rigors of the Arctic winter. Because the Arctic coastal plain of Alaska is an area of high petroleum potential and contains existing and planned oil field developments, the distribution of polar bear dens on the plain is of interest to land managers. Therefore, as part of a study of denning habitats along the entire Arctic coast of Alaska, we examined high-resolution aerial photographs (n = 1655) of the 7994 km2 coastal plain included in the Arctic National Wildlife Refuge (ANWR) and mapped 3621 km of bank habitat suitable for denning by polar bears. Such habitats were distributed uniformly and comprised 0.29% (23.2 km2) of the coastal plain between the Canning River and the Canadian border. Ground-truth sampling suggested that we had correctly identified 91.5% of bank denning habitats on the ANWR coastal plain. Knowledge of the distribution of these habitats will help facilitate informed management of human activities and minimize disruption of polar bears in maternal dens.

Durner, G. M.; Amstrup, S. C.; Ambrosius, K. J.

2006-01-01

95

Spatial variation of ozone depletion rates in the springtime Antarctic polar vortex.  

PubMed

An area-mapping technique, designed to filter out synoptic perturbations of the Antarctic polar vortex such as distortion or displacement away from the pole, was applied to the Nimbus-7 TOMS (Total Ozone Mapping Spectrometer) data. This procedure reveals the detailed morphology of the temporal evolution of column O3. The results for the austral spring of 1987 suggest the existence of a relatively stable collar region enclosing an interior that is undergoing large variations. There is tentative evidence for quasi-periodic (15 to 20 days) O3 fluctuations in the collar and for upwelling of tropospheric air in late spring. A simplified photochemical model of O3 loss and the temporal evolution of the area-mapped polar O3 are used to constrain the chlorine monoxide (ClO) concentrations in the springtime Antarctic vortex. The concentrations required to account for the observed loss of O3 are higher than those previously reported by Anderson et al. but are comparable to their recently revised values. However, the O3 loss rates could be larger than deduced here because of underestimates of total O3 by TOMS near the terminator. This uncertainty, together with the uncertainties associated with measurements acquired during the Airborne Antarctic Ozone Experiment, suggests that in early spring, closer to the vortex center, there may be even larger ClO concentrations than have yet been detected. PMID:11538181

Yung, Y L; Allen, M; Crisp, D; Zurek, R W; Sander, S P

1990-05-11

96

Airborne measurements during the European Arctic Stratospheric Ozone Experiment: Observation of OClO  

SciTech Connect

This article reports on aircraft based measurements of column OClO densities over the arctic region, both inside and outside the polar vortex between December 1991, and March 1992. The largest amounts were always observed near the vortex interior. This molecule is conceived as a product of photochemical reactions of ClO and BrO, leading to ozone destruction.

Brandtjen, R.; Kluepfel, T.; Perner, D. (Max-Planck-Institut fuer Chemie, Mainz (Germany)); Knudsen, B.M. (Danish Meteorological Institute, Copenhagen (Denmark))

1994-06-22

97

Growth and variation in the bacula of polar bears (Ursus maritimus) in the Canadian Arctic  

Microsoft Academic Search

Structure and growth of the baculum (os penis) in arctoid carnivores have been well described for many species. This study presents the first extensive analysis of bacular growth and variation for bears (Ursidae), based on 871 bacula of polar bears Ursus maritimus (858 of known age) that were shot in the Canadian Arctic from 1994 to 1997. Bacular length, maximal

Markus G. Dyck; Jackie M. Bourgeois; Edward H. Miller

2004-01-01

98

3. Observing the Arctic from space: educational opportunities for an International Polar Year  

Microsoft Academic Search

Recommendations for an International Polar Year (IPY) will require integrated circumpolar research projects using present and advanced technologies. The IPY will offer exceptional opportunities for participation by indigenous residents of the Arctic. Educational outreach will be an essential component of IPY programs, to improve science competence and citizen awareness through participation in IPY projects and utilization of educational products. An

J. Kelley; G. Yanow; V. Alexander; L. Johnson

2003-01-01

99

Observing the Arctic From Space: Educational Opportunities for an International Polar Year  

Microsoft Academic Search

Recommendations for an International Polar Year (IPY) will require integrated circumpolar research projects using present and advanced technologies. The IPY will offer exceptional opportunities for participation by indigenous residents of the Arctic. Educational outreach will be an essential component of IPY programs, to improve science competence and citizen awareness through participation in IPY projects and utilization of educational products. An

J. J. Kelley; G. Yanow; V. Alexander; L. Johnson

2003-01-01

100

A hole in the Arctic polar ozone layer during March 1986  

Microsoft Academic Search

A craterlike structure or hole in the Arctic polar ozone layer during March 1986 has been observed in the total ozone images from the total ozone mapping spectrometer instrument on the Nimbus 7 satellite. Observations from ozonesondes in the vicinity of this crater show a depleted region in the altitude profile from 10 to 16 km. This altitude region of

W. F. J. Evans

1989-01-01

101

Arctic Research and Writing: A Lasting Legacy of the International Polar Year  

ERIC Educational Resources Information Center

|Recently, senior-level physics students joined thousands of scientists from over 60 nations to examine a wide range of physical, biological, and social research topics as part of the International Polar Year (IPY). Through a National Science Foundation (NSF)-funded research project, these students applied physics concepts to the study of Arctic

Englert, Karl; Coon, Brian; Hinckley, Matt; Pruis, Matt

2009-01-01

102

A closer look at Arctic ozone loss and polar stratospheric clouds  

Microsoft Academic Search

The empirical relationship found between column-integrated Arctic ozone loss and the volume of polar stratospheric clouds inferred from meteorological analyses is updated and examined in more detail. The relationship is found to hold at different altitudes as well as in the column. Analysis of the photochemistry leading to the ozone loss shows that the early winter activation is limited by

N. R. P. Harris; R. Lehmann; M. Rex; P. von der Gathen

2010-01-01

103

A closer look at Arctic ozone loss and polar stratospheric clouds  

Microsoft Academic Search

The empirical relationship found between column-integrated Arctic ozone loss and the potential vol- ume of polar stratospheric clouds inferred from meteorolog- ical analyses is recalculated in a self-consistent manner us- ing the ERA Interim reanalyses. The relationship is found to hold at different altitudes as well as in the column. The use of a PSC formation threshold based on temperature

N. R. P. Harris; R. Lehmann; M. Rex; P. von der Gathen

2010-01-01

104

A closer look at Arctic ozone loss and polar stratospheric clouds  

Microsoft Academic Search

The empirical relationship found between column-integrated Arctic ozone loss and the potential volume of polar stratospheric clouds inferred from meteorological analyses is recalculated in a self-consistent manner using the ERA Interim reanalyses. The relationship is found to hold at different altitudes as well as in the column. The use of a PSC formation threshold based on temperature dependent cold aerosol

N. R. P. Harris; R. Lehmann; M. Rex; P. von der Gathen

2010-01-01

105

Arctic Research and Writing: A Lasting Legacy of the International Polar Year  

ERIC Educational Resources Information Center

Recently, senior-level physics students joined thousands of scientists from over 60 nations to examine a wide range of physical, biological, and social research topics as part of the International Polar Year (IPY). Through a National Science Foundation (NSF)-funded research project, these students applied physics concepts to the study of Arctic

Englert, Karl; Coon, Brian; Hinckley, Matt; Pruis, Matt

2009-01-01

106

Bacterial diversity in faeces from polar bear (Ursus maritimus) in Arctic Svalbard  

Microsoft Academic Search

BACKGROUND: Polar bears (Ursus maritimus) are major predators in the Arctic marine ecosystem, feeding mainly on seals, and living closely associated with sea ice. Little is known of their gut microbial ecology and the main purpose of this study was to investigate the microbial diversity in faeces of polar bears in Svalbard, Norway (74-81°N, 10-33°E). In addition the level of

Trine Glad; Pål Bernhardsen; Kaare M Nielsen; Lorenzo Brusetti; Magnus Andersen; Jon Aars; Monica A Sundset

2010-01-01

107

Polarity reversal of a magnetic vortex core by a unipolar, non-resonant in-plane pulsed magnetic field.  

SciTech Connect

We report the polarity reversal of a magnetic vortex core using a nonresonant in-plane pulsed magnetic field of arbitrary waveform studied using time-resolved x-ray photoemission electron microscopy and micromagnetic simulations. The imaging and simulations show that a 5 mT pulse, higher than the critical field for nonlinear effects, effectively leads to the randomization of the vortex core polarity. The micromagnetic simulations further show that the onset of stochastic core polarity randomization does not necessarily coincide with the critical reversal field, leading to a field window for predictable core reversal.

Keavney, D. J.; Cheng, X. M.; Buchanan, K. S. (Center for Nanoscale Materials); ( XSD); (Colorado State Univ.)

2009-06-24

108

Quantification of the transport of chemical constituents from the polar vortex to midlatitudes in the lower stratosphere using the high-resolution advection model MIMOSA and effective diffusivity  

NASA Astrophysics Data System (ADS)

The observed decrease of ozone in the northern midlatitude lower stratosphere is only partially reproduced by chemical models. The transport of ozone-depleted air from the polar vortex is one of the proposed mechanisms to explain the discrepancy. Here we present a study on the quantification of the air mass transported from the polar vortex to midlatitude during the four winters 1996-1997 to 1999-2000, in relation with vortex filamentation and break up, using the high-resolution advection model MIMOSA on isentropic surfaces. Sensitivity tests show that the advection model is able to predict the location of polar filaments with accuracy better than 100 km, limited by uncertainties in meteorological advecting wind fields. The effective diffusivity diagnostic is used to evaluate the intensity of the vortex edge barrier and to quantify the transport of air from the polar vortex to midlatitude. The intensity of the polar barrier is increasing with height from 400 to 550 K and is nearly constant above. During periods with a cold and undisturbed vortex, favorable to chlorine activation, the transport is very weak. This suggests that the midwinter vortex filamentation plays a minor role in the midlatitude ozone decline. In the opposite limit, during a stratospheric warming up to 30% of the polar vortex air is transported to midlatitudes. The cumulative transport from early January to end of April across the polar edge varies from almost 5% of the polar vortex air at 675 K in 1997 to 50% at 435 K in 1999.

Hauchecorne, Alain; Godin, Sophie; Marchand, Marion; Heese, Birgit; Souprayen, Claude

2002-10-01

109

Ozone profile measurements within, at the edge of, and outside the Antarctic polar vortex in the spring of 1988  

SciTech Connect

Ozone and temperature were measured during 38 balloon soundings at McMurdo Station, Antarctica (78{degree}S), in the spring of 1988. Because of the motion of the Antarctic polar vortex, measurements were obtained within, at the edge of, and outside the vortex. Although the polar vortex did not remain over McMurdo as it did in 1986 and 1987, it was overhead long enough to establish that ozone depletion was less extensive and ended earlier than in either 1986 or 1987. In the vortex the ozone mixing ratio at 18 km decayed with an exponential half-life of 29 days compared to 25 and 12 days in 1986 and 1987. While ozone partial pressure in the 16-18 km layer decayed to values as low as 10 nbar in 1986 and 3 nbar in 1987, ozone partial pressure dropped to only 60-70 nbar in 1988 in the depleted region, a reduction of 30 to 50%. Even with these differences in degree of ozone depletion there were similarities to previous measurements. Ozone depletion was caused by a sink between 12 and 20 km, and primary depletion was episodic, occurring in periods of <10 days. Measurements at the edge of the vortex displayed the ozone layering observed in 1986 and 1987 and suggest the exchange of ozone rich and poor air across the vortex wall in the 12-20 km layer. Outside the vortex, vertical profiles displayed a region of high ozone and constant temperature above 20 km.

Deshler, T.; Hofmann, D.J.; Hereford, J.V. (Univ. of Wyoming, Laramie (USA))

1990-06-20

110

CO as a marker and probe of polar vortex structure in the upper stratosphere and mesosphere  

NASA Astrophysics Data System (ADS)

We present new ground-based measurements of polar stratospheric and mesospheric CO showing that it serves as an excellent tracer of vortex position, size, and descent at an altitude range where other information may be sparse or unreliable. Observations were made with a mm-wave spectrometer at Thule, Greenland (76.5o N, 68.7o W), and involved almost-daily measurements between January 17 and March 4, 2002. Our analysis is supplemented with occasional observations made at the geographic South Pole during both summer and winter periods of 1999. Mixing ratio profiles are retrieved from pressure-broadened line shape measurements of the 230 GHz rotational emission line, using a spectrometer with a bandwidth of 50 MHz and a resolution of about 65 kHz. Although Doppler broadening increasingly dominates over pressure broadening in the mesosphere, eventually frustrating profile retrieval, extensive testing shows that rather accurate retrievals (< ±10% total error) can be obtained up to about 70 km, and typically within ± 20% at 80 km, with use of a Voigt line shape. Additional uncertainties may be introduced by lack of accurate knowledge of daily local temperature and pressure data for this altitude region, but we plan to use a co-located high-altitude Lidar probe for temperature retrievals in 2003. We find CO to be a very good marker for the upper vortex (e.g. 50-70 km), in agreement with recent analysis of 1991-92 ISAMS data by Allen et al. [J. Atmos. Sci. 56, 563-583, 1999]. Large changes in the vertical profile are evident from outside to inside the polar vortex in this altitude range. Observed short-term changes at 50-70 km are consistent with vortex position below 50 km. Relative to its January height just outside the vortex, we find that the CO mixing ratio peak had descended by ˜10 km (to ˜55 km altitude) within the vortex by late January of 2002, while the external peak altitude is already much lower (˜65 km) than the CO peak at low latitudes or in polar summer. From earlier South Pole trial observations (with poorer signal/noise ratio) we find the total column density above 40 km in polar summer to be only 6-7% of its winter value. We have also compared our total column density values above 64 km to the same computations by Solomon et al. [J. Atmos. Sci., 42, 1072-1083, 1985] from a 2-D photochemical transport model and find excellent agreement with values for high-latitude northern winters (˜1.5x1016 molecules/cm^2 calculated, versus an average of ˜1.8x1016 molecules/cm^2 observed, when outside the vortex in January -March 2002), as well as with the summer-winter difference noted above.

de Zafra, R. L.; Muscari, G.

2003-04-01

111

Dynamics of Venus' southern polar vortex from over two years of VIRTIS/Venus Express observations  

NASA Astrophysics Data System (ADS)

polar region of Venus, using measurements from the VIRTIS instrument from the Venus Express Mission, revealed it to be in constant dynamic change, with the southern polar vortex displaced from the rotational geometry of the planet [1]. Here, we place these results in the context of measurements taken over a two year period. We examine the dynamics of the southern polar region based on measurements of winds at the 45 and 65 km levels, detected from cloud motion monitoring by the VIRTIS instrument. The wind velocity components were determined by an automatic cloud-tracking technique based on evaluating the similarity between pairs of images of cloud structures at a specific atmospheric altitude, separated by a short time interval. The images were obtained at infrared wavelengths of 1.74 and 2.3 ?m, for the night side, and 3.9 and 5.0 ?m, for both the day and night sides. These wavelengths are sensitive to radiation originating from levels close to the base and to the top of the cloud deck, respectively. The technique assumes that the clouds are passive tracers of the atmospheric mass flow, and that the cloud structure does not change substantially between the two images. Our objectives have been 1) to provide horizontal maps of direct wind measurements at cloud tops and in the lower cloud level with a high spatial resolution; 2) to characterize the southern polar vortex as to its motion, rotation rate and dynamical stability; 3) to constrain the contribution of the circumpolar circulation to the angular momentum budget; and 4) to provide valuable information for Venus climate modelling, for the planning of future probe or balloon missions, and to examine the Venus polar vortex in the context of other planetary vortices. The circulation in the southern polar region is dominated by the zonal flow, which is much stronger than the meridional circulation. The latitudinal profiles show a relatively smooth variation and the vertical shear between the 45-km and 65-km levels is on the order of 5-10 ms-1. The horizontal structure of the zonal and meridional wind components indicate that wavenumber-2 thermal tides are likely to be present.

Luz, D.; Berry, D. L.; Peralta, J.; Piccioni, G.

2011-10-01

112

Vortex Rossby waves on smooth circular vortices Part II. Idealized numerical experiments for tropical cyclone and polar vortex interiors  

Microsoft Academic Search

Idealized linear and nonlinear numerical experiments are carried out to test the predictions of the theory developed in Brunet and Montgomery (Vortex Rossby Waves on Smooth Circular Vortices Part I: Theory (pages 153-177, this issue)). For a monopolar tropical cyclone-like vortex whose strength lies between a tropical depression and tropical storm, linear theory remains uniformly valid in time in the

Michael T. Montgomerya; Gilbert Brunet

113

The great Arctic cyclone of August 2012  

NASA Astrophysics Data System (ADS)

On 2 August 2012 a dramatic storm formed over Siberia, moved into the Arctic, and died in the Canadian Arctic Archipelago on 14 August. During its lifetime its central pressure dropped to 966 hPa, leading it to be dubbed ‘The Great Arctic Cyclone of August 2012’. This cyclone occurred during a period when the sea ice extent was on the way to reaching a new satellite-era low, and its intense behavior was related to baroclinicity and a tropopause polar vortex. The pressure of the storm was the lowest of all Arctic August storms over our record starting in 1979, and the system was also the most extreme when a combination of key cyclone properties was considered. Even though, climatologically, summer is a ‘quiet’ time in the Arctic, when compared with all Arctic storms across the period it came in as the 13th most extreme storm, warranting the attribution of ‘Great’.

Simmonds, Ian; Rudeva, Irina

2012-12-01

114

IHY-IPY conference report from Polar Gateways Arctic Circle Sunrise 2008  

NASA Astrophysics Data System (ADS)

Polar, heliophysical, and planetary science topics related to the International Heliophysical and Polar Years 2007-2009 were addressed during this unique circumpolar conference hosted January 23-29, 2008 at the new Barrow Arctic Research Center of the Barrow Arctic Science Consortium in Barrow, Alaska. Science presentations spanned the solar system from the polar Sun and heliospheric environment to Earth, Moon, Mars, Jupiter, Saturn, the Kuiper Belt, and the solar wind termination shock now crossed by both Voyager spacecraft. Many of the science presentations were made remotely via video conference or teleconference from Sweden, Norway, Russia, Canada, Antarctica, and the United States, spanning up to thirteen time zones (Alaska to Russia) at various times during the conference. U.S. remote contributions came from the University of Alaska at Fairbanks, the University of California at Berkeley, the University of Arizona, NASA Jet Propulsion Laboratory, and NASA Goddard Space Flight Center. Convening during the first week of 2008 Arctic sunrise at Barrow, this conference served as a prelude that year to international Sun-Earth Day celebrations for IHY, while also commemorating Barrow scientific and native cultural support for the first International Polar Year 1882-1883. Extensive educational outreach activities were conducted with the local Barrow and Alaska North Slope communities and through the NASA Digital Learning Network live from the "top of the world" at Barrow. The conference proceedings are Internet accessible via the home page at http://polargateways2008.org/.

Cooper, John; Kauristie, Kirsti; Weatherwax, Allan; Thompson, Barbara; Sheehan, Glenn; Smith, Roger; Sandahl, Ingrid

115

Quantification of the transport of chemical constituents from the polar vortex to midlatitudes in the lower stratosphere using the high-resolution advection model MIMOSA and effective diffusivity  

Microsoft Academic Search

The observed decrease of ozone in the northern midlatitude lower stratosphere is only partially reproduced by chemical models. The transport of ozone-depleted air from the polar vortex is one of the proposed mechanisms to explain the discrepancy. Here we present a study on the quantification of the air mass transported from the polar vortex to midlatitude during the four winters

Alain Hauchecorne; Sophie Godin; Marion Marchand; Birgit Heese; Claude Souprayen

2002-01-01

116

Generating radial or azimuthal polarization by axial sampling of circularly polarized vortex beams.  

PubMed

A laser beam with circular polarization can be converted into either radial or azimuthal polarization by a microfabricated spiral phase plate and a radial (or azimuthal)-type linear analyzer. The resulting polarization is axially symmetric and is able to produce tightly focused light fields beyond the diffraction limit. We describe in detail the theory behind the technique and the experimental verification of the polarization both in the far field and at the focus of a high numerical aperture lens. Vector properties of the beam under strong focusing conditions were observed by comparing the fluorescence images corresponding to the focal intensity distribution for both radial and azimuthal polarizations. The technique discussed here may easily be implemented to a wide range of optical instruments and devices that require the use of tightly focused light beams. PMID:17952194

Moh, K J; Yuan, X-C; Bu, J; Burge, R E; Gao, Bruce Z

2007-10-20

117

Increased UV radiation due to polar ozone chemical depletion and vortex occurrences at Southern Sub-polar Latitudes in the period [1997 2005  

NASA Astrophysics Data System (ADS)

The variability of total ozone and UV radiation from Total Ozone Mapping Spectrometer (TOMS) measurements is analyzed as a function of polar vortex occurrences over the southern subpolar regions during the 1997 2005 period. The analysis of vortex occurrences showed high interannual variability in the 40° S 60° S latitude band with a longitudinal asymmetry showing the largest frequencies over the 90° W 90° E region. The impact of vortex occurrences on UV radiation and ozone in clear sky conditions was determined from the comparison between the measurements inside the vortex and a climatology obtained from data outside the vortex over the studied period. Clear sky conditions were determined from TOMS reflectivity data. For measurements outside the vortex, clear sky conditions were selected for reflectivity values lower than 7.5%, while for measurements inside the vortex, a relaxed threshold was determined from statistically similar UV values as a function of reflectivity. UV changes and ozone differences from the climatology were analyzed in the 40° S 50° S and 50° S 60° S latitude bands during the spring period (September to November). The largest UV increases and ozone decreases, reaching ~200% and ~65%, respectively, were found in the 50° S 60° S latitude band in September and October. The heterogeneous ozone loss during vortex occurrences was estimated using a chemical transport model. The largest impact of vortex occurrences was found in October with mean UV increase, total ozone decrease and accumulated ozone loss in the 350 650 K range of, respectively, 47%, 30% and 57%. The region close to South America is the most affected by the Antarctic ozone depletion due to the combined effect of large number of vortex occurrences, lower cloud cover and large ozone decrease. This region would be the most vulnerable in case of cloud cover decrease, due to more frequent occurrence of ozone poor air masses during austral spring.

Pazmiño, A. F.; Godin-Beekmann, S.; Luccini, E. A.; Piacentini, R. D.; Quel, E. J.; Hauchecorne, A.

2008-09-01

118

Increased UV radiation due to polar ozone chemical depletion and vortex occurrences at southern sub-polar latitudes in the period (1997-2005)  

NASA Astrophysics Data System (ADS)

The variability of total ozone and UV radiation from Total Ozone Mapping Spectrometer (TOMS) measurements is analyzed as a function of polar vortex occurrences over the southern subpolar regions during the 1997-2005 period. The analysis of vortex occurrences showed high interannual variability in the 40° S-60° S latitude band with a longitudinal asymmetry showing the largest frequencies over the 90° W-90° E region. The impact of vortex occurrences on UV radiation and ozone in clear sky conditions was determined from the comparison between the measurements inside the vortex and a climatology obtained from data outside the vortex over the studied period. Clear sky conditions were determined from TOMS reflectivity data. For measurements outside the vortex, clear sky conditions were selected for reflectivity values lower than 7.5%, while for measurements inside the vortex, a relaxed threshold was determined from statistically similar UV values as a function of reflectivity. UV changes and ozone differences from the climatology were analyzed in the 40° S-50° S and 50° S-60° S latitude bands during the spring period (September to November). The largest UV increases and ozone decreases, reaching 200% and 65%, respectively, were found in the 50° S-60° S latitude band in September and October. The heterogeneous ozone loss during vortex occurrences was estimated using a chemical transport model. The largest impact of vortex occurrences was found in October with mean UV increase, total ozone decrease and accumulated ozone loss in the 350 K-650 K range of respectively 47%, 32% and 63%. The region close to South America is the most affected by the Antarctic ozone depletion due to the combined effect of large number of vortex occurrences, lower cloud cover and large ozone decrease. This region would be the most vulnerable in case of cloud cover decrease linked to climate change, due to more frequent occurrence of ozone poor air masses during austral spring.

Pazmino, A. F.; Godin-Beekmann, S.; Luccini, E. A.; Piacentini, R. D.; Quel, E. J.; Hauchecorne, A.

2008-04-01

119

Evidence for bromine monoxide in the free troposphere during the Arctic polar sunrise  

NASA Astrophysics Data System (ADS)

During the Arctic polar springtime, dramatic ozone losses occur not only in the stratosphere but also in the underlying troposphere. These tropospheric ozone loss events have been observed over large areas, in the planetary boundary layer (PBL) throughout the Arctic. They are associated with enhanced concentrations of halogen species and are probably caused by catalytic reactions involving bromine monoxide (BrO) and perhaps also chlorine monoxide (ClO). The origin of the BrO, the principle species driving the ozone destruction, is thought to be the autocatalytic release of bromine from sea salt accumulated on the Arctic snow pack, followed by photolytic and heterogeneous reactions which produce and recycle the oxide. Satellite observations have shown the horizontal and temporal extent of large BrO enhancements in the Arctic troposphere, but the vertical distribution of the BrO has remained uncertain. Here we report BrO observations obtained from a high-altitude aircraft that suggest the presence of significant amounts of BrO not only in the PBL but also in the free troposphere above it. We believe that the BrO is transported from the PBL into the free troposphere through convection over large Arctic ice leads (openings in the pack ice). The convective transport also lifts ice crystals and water droplets well above the PBL, thus providing surfaces for heterogeneous reactions that can recycle BrO from less-reactive forms and thereby maintain its ability to affect the chemistry of the free troposphere.

McElroy, C. T.; McLinden, C. A.; McConnell, J. C.

1999-01-01

120

Measurement of Halogenated Dicarboxylic Acids in the Arctic Aerosols at Polar Sunrise  

Microsoft Academic Search

Halogenated dicarboxylic acids, such as bromomalonic (Br-C3), chlorosuccinic (Cl-C4) and bromosuccinic (Br-C4) acids, have been measured, for the first time, in the arctic aerosols dur- ing the polar sunrise experiment ALERT2000 (February to May). They were detected in the light spring, but not in the dark winter. Concentration ranges of halogenated diacids in the spring were 0.11-0.68 ng m?3 for

M. NARUKAWA; K. KAWAMURA; H. HATSUSHIKA; K. YAMAZAKI; S.-M. LI; J. W. BOTTENHEIM; K. G. ANLAUF

2003-01-01

121

Measurement of Halogenated Dicarboxylic Acids in the Arctic Aerosols at Polar Sunrise  

Microsoft Academic Search

Halogenated dicarboxylic acids, such as bromomalonic (Br-C3), chlorosuccinic (Cl-C4) and bromosuccinic (Br-C4) acids, have been measured, for the first time, in the arctic aerosols during the polar sunrise experiment ALERT2000 (February to May). They were detected in the light spring, but not in the dark winter. Concentration ranges of halogenated diacids in the spring were 0.11–0.68 ng m-3 for Br-C3

M. Narukawa; K. Kawamura; H. Hatsushika; K. Yamazaki; S.-M. Li; J. W. Bottenheim; K. G. Anlauf

2003-01-01

122

The last polar dinosaurs: high diversity of latest Cretaceous arctic dinosaurs in Russia  

Microsoft Academic Search

A latest Cretaceous (68 to 65 million years ago) vertebrate microfossil assemblage discovered at Kakanaut in northeastern\\u000a Russia reveals that dinosaurs were still highly diversified in Arctic regions just before the Cretaceous–Tertiary mass extinction\\u000a event. Dinosaur eggshell fragments, belonging to hadrosaurids and non-avian theropods, indicate that at least several latest\\u000a Cretaceous dinosaur taxa could reproduce in polar region and were

Pascal Godefroit; Lina Golovneva; Sergei Shchepetov; Géraldine Garcia; Pavel Alekseev

2009-01-01

123

Observing the Arctic From Space: Educational Opportunities for an International Polar Year  

NASA Astrophysics Data System (ADS)

Recommendations for an International Polar Year (IPY) will require integrated circumpolar research projects using present and advanced technologies. The IPY will offer exceptional opportunities for participation by indigenous residents of the Arctic. Educational outreach will be an essential component of IPY programs, to improve science competence and citizen awareness through participation in IPY projects and utilization of educational products. An important and practical objective of IPY educational outreach is to recognize that the earth is a system and that it is best from space that we can acquire seasonal and secular atmospheric, terrestrial and oceanic environmental data. Acquisition of reliable ground truth data in support of remote sensing of geophysical and geochemical variables will be essential, especially with broad long-term coverage in the polar regions. It should be an essential element of the IPY program. In the United States NASA has developed a strategy for long-term monitoring of some key parameters needed to bring us closer to the answers we need regarding climate change in the Arctic and polar regions. Technology consists of a group of five polar satellites that make a suite of earth observations referred to as the "A-Train". Data from this group of satellites, as well as from the Orbital Carbon Observatory (OCO) and older Quikscat and new Seawinds radar missions, will provide focus for an education program based not only on the acquisition of polar data but also on how these data correlate with global observations. We recommend that an educational outreach secretariat be developed for each national program that will involve the indigenous people of the Arctic and elsewhere in acquisition of data relevant to satellite observations. The secretariat will provide for information transfer, coordination with scientific projects, opportunities for participation in project activities, communication of scientific results to the public, and greater participation of residents of circumpolar nations in polar science.

Kelley, J. J.; Yanow, G.; Alexander, V.; Johnson, L.

2003-12-01

124

3. Observing the Arctic from space: educational opportunities for an International Polar Year  

NASA Astrophysics Data System (ADS)

Recommendations for an International Polar Year (IPY) will require integrated circumpolar research projects using present and advanced technologies. The IPY will offer exceptional opportunities for participation by indigenous residents of the Arctic. Educational outreach will be an essential component of IPY programs, to improve science competence and citizen awareness through participation in IPY projects and utilization of educational products. An important and practical objective of IPY educational outreach is to recognize that the earth is a system and that it is best from space that we can acquire seasonal and secular atmospheric, terrestrial and oceanic environmental data. Acquisition of reliable ground truth data in support of remote sensing of geophysical and geochemical variables will be essential, especially with broad long-term coverage in the polar regions. It should be an essential element of the IPY program. In the United States NASA has developed a strategy for long-term monitoring of some key parameters needed to bring us closer to the answers we need regarding climate change in the Arctic and polar regions. Technology consists of a group of five polar satellites that make a suite of earth observations referred to as the "A-Train". Data from this group of satellites, as well as from the Orbital Carbon Observatory (OCO) and older Quikscat and new Seawinds radar missions, will provide focus for an education program based not only on the acquisition of polar data but also on how these data correlate with global observations. We recommend that an educational outreach secretariat be developed for each national program that will involve the indigenous people of the Arctic and elsewhere in acquisition of data relevant to satellite observations. The secretariat will provide for information transfer, coordination with scientific projects, opportunities for participation in project activities, communication of scientific results to the public, and greater participation of residents of circumpolar nations in polar science.

Kelley, J.; Yanow, G.; Alexander, V.; Johnson, L.

2003-04-01

125

The Arctic Human Health Initiative: a legacy of the International Polar Year 2007-2009  

PubMed Central

Background The International Polar Year (IPY) 2007–2008 represented a unique opportunity to further stimulate cooperation and coordination on Arctic health research and increase the awareness and visibility of Arctic regions. The Arctic Human Health Initiative (AHHI) was a US-led Arctic Council IPY coordinating project that aimed to build and expand on existing International Union for Circumpolar Health (IUCH) and Arctic Council human health interests. The project aimed to link researchers with potential international collaborators and to serve as a focal point for human health research, education, outreach and communication activities during the IPY. The progress of projects conducted as part of this initiative up until the end of the Arctic Council Swedish chairmanship in May 2013 is summarized in this report. Design The overall goals of the AHHI was to increase awareness and visibility of human health concerns of Arctic peoples, foster human health research, and promote health strategies that will improve health and well-being of all Arctic residents. Proposed activities to be recognized through the initiative included: expanding research networks that will enhance surveillance and monitoring of health issues of concern to Arctic peoples, and increase collaboration and coordination of human health research; fostering research that will examine the health impact of anthropogenic pollution, rapid modernization and economic development, climate variability, infectious and chronic diseases, intentional and unintentional injuries, promoting education, outreach and communication that will focus public and political attention on Arctic health issues, using a variety of publications, printed and electronic reports from scientific conferences, symposia and workshops targeting researchers, students, communities and policy makers; promoting the translation of research into health policy and community action including implementation of prevention strategies and health promotion; and promoting synergy and strategic direction of Arctic human health research and health promotion. Results As of 31 March, 2009, the official end of the IPY, AHHI represented a total of 38 proposals, including 21 individual Expressions of Intent (EoI), and 9 full proposals (FP), submitted to the IPY Joint Committee for review and approval from lead investigators from the US, Canada, Greenland, Norway, Finland, Sweden and the Russian Federation. In addition, there were 10 National Initiatives (NI-projects undertaken during IPY beyond the IPY Joint Committee review process). Individual project details can be viewed at www.arctichealth.org. The AHHI currently monitors the progress of 28 individual active human health projects in the following thematic areas: health network expansion (5 projects), infectious disease research (7 projects), environmental health research (7 projects), behavioral and mental health research (4 projects), and outreach education and communication (5 projects). Conclusions While some projects have been completed, others will continue well beyond the IPY. The IPY 2007–2008 represented a unique opportunity to further stimulate cooperation and coordination on Arctic health research and increase the awareness and visibility of Arctic regions.

Parkinson, Alan J.

2013-01-01

126

Probing the Spin Polarization of Current by Soft X-Ray Imaging of Current-Induced Magnetic Vortex Dynamics  

NASA Astrophysics Data System (ADS)

Time-resolved soft x-ray transmission microscopy is applied to image the current-induced resonant dynamics of the magnetic vortex core realized in a micron sized Permalloy disk. The high spatial resolution better than 25 nm enables us to observe the resonant motion of the vortex core. The result also provides the spin polarization of the current to be 0.67±0.16 for Permalloy by fitting the experimental results with an analytical model in the framework of the spin-transfer torque.

Kasai, Shinya; Fischer, Peter; Im, Mi-Young; Yamada, Keisuke; Nakatani, Yoshinobu; Kobayashi, Kensuke; Kohno, Hiroshi; Ono, Teruo

2008-12-01

127

Do tropospheric clouds influence Polar Stratospheric cloud occurrence in the Arctic?  

NASA Astrophysics Data System (ADS)

The type of Polar stratospheric clouds (PSCs) as well as their temporal and spatial extent are important for the occurrence of heterogeneous reactions in the polar stratosphere. The formation of PSCs depends strongly on temperature. However, the mechanisms of the formation of solid PSCs are still poorly understood. Recent satellite studies of Antarctic PSCs have shown that their formation can be associated with deep-tropospheric clouds which have the ability to cool the lower stratosphere radiatively and/or adiabatically. In the present study, lidar measurements aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite were used to investigate whether the formation of Arctic PSCs can be associated with deep-tropospheric clouds as well. Deep-tropospheric cloud systems have a vertical extent of more than 6.5 km with a cloud top height above 7 km altitude. PSCs observed by CALIPSO during the Arctic winter 2007/2008 were classified according to their type (STS, NAT, or ice) and to the kind of underlying tropospheric clouds. Our analysis reveals that 172 out of 211 observed PSCs occurred in connection with tropospheric clouds. 72% of these 172 observed PSCs occured above deep-tropospheric clouds. We also find that the type of PSC seems to be connected to the characteristics of the underlying tropospheric cloud system. During the Arctic winter 2007/2008 PSCs consisting of ice were mainly observed in connection with deep-tropospheric cloud systems while no ice PSC was detected above cirrus. Furthermore, we find no correlation between the occurrence of PSCs and the top temperature of tropospheric clouds. These findings suggest that Arctic PSC formation is connected to adiabatice cooling, i.e. dynamic effects rather than radiative cooling.

Achtert, P.; Karlsson Andersson, M.; Khosrawi, F.; Gumbel, J.

2011-12-01

128

Increased UV radiation due to polar ozone chemical depletion and vortex occurrences at Southern Subpolar Latitudes in the period [1997 2005  

Microsoft Academic Search

The variability of total ozone and UV radiation from Total Ozone Mapping Spectrometer (TOMS) measurements is analyzed as a function of polar vortex occurrences over the southern subpolar regions during the 1997 2005 period. The analysis of vortex occurrences showed high interannual variability in the 40° S 60° S latitude band with a longitudinal asymmetry showing the largest frequencies over

A. F. Pazmiño; S. Godin-Beekmann; E. A. Luccini; R. D. Piacentini; E. J. Quel; A. Hauchecorne

2008-01-01

129

The role of stationary and transient planetary waves in the maintenance of stratospheric polar vortex regimes in Northern Hemisphere winter  

NASA Astrophysics Data System (ADS)

Using 1958-2002 NCEP/NCAR reanalysis data, we investigate stationary and transient planetary wave propagation and its role in wave-mean flow interaction which influences the state of the polar vortex (PV) in the stratosphere in Northern Hemisphere (NH) winter. This is done by analyzing the Eliassen-Palm (E-P) flux and its divergence. We find that the stationary and transient waves propagate upward and equatorward in NH winter, with stronger upward propagation of stationary waves from the troposphere to the stratosphere, and stronger equatorward propagation of transient waves from mid-latitudes to the subtropics in the troposphere. Stationary waves exhibit more upward propagation in the polar stratosphere during the weak polar vortex regime (WVR) than during the strong polar vortex regime (SVR). On the other hand, transient waves have more upward propagation during SVR than during WVR in the subpolar stratosphere, with a domain of low frequency waves. With different paths of upward propagation, both stationary and transient waves contribute to the maintenance of the observed stratospheric PV regimes in NH winter.

Li, Qian; Graf, Hans-F.; Cui, Xuefeng

2011-01-01

130

Arctic and Antarctic exploration including the contributions of physicians and effects of disease in the polar regions.  

PubMed

A history of Arctic and Antarctic exploration, whether to find a Northwest Passage, North Pole, or South Pole, is a story of triumph and tribulation. The hardship experienced by polar explorers in the last 1000 years permeates the tales of achievement. Physicians and surgeons have played prominent roles in all major polar explorations. No significant Arctic voyage, particularly in the last 300 years, was made without a member of the party trained in the management of medical emergencies and in basic surgery. During times of health, surgeons functioned as the voyage naturalists with expertise in biology, botany, zoology, and the writing of scientific catalogs. Spurred by our interest and fascination with the history of polar exploration, we reviewed the roles of physicians and natural scientists in Arctic and Antarctic adventures. PMID:10232525

Fodstad, H; Kondziolka, D; Brophy, B P; Roberts, D W; Girvin, J P

1999-05-01

131

Post-Equinox Evolution of Titan’s Detached Haze and South Polar Vortex Cloud  

NASA Astrophysics Data System (ADS)

Instruments on the Cassini spacecraft discovered new phenomena related to the (presumably) seasonal behavior of photochemical haze and formation of the winter polar vortex. West et al. 2011 (Geophys. Res. Lett. , 380 , L06204. doi: 10.1029/2011GL046843) described a ‘detached’ haze layer that dropped in altitude from about 500 km in 2005 to about 360 km by late 2010. New images from the Cassini ISS camera show that the appearance of a detached layer is produced by a gap in the haze vertical profile and it is the gap rather than a haze layer that drops in altitude. Intensity profiles from different epochs form an envelope when plotted on top of each other, and the downward movement of the gap can be most easily seen when plotted that way. The movement of a gap rather than movement of a layer of enhanced haze density was suspected in the earlier publication but now it is more apparent. In recent months the gap became very shallow and the limb intensity profiles at a pixel scale ~10 km/pixel evolved from one local maximum/minimum into two local minima/maxima of smaller amplitude and appear to be trending toward the disappearance of relative maxima and minima, leaving a smooth envelope. These observations will require new developments in coupled dynamical and haze microphysical models as none of the current models account for this behavior. Titan’s south polar vortex cloud was detected concurrently by the ISS, VIMS, and CIRS instruments on Cassini in May of 2012. It has an unusual color (more yellow than Titan’s main haze in ISS images), morphology and texture (suggestive of a condensate cloud experiencing open cell convection) and displays a spectral feature at 220 cm-1 (Jennings et al., 2012, Astrophys. J. Lett. 761, L15 DOI: 10.1088/2041-8205/761/1/L15). These attributes point to a condensate of unknown composition. The haze patch is seen in images up to the present (July, 2013), but the latest images suggest a ‘softening’ or more diffuse edge than the earlier images. The feature is being engulfed by shadow as the season progresses, eventually preventing future observations in reflected sunlight. Acknowledgement: Part of this work was performed by the Jet Propulsion Lab, Calif. Inst. Of Technology.

West, Robert A.; Ovanessian, A.; Del Genio, A.; Turtle, E. P.; Perry, J.; NcEwen, A.; Ray, T.; Roy, M.

2013-10-01

132

The last polar dinosaurs: high diversity of latest Cretaceous arctic dinosaurs in Russia  

NASA Astrophysics Data System (ADS)

A latest Cretaceous (68 to 65 million years ago) vertebrate microfossil assemblage discovered at Kakanaut in northeastern Russia reveals that dinosaurs were still highly diversified in Arctic regions just before the Cretaceous-Tertiary mass extinction event. Dinosaur eggshell fragments, belonging to hadrosaurids and non-avian theropods, indicate that at least several latest Cretaceous dinosaur taxa could reproduce in polar region and were probably year-round residents of high latitudes. Palaeobotanical data suggest that these polar dinosaurs lived in a temperate climate (mean annual temperature about 10°C), but the climate was apparently too cold for amphibians and ectothermic reptiles. The high diversity of Late Maastrichtian dinosaurs in high latitudes, where ectotherms are absent, strongly questions hypotheses according to which dinosaur extinction was a result of temperature decline, caused or not by the Chicxulub impact.

Godefroit, Pascal; Golovneva, Lina; Shchepetov, Sergei; Garcia, Géraldine; Alekseev, Pavel

2009-04-01

133

Mercury speciation in brain tissue of polar bears (Ursus maritimus) from the Canadian Arctic.  

PubMed

Methylmercury (MeHg) is a neurotoxicant that has been found at elevated concentrations in the Arctic ecosystem. Little is known about its internal dose in wildlife such as polar bears. We measured concentrations of mercury (Hg) in three different brain regions (cerebellum, frontal lobe and brain stem) of 24 polar bears collected from the Nunavik, Canada between 2000 and 2003. Speciation of Hg was measured by High Performance Liquid Chromatography coupled to Inductively Coupled Plasma Mass Spectroscopy (HPLC-ICP-MS). Concentrations of mean total Hg in brain tissue were up to 625 times lower (0.28 ± 0.07 mg kg(-1) dry weight (dw) in frontal lobe, 0.23 ± 0.07 mg kg(-1) dw in cerebellum and 0.12 ± 0.0 3mg kg(-1) dw in brain stem) than the mean total Hg concentration previously reported in polar bear liver collected from Eastern Baffin Island. Methylmercury (MeHg) accounted for 100% of the Hg found in all three brain regions analyzed. These results suggest that polar bear might reduce the toxic effects of Hg by limiting the uptake into the brain and/or decrease the rate of demethylation so that Hg can be excreted from the brain more easily. The toxicokinetics and the blood-brain-barrier mechanisms of polar bears are still unknown and further research is required. PMID:22406289

Krey, Anke; Kwan, Michael; Chan, Hing Man

2012-03-08

134

Organochlorine contaminants in arctic marine food chains: identification, geographical distribution, and temporal trends in polar bears  

SciTech Connect

Contamination of Canadian arctic and subarctic marine ecosystems by organochlorine (OC) compounds was measured by analysis of polar bear (Ursus maritimus) tissues collected from 12 zones between 1982 and 1984. PCB congeners (S-PCB), chlordanes, DDT and metabolites, chlorobenzenes (S-CBz), hexachlorocyclohexane isomers (S-HC-H), and dieldrin were identified by high-resolution gas chromatography-mass spectrometry. Nonachlor-III, a nonachlor isomer in technical chlordane, was positively identified for the first time as an environmental contaminant. S-PCB and S-CHLOR accounted for >80% of the total organochlorines in adipose tissue. Six PCB congeners constituted approximately 93% of S-PCB in polar bears. Levels of most OCs were lowest in the high Arctic, intermediate in Baffin Bay, and highest in Hudson Bay. Levels of ..cap alpha..-HCH were evaluated in zones influenced by surface runoff. Levels of S-CHLOR were four times higher and levels of the other OCs were two times higher in adipose tissue of bears from Hudson Bay and Baffin Bay in 1984 than in adipose tissue archived since 1969 from these areas; levels of S-DDT did not change.

Norstrom, R.J.; Simon, M.; Muir, D.C.G.; Schweinsburg, R.E.

1988-09-01

135

Infrared measurements throughout polar night using two AERIs in the Arctic  

NASA Astrophysics Data System (ADS)

The Extended-range Atmospheric Emitted Radiance Interferometer (E-AERI) is a moderate resolution (1 cm-1) Fourier transform infrared spectrometer for measuring the absolute downwelling infrared spectral radiance from the atmosphere between 400 and 3000 cm-1. The extended spectral range of the instrument permits monitoring of the 400-550 cm-1 (20-25 ?m) region, where much of the infrared surface cooling currently occurs in the dry air of the Arctic. The E-AERI provides information about radiative balance, trace gases, and cloud properties in the Canadian high Arctic. The instrument was installed at the Polar Environment Atmospheric Research Laboratory (PEARL) Ridge Lab at Eureka, Nunavut, in October 2008. Measurements are taken every seven minutes year-round (precipitation permitting), including polar night when the solar-viewing spectrometers are not operated. A similar instrument, the University of Idaho's Polar AERI (P-AERI), was installed at the Zero-altitude PEARL Auxiliary Laboratory (0PAL), 15 km away from the Ridge Lab, from March 2006 to June 2009. During the period of overlap, these two instruments provided calibrated radiance measurements from two different altitudes. Retrievals of total columns of various trace gases are being evaluated using a prototype version of the retrieval algorithm SFIT2 modified to analyze emission features. In contrast to solar absorption measurements of atmospheric trace gases, which depend on sunlit clear-sky conditions, the use of emission spectra allows measurements year-round (except during precipitation events or when clouds are present). This capability allows the E-AERI to provide temporal coverage throughout the four months of polar night and to measure the radiative budget throughout the entire year. This presentation will describe the new E-AERI instrument, its performance evaluations, and clear sky vs. cloudy measurements.

Mariani, Z.; Strong, K.; Wolff, M.; Rowe, P.; Walden, V.; Fogal, P. F.; Duck, T.; Lesins, G.; Turner, D. S.; Cox, C.; Eloranta, E.; Drummond, J. R.; Roy, C.; Lachance, R. L.; Turner, D. D.; Hudak, D.; Lindenmaier, I. A.

2012-11-01

136

The Arctic winter 2010/11 as observed by GOME-2 and SCIAMACHY  

NASA Astrophysics Data System (ADS)

This talk should go into Session A47: The Severe Arctic Ozone Depletion of 2010-2011 (Drop menu for A47 was missing) Both GOME-2 and SCIAMACHY observed several trace gases (ozone, NO2, and OClO) during the Arctic winter 2010/11. Total ozone means north of 50 degress latitude were at a record low during March and April 2011. The stratospheric meteorology (atmospheric dynamics) and the evolution of total ozone during that winter very much resembled the Arctic winter 1996/1997 where the polar vortex was very stable and remained close to the north pole in March and April. In both Arctic winters 1996/1997 and 2010/11 an ozone hole coinciding with the polar vortex were clearly observed. Both Arctic winters were followed or preceded by Arctic winters with very high ozone (Arctic winters 1997/98 and 2009/2010). Chlorine activation as evident from SCIAMACHY OClO slant column observations were unusually high in March 2011 indicating severe ozone depletion. In addition, NO2 column amounts were very low suggesting substantial denitrification in early spring. Comparisons with the 3D Bremen CTM suggests polar ozone losses in the total column of about 120 DU (~35%) by the end of March. Ozone loss calculation based upon ozone profile limb measurements from SCIAMACHY using the vortex averaging method are under preparation and results will be presented.

Weber, M.; Hommel, R.; Aschmann, J.; Sinnhuber, B.; Kiesewetter, G.; Richter, A.; von Savigny, C.; Eichmann, K.

2011-12-01

137

Polar vision or tunnel vision the making of Canadian Arctic waters policy : The making of Canadian Arctic waters policy  

Microsoft Academic Search

This article examined the manner by which Canadian maritime Arctic policy is formulated. It suggests that this policy is largely the result of an ad hoc and reactive process. In general, the policy tends to be the product of a specific event initiated by a non-Canadian actor in the Canadian Arctic. In the early 1970s, this event was the voyages

Rob Huebert

1995-01-01

138

Dynamics of Venus' Southern hemisphere and South Polar Vortex from VIRTIS data obtained during the Venus Expres Mission  

NASA Astrophysics Data System (ADS)

The VIRTIS instrument onboard Venus Express observes Venus in two channels (visible and infrared) obtaining spectra and multi-wavelength images of the planet. The images have been used to trace the motions of the atmosphere at different layers of clouds [1-3]. We review the VIRTIS cloud image data and wind results obtained by different groups [1-3] and we present new results concerning the morphology and evolution of the South Polar Vortex at the upper and lower cloud levels with data covering the first 900 days of the mission. We present wind measurements of the South hemisphere obtained by cloud tracking individual cloud features and higher-resolution wind results of the polar region covering the evolution of the South polar vortex. The later were obtained by an image correlation algorithm run under human supervision to validate the data. We present day-side data of the upper clouds obtained at 380 and 980 nm sensitive to altitudes of 66-70 km, night-side data in the near infrared at 1.74 microns of the lower cloud (45-50 km) and day and night-side data obtained in the thermal infrared (wavelengths of 3.8 and 5.1 microns) which covers the dynamical evolution of Venus South Polar vortex at the cloud tops (66-70 km). We explore the different dynamics associated to the varying morphology of the vortex, its dynamical structure at different altitudes, the variability of the global wind data of the southern hemisphere and the interrelation of the polar vortex dynamics with the wind dynamics at subpolar and mid-latitudes. Acknowledgements: Work funded by Spanish MICIIN AYA2009-10701 with FEDER support and Grupos Gobierno Vasco IT-464-07. References [1] A. Sánchez-Lavega et al., Geophys. Res. Lett. 35, L13204, (2008). [2] D. Luz et al., Science, 332, 577-580 (2011). [3] R. Hueso, et al., Icarus doi:10.1016/j.icarus.2011.04.020 (2011)

Hueso, R.; Garate-Lopez, I.; Sanchez-Lavega, A.

2011-12-01

139

A closer look at Arctic ozone loss and polar stratospheric clouds  

NASA Astrophysics Data System (ADS)

The empirical relationship found between column-integrated Arctic ozone loss and the volume of polar stratospheric clouds inferred from meteorological analyses is updated and examined in more detail. The relationship is found to hold at different altitudes as well as in the column. Analysis of the photochemistry leading to the ozone loss shows that the early winter activation is limited by the photolysis of nitric acid. This step produces nitrogen dioxide which is converted to chlorine nitrate which in turn reacts with hydrogen chloride on any polar stratospheric clouds to form active chlorine. The rate-limiting step is the photolysis of nitric acid: this occurs at the same rate every year and so the interannual variation in the ozone loss is caused by the extent and persistence of the polar stratospheric clouds. In early spring the ozone loss rate increases as the solar insolation increases the photolysis of the chlorine monoxide dimer. However the length of the ozone loss period is determined by the photolysis of nitric acid which also occurs in the near ultraviolet. As a result of these compensating effects, the amount of the ozone loss is principally limited by the extent of original activation rather than its timing. In addition a number of factors, including the vertical changes in pressure and total inorganic chlorine as well as denitrification and renitrification, offset each other. As a result the extent of original activation is the most important factor influencing ozone loss. These results indicate that relatively simple parameterisations of Arctic ozone loss could be developed for use in coupled chemistry climate models.

Harris, N. R. P.; Lehmann, R.; Rex, M.; von der Gathen, P.

2010-03-01

140

A closer look at Arctic ozone loss and polar stratospheric clouds  

NASA Astrophysics Data System (ADS)

The empirical relationship found between column-integrated Arctic ozone loss and the potential volume of polar stratospheric clouds inferred from meteorological analyses is recalculated in a self-consistent manner using the ERA Interim reanalyses. The relationship is found to hold at different altitudes as well as in the column. The use of a PSC formation threshold based on temperature dependent cold aerosol formation makes little difference to the original, empirical relationship. Analysis of the photochemistry leading to the ozone loss shows that activation is limited by the photolysis of nitric acid. This step produces nitrogen dioxide which is converted to chlorine nitrate which in turn reacts with hydrogen chloride on any polar stratospheric clouds to form active chlorine. The rate-limiting step is the photolysis of nitric acid: this occurs at the same rate every year and so the interannual variation in the ozone loss is caused by the extent and persistence of the polar stratospheric clouds. In early spring the ozone loss rate increases as the solar insolation increases the photolysis of the chlorine monoxide dimer in the near ultraviolet. However the length of the ozone loss period is determined by the photolysis of nitric acid which also occurs in the near ultraviolet. As a result of these compensating effects, the amount of the ozone loss is principally limited by the extent of original activation rather than its timing. In addition a number of factors, including the vertical changes in pressure and total inorganic chlorine as well as denitrification and renitrification, offset each other. As a result the extent of original activation is the most important factor influencing ozone loss. These results indicate that relatively simple parameterisations of Arctic ozone loss could be developed for use in coupled chemistry climate models.

Harris, N. R. P.; Lehmann, R.; Rex, M.; von der Gathen, P.

2010-09-01

141

Changes in the polar vortex: Effects on Antarctic total ozone observations at various stations  

NASA Astrophysics Data System (ADS)

October mean total column ozone data from four Antarctic stations form the basis for understanding the evolution of the ozone hole since 1960. While these stations show similar emergence of the ozone hole from 1960 to 1980, the records are divergent in the last two decades. The effects of long-term changes in vortex shape and location are considered by gridding the measurements by equivalent latitude. A clear eastward shift of the mean position of the vortex in October with time is revealed, which changes the fraction of ozone measurements taken inside/outside the vortex for stations in the vortex collar region. After including only those measurements made inside the vortex, ozone behavior in the last two decades at the four stations is very similar. This suggests that dynamical influence must be considered when interpreting and intercomparing ozone measurements from Antarctic stations for detecting ozone recovery and ozone-related changes in Antarctic climate.

Hassler, B.; Bodeker, G. E.; Solomon, S.; Young, P. J.

2011-01-01

142

Particle size distributions in Arctic polar stratospheric clouds, growth and freezing of sulfuric acid droplets, and implications for cloud formation  

Microsoft Academic Search

The paper uses particle size and volume measurements obtained with the forward scattering spectrometer probe model 300 during January and February 1989 in the Airborne Arctic Stratospheric Experiment to investigate processes important in the formation and growth of polar stratospheric cloud (PSC) particles. It is suggested on the basis of comparisons of the observations with expected sulfuric acid droplet deliquescence

James E. Dye; D. Baumgardner; B. W. Gandrud; S. R. Kawa; K. K. Kelly; M. Loewenstein; G. V. Ferry; K. R. Chan; B. L. Gary

1992-01-01

143

Sailing the Open Polar Sea...Again: What Are You Teaching Your Children about the Arctic Ocean?  

ERIC Educational Resources Information Center

|Relates how a blunder about the Arctic Ocean and the polar ice cap made by the author in his first year of teaching led to a successful learning experience. Lists five important discussion topics that social studies teachers should use to teach about this remote, but strategic, part of the world. (LS)|

Stockard, James W. Jr.

1989-01-01

144

A Proposed Arctic Ocean Field Program During the International Polar Year 2007-2008  

Microsoft Academic Search

The Arctic Ocean represents a glaring void of measurements appropriate for monitoring and understanding the climate changes currently occurring in the Arctic region. We propose a field program in the central Arctic Ocean to develop and improve methods for the long-term monitoring of the Arctic atmosphere, ice, and ocean and the interactions among them, and to study physical processes crucial

O. P. Persson

2004-01-01

145

Generation of ultra-short-pulse laser beams with axially symmetric polarization or optical vortex and their interactions with plasma  

NASA Astrophysics Data System (ADS)

In the laser-plasma interaction, the laser beam is treated as a linearly polarized plane wave. However there are many categories of electromagnetic wave (EMW) which depend on the spatial variations of polarization and phase. Our interest is how the interaction of charged particles with EMW and the resultant macroscopic behaviors of the plasma change when introducing spatially controlled polarization and phase. Now we aim at the generation of the ultra-short-pulse laser beam having the circular polarization, the axially symmetric polarization (radially or azimuthally symmetric polarization) and the optical vortex (linearly or circularly polarized Laguerre beam). Optics generating such beams are fabricated and installed into Ti:sapphire laser (T^6 laser, 100mJ/100fs at 800-nm wavelength). Detailed properties of polarization/phase converted beam and preliminary experimental results concerning electron acceleration will be presented. We would like to thank Dr. V. G. Niziev of Institute of Laser and Information Technologies, Russia for his discussion that motivates this study.

Miyanaga, N.; Sueda, K.; Miyaji, G.; Ohbayashi, K.; Sakabe, S.; Okihara, S.; Nakatsuka, M.; Esirkepov, T.; Nishihara, K.

2001-10-01

146

Warm to cold polar climate transitions over the last 15,000 years: A paleoclimatology record from the raised beaches of northern Norway  

Microsoft Academic Search

Because of the strength of the cold, dry arctic high pressure vortex, and the absence of multiple air-mass sources, climate records from the polar region tend to display a cleaner signal than those from mid-latitude settings. The high arctic presents unique opportunities for the prediction of the natural background pattern of climate change prior to the disturbances generated by manmade

C. H. Fletcher; R. H. Fairbridge; J. K. Moeller; A. J. Long

1991-01-01

147

ECMWF Analyses and Forecasts of Stratospheric Winter Polar Vortex Breakup: September 2002 in the Southern Hemisphere and Related Events.  

NASA Astrophysics Data System (ADS)

Breakup of the polar stratospheric vortex in the Northern Hemisphere is an event that is known to be predictable for up to a week or so ahead. This is illustrated using data from the 45-yr ECMWF Re-Analysis (ERA-40) for the sudden warmings of January 1958 and February 1979 and operational ECMWF data for February 2003. It is then shown that a similar level of skill was achieved in operational forecasts for the split of the southern stratospheric vortex in late September 2002. The highly unusual flow conditions nevertheless exposed a computational instability of the forecast model. Analyses and forecasts from reruns using improved versions of the forecasting system are presented. Isentropic maps of potential vorticity and specific humidity provide striking pictures of the advective processes at work. Forecasts as well as analyses are shown to be in good agreement with radiosonde measurements of the temperature changes associated with vortex movement, distortion, and breakup during August and September. Forecasts from 17 September onward capture the remarkable temperature rise of about 60°C recorded at 20 hPa by the Halley radiosonde station as the vortex split. Objective forecast verification and data denial experiments are used to characterize the performance of the observing and data assimilation systems and to infer overall forecast, analysis, and observation accuracy. The observations and analyses from 1957 onward in the ERA-40 archive confirm the extreme nature of the 2002 event. Secondary vortex development by barotropic instability is also discussed; in analyses for early October 2002, the process is active in the breakup of the weaker of the two vortices formed by the late-September split.

Simmons, Adrian; Hortal, Mariano; Kelly, Graeme; McNally, Anthony; Untch, Agathe; Uppala, Sakari

2005-03-01

148

The future of soil invertebrate communities in polar regions: different climate change responses in the Arctic and Antarctic?  

PubMed

The polar regions are experiencing rapid climate change with implications for terrestrial ecosystems. Here, despite limited knowledge, we make some early predictions on soil invertebrate community responses to predicted twenty-first century climate change. Geographic and environmental differences suggest that climate change responses will differ between the Arctic and Antarctic. We predict significant, but different, belowground community changes in both regions. This change will be driven mainly by vegetation type changes in the Arctic, while communities in Antarctica will respond to climate amelioration directly and indirectly through changes in microbial community composition and activity, and the development of, and/or changes in, plant communities. Climate amelioration is likely to allow a greater influx of non-native species into both the Arctic and Antarctic promoting landscape scale biodiversity change. Non-native competitive species could, however, have negative effects on local biodiversity particularly in the Arctic where the communities are already species rich. Species ranges will shift in both areas as the climate changes potentially posing a problem for endemic species in the Arctic where options for northward migration are limited. Greater soil biotic activity may move the Arctic towards a trajectory of being a substantial carbon source, while Antarctica could become a carbon sink. PMID:23278945

Nielsen, Uffe N; Wall, Diana H

2013-01-01

149

Past and recent tritium levels in Arctic and Antarctic polar caps  

NASA Astrophysics Data System (ADS)

Tritium concentration was measured in snow deposited at the GRIP site (central Greenland) and at the Vostok station (east Antarctica) from snow pits covering the period 1980-1990. The objective of the study was to investigate tritium concentrations in polar regions several decades after the bomb peak of the sixties and to put them in the context of available data for environmental tritium in the Arctic and the Antarctic over the last five decades. The tritium content of the samples was measured by mass spectrometry using the helium-3 regrowth method. In Antarctica, the tritium concentrations are in the range 70-110 TU. The comparison of the bomb tritium history at different locations show that tritium levels increase moving inland, where vapour pressure becomes extremely low and therefore more sensitive to the intrusion of stratospheric air masses highly enriched in tritium. Although most tritium fallout occurred in the Northern hemisphere, the tritium levels in central Greenland in the 80's, in the range 10-40 TU, are significantly lower than at Vostok. Unlike Antarctica, no such continental effect is observed in Greenland, due to the higher water vapour content of the air masses, as evidenced by the much higher snow accumulation rate. Whereas tritium fallout in Antarctica appears to occur as a result of direct injections of stratospheric tritium during winter, Arctic fallout are the result of the dominant spring injection of stratospheric air at mid-latitude, in line with the deposition of other stratospheric tracers.

Fourré, Elise; Jean-Baptiste, Philippe; Dapoigny, Arnaud; Baumier, Dominique; Petit, Jean-Robert; Jouzel, Jean

2006-05-01

150

Observational evidence for chemical ozone depletion over the Arctic in winter 1991-92  

Microsoft Academic Search

LONG-TERM depletion of ozone has been observed since the early 1980s in the Antarctic polar vortex, and more recently at mid-latitudes in both hemispheres, with most of the ozone loss occurring in the lower stratosphere1. Insufficient measurements of ozone exist, however, to determine decadal trends in ozone concentration in the Arctic winter. Several studies of ozone concentrations in the Arctic

Peter von der Gathen; Markus Rex; Neil R. P. Harris; Diana Lucic; Bjørn M. Knudsen; Geir O. Braathen; Hugo de Backer; Rolf Fabian; Hans Fast; Manuel Gil; Esko Kyrö; Ib Steen Mikkelsen; Markku Rummukainen; Johannes Stähelin; Costas Varotsos

1995-01-01

151

Cooling of the Arctic and Antarctic polar stratospheres due to ozone depletion  

SciTech Connect

Long time records of stratospheric temperatures indicate that substantial cooling has occurred during spring over polar regions of both hemispheres. These cooling patterns are coincident with observed recent ozone depletions. Time series of temperature from radiosonde, satellite, and National Centers for Environmental Prediction reanalysis data are analyzed in order to isolate the space-time structure of the observed temperature changes. The Antarctic data show strong cooling (of order 6--10 K) in the lower stratosphere ({approximately} 12--21 km) since approximately 1985. The cooling maximizes in spring (October--December), with small but significant changes extending throughout Southern Hemisphere summer. No Antarctic temperature changes are observed during midwinter. Significant warming is found during spring at the uppermost radiosonde data level (30 mb, {approximately} 24 km). These observed temperature changes are all consistent with model predictions of the radiative response to Antarctic polar ozone depletion. Winter and spring temperatures in Northern Hemisphere polar regions also indicate a strong cooling in the 1990s, and the temperature changes are coherent with observed ozone losses. The overall space-time patterns are similar between both hemispheres, suggesting that the radiative response to ozone depletion is an important component of the Arctic cooling as well.

Randel, W.J.; Wu, F. [National Center for Atmospheric Research, Boulder, CO (United States)

1999-05-01

152

Arctic Expedition of the Frozen Five: an Alternative way of Education and Outreach During the International Polar Year  

NASA Astrophysics Data System (ADS)

In March 2007, a group of international students of the geosciences will embark on a two month expedition across the wilderness of Svalbard. The journey will involve traversing up to 1000 km of high Arctic glaciers between 76° an 80°N, reaching both the southernmost and northernmost capes of Spitsbergen, Svalbard's largest island. We expect to be frequently camping at -30°C, as well as having a high probability of encountering polar bears, crevasses and arctic storms during the expedition. Through this expedition, we wish to promote the multi-disciplinary approach required in successful Arctic science. Our team, young and energetic, has already demonstrated a strong research interest in the Arctic and is ready to share their passion with the general public. Presentations by the various team members focus on the enhanced climate change and related processes witnessed at high latitudes. The concept of alternative energy, including solar power and kites used while en route, is given a high priority throughout. Here we present the education and outreach framework of the project, as well as introducing the research background of the team. We highlight current progress on the integration of this expedition in high schools around the world. The Frozen Five expedition runs in close collaboration with New Zealand's Youth Steering Committee, a major IPY project, aiming to network young polar researchers and promote the study of the polar regions to potential scientists.

Senger, K.; Björkman, M.; Garny, H.; Girard, L.; Lichteneger, J.

2006-12-01

153

Trans-polar observations of the morphological properties of Arctic sea ice  

NASA Astrophysics Data System (ADS)

Numerous ground-based and satellite observations of polar sea ice offer substantial evidence of a reduction in the areal extent and thickness of the Arctic ice cover. During the 2005 Healy-Oden Trans-Arctic Expedition 2005 a trans-Arctic survey of the physical properties of the polar ice pack was conducted. The observational program consisted of four broad classes of snow and ice activities: observations made while the ship was in transit; measurements made at 30 ice stations; 11 helicopter photographic survey flights; and the deployment of autonomous ice mass balance buoys. In transit observations revolved about the ice watch, which reported ice conditions, including ice thicknesses, classes and concentrations of the primary, secondary, and tertiary categories using the ASPECT protocol at two-hour intervals. Pond fractions were large early in the cruise reaching peak values of 0.5 and averaging at 0.25. These large values were concurrent with the southernmost latitudes of the ice pack. Ice concentrations ranged from 0.8 to 1.0 above 79 N, save for an area between 88 30 N and 89 30 N, where a large area of polynyas was observed. Surveys of snow depth and ice thickness were conducted at 23 ice stations along the cruise track, where ice cores and soot were also sampled. Thickness observations suggest a general latitudinal trend of increasing ice thickness moving northward. Thickness surveys showed considerable variability from floe to floe and within a single floe. Average floe thicknesses varied from 1.0 to 2.6 m, and the standard deviation of thickness on an individual floe was as large as one meter. The upper 10 to 12 cm of the ice typically consisted of a loose decomposed surface granular layer overlying a drained layer. The decomposed layer thickness gradually solidified from summer maximum values of 8-10 cm in mid-August to about 1 cm after freezup. The average optical-equivalent soot content was 4 ng soot/g for new snow, 8 for the surface granular layer of MY ice and 17 for the interior of MY ice.

Elder, B. C.; Perovich, D. K.; Grenfell, T. C.; Harbeck, J.; Light, B.; Everhart, K. K.

2006-12-01

154

Attribution of the Arctic ozone column deficit in March 2011  

NASA Astrophysics Data System (ADS)

Arctic column ozone reached record low values (?310 DU) during March of 2011, exposing Arctic ecosystems to enhanced UV-B. We identify the cause of this anomaly using the Oslo CTM2 atmospheric chemistry model driven by ECMWF meteorology to simulate Arctic ozone from 1998 through 2011. CTM2 successfully reproduces the variability in column ozone, from week to week, and from year to year, correctly identifying 2011 as an extreme anomaly over the period. By comparing parallel model simulations, one with all Arctic ozone chemistry turned off on January 1, we find that chemical ozone loss in 2011 is enhanced relative to previous years, but it accounted for only 23% of the anomaly. Weakened transport of ozone from middle latitudes, concurrent with an anomalously strong polar vortex, was the primary cause of the low ozone When the zonal winds relaxed in mid-March 2011, Arctic column ozone quickly recovered.

Isaksen, I. S. A.; Zerefos, C.; Wang, W.-C.; Balis, D.; Eleftheratos, K.; Rognerud, B.; Stordal, F.; Berntsen, T. K.; LaCasce, J. H.; Søvde, O. A.; Olivié, D.; Orsolini, Y. J.; Zyrichidou, I.; Prather, M.; Tuinder, O. N. E.

2012-12-01

155

The Arctic is no longer put on ice: Evaluation of Polar cod ( Boreogadus saida) as a monitoring species of oil pollution in cold waters  

Microsoft Academic Search

The withdrawing Arctic ice edge will facilitate future sea transport and exploration activities in the area, which calls for the establishment of relevant cold water monitoring species. The present study presents first results of field baseline levels for core oil pollution biomarkers in Polar cod (Boreogadussaida) sampled from pristine, Arctic waters. Furthermore, biomarker response levels were characterized in controlled laboratory

Henrik Jonsson; Rolf C. Sundt; Endre Aas; Steinar Sanni

2010-01-01

156

Intralobular Distribution of Vitamin A-Storing Lipid Droplets in Hepatic Stellate Cells with Special Reference to Polar Bear and Arctic Fox  

Microsoft Academic Search

We examined the liver of adult polar bears, arctic foxes, and rats by gold chloride staining, fluorescence microscopy for the detection of autofluorescence of vitamin A, hematoxylin-eosin staining, staining with Masson's trichrome, Ishii and Ishii's silver impregnation, and transmission electron microscopical morphometry. The liver lobules of the arctic animals showed a zonal gradient in the storage of vitamin A. The

Nobuyo Higashi; Katsuyuki Imai; Mitsuru Sato; Takeya Sato; Naosuke Kojima; Mitsutaka Miura; Heidi L Wold; Jan Øivind Moskaug; Trond Berg; Kaare R Norum; Norbert Roos; Kenjiro Wake; Rune Blomhoff; Haruki Senoo

2004-01-01

157

Bacterial diversity in faeces from polar bear (Ursus maritimus) in Arctic Svalbard  

PubMed Central

Background Polar bears (Ursus maritimus) are major predators in the Arctic marine ecosystem, feeding mainly on seals, and living closely associated with sea ice. Little is known of their gut microbial ecology and the main purpose of this study was to investigate the microbial diversity in faeces of polar bears in Svalbard, Norway (74-81°N, 10-33°E). In addition the level of blaTEM alleles, encoding ampicillin resistance (ampr) were determined. In total, ten samples were collected from ten individual bears, rectum swabs from five individuals in 2004 and faeces samples from five individuals in 2006. Results A 16S rRNA gene clone library was constructed, and all sequences obtained from 161 clones showed affiliation with the phylum Firmicutes, with 160 sequences identified as Clostridiales and one sequence identified as unclassified Firmicutes. The majority of the sequences (70%) were affiliated with the genus Clostridium. Aerobic heterotrophic cell counts on chocolate agar ranged between 5.0 × 104 to 1.6 × 106 colony forming units (cfu)/ml for the rectum swabs and 4.0 × 103 to 1.0 × 105 cfu/g for the faeces samples. The proportion of ampr bacteria ranged from 0% to 44%. All of 144 randomly selected ampr isolates tested positive for enzymatic ?-lactamase activity. Three % of the ampr isolates from the rectal samples yielded positive results when screened for the presence of blaTEM genes by PCR. BlaTEM alleles were also detected by PCR in two out of three total faecal DNA samples from polar bears. Conclusion The bacterial diversity in faeces from polar bears in their natural environment in Svalbard is low compared to other animal species, with all obtained clones affiliating to Firmicutes. Furthermore, only low levels of blaTEM alleles were detected in contrast to their increasing prevalence in some clinical and commensal bacterial populations.

2010-01-01

158

A closer look at Arctic ozone loss and polar stratospheric clouds  

NASA Astrophysics Data System (ADS)

The empirical relationship found between column-integrated Arctic ozone loss and the presence of polar stratospheric clouds is updated and examined in more detail. The relationship is found to hold at different altitudes as well as in the column. Analysis of the photochemistry leading to the ozone loss shows that the early winter activation is limited by the photolysis of nitric acid. This step produces nitrogen dioxide which is converted to chlorine nitrate which in turn reacts with hydrogen chloride on any polar stratospheric clouds to form active chlorine. The rate-limiting step is the photolysis of nitric acid: this occurs at the same rate every year and so the interannual variation in the ozone loss is caused by the extent and persistence of the polar stratospheric clouds. In early spring the ozone loss rate increases as the solar insolation increases the photolysis of the chlorine monoxide dimer. However the length of the ozone loss period is determined by the photolysis of nitric acid which also occurs in the near ultraviolet. As a result the amount of the ozone loss is principally limited by the extent of original activation rather than its timing. In addition a number of factors, including the vertical changes in pressure and total inorganic chlorine as well as of de-nitrification and re-nitrification, offset each other. As a result the extent of original activation is the most important factor influencing ozone loss, and the interannual variability is relatively small, as observed. These results indicate that relatively simple parameterisations of polar ozone loss could be developed for use in coupled chemistry climate models.

Lehmann, Ralph; Harris, Neil; Rex, Markus; von der Gathen, Peter

2010-05-01

159

Thinning Arctic Ice Cap as Simulated by the Polar Ice Prediction System (PIPS): 2000-2008.  

National Technical Information Service (NTIS)

Even though the Arctic is one of the most hostile operational environments in the world, numerous vessels transit the Arctic regularly in summer when coastal melting opens the shortest connection between much of the North Atlantic and North Pacific. Free ...

C. N. Barron L. F. Smedstad P. G. Posey R. H. Preller

2009-01-01

160

Lidar observations of stratospheric ozone and aerosol above the Canadian High Arctic during the 1994–95 winter  

Microsoft Academic Search

This letter reports on lidar observations of arctic stratospheric ozone and aerosol made from late December 1994 to mid-March 1995. These observations were conducted at Eureka (80øN,86.42øW) in the dian arctic. Based on NMC potential vorticity data and aerosol observations, the lower stratosphere over Eu- reka was seen to be clearly within the Polar Vortex for most of the observation

D. P. Donovan; J. C. Bird; J. A. Whiteway; T. J. Duck; S. R. Pal; A. I. Carswell

1995-01-01

161

Simultaneous Bro and Oclo Profile Measurements In The Arctic Vortex; Implications For The Clo and Bro Chemistry and Inferred Ozone Loss From The Clo\\/bro Ozone Loss Cycle  

Microsoft Academic Search

During the EuroSolve campaign in winter 1999\\/2000, the LPMA\\/DOAS (Labora- toire de Physique Moleculaire et Applications\\/Differential Optical Absorption Spec- troscopy) balloon was lauched from Kiruna into the highly activated arctic vortex on Feb. 18, 2000. The azimuth-controlled balloon gondola carried three spectrometer, which performed solar occultation measurements in virtually at whole all wavelength from 320 nm into the mid-infrared. Line

M. Dorf; H. Bösch; M. Chipperfield; C. Camy-Peyret; R. Fitzenberger; S. Payan; B. Sinnhuber; F. Weidner; K. Pfeilsticker

2002-01-01

162

NOy from Michelson Interferometer for Passive Atmospheric Sounding on Environmental Satellite during the Southern Hemisphere polar vortex split in September/October 2002  

NASA Astrophysics Data System (ADS)

Reactive nitrogen species HNO3, ClONO2, NO, NO2, and N2O5 were retrieved from high resolution atmospheric limb emission spectra measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board the European Environmental Satellite (ENVISAT) during the split of the southern polar vortex in September/October 2002. The chemical and transport processes determining the NOy deficit and partitioning are investigated here. Most of the available NOy in the polar vortex was in the form of HNO3 and NOx in the lower stratosphere except for the period 22-27 September when NOy was mostly in the form of HNO3 and ClONO2 between the 400 K and 475 K levels. The dominant process throughout the lower stratosphere was enhanced photolysis of HNO3 resulting in a steady increase of NOx during the split of vortex. The enhanced photolysis was initiated following the displacement of the vortex to low and midlatitudes. This observation was confirmed by the buildup of HNO3 after this period in mid-October following the vortex repositioning on the pole. N2O5 inside the vortex increased above the 625 K level during the 22-27 September period following the enhancement of NOx from HNO3 photolysis. On the 475 K level, the NOy volume mixing ratio (VMR) inside the vortex is lower than the reference value derived from its proxy early winter exvortex relation by about 12.5 ppbv during the whole period. The artificial reference linear tracer method suggests that the contribution to the NOy deficit due to quasi-horizontal mixing and denitrification before the split of vortex is approximately 25% and 75%, respectively. After the vortex split the contribution due to mixing increased to 40-45%, while that due to denitrification decreased to 55-60%. The quasi-isentropic mixing line approach uses [CH4]:[N2O] vortex scatterplots to estimate the mixing induced NOy deficit to be 55-60% before, and 62% after, the vortex split.

Mengistu Tsidu, G.; Stiller, G. P.; von Clarmann, T.; Funke, B.; HöPfner, M.; Fischer, H.; Glatthor, N.; Grabowski, U.; Kellmann, S.; Kiefer, M.; Linden, A.; López-Puertas, M.; Milz, M.; Steck, T.; Wang, D. Y.

2005-06-01

163

Mechanisms of Arctic Oscillation response to volcanic aerosols and ozone changes caused by the 1991 Mt. Pinatubo eruption  

Microsoft Academic Search

All strong equatorial volcanic eruptions during the period of instrumental observations have forced a positive phase of the Arctic Oscillation (AO) for one or two years following each eruption. The conventional view is that the volcanic effect on the AO is caused by aerosol heating in the tropical lower stratosphere that produces a stronger polar vortex that prevents the propagation

G. Stenchikov; A. Robock; M. D. Schwarzkopf; V. Ramaswamy; S. Ramachandran

2001-01-01

164

Polar night vortex breakdown and large-scale stirring in the southern stratosphere  

Microsoft Academic Search

The present paper examines the vortex breakdown and large-scale stirring during the final warming of the Southern Hemisphere\\u000a stratosphere during the spring of 2005. A unique set of in situ observations collected by 27 superpressure balloons (SPBs)\\u000a is used. The balloons, which were launched from McMurdo, Antarctica, by the Stratéole\\/VORCORE project, drifted for several\\u000a weeks on two different isopycnic levels

Alvaro de la Cámara; C. R. Mechoso; K. Ide; R. Walterscheid; G. Schubert

2010-01-01

165

Downward transport of upper atmospheric NOx into the polar stratosphere and lower mesosphere during the Antarctic 2003 and Arctic 2002\\/2003 winters  

Microsoft Academic Search

Pronounced upper stratospheric and mesospheric NOx enhancements were measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) in the Southern Hemisphere (SH) polar vortex from May to August 2003, reaching average abundances of 60 ppbv at 50-60 km in July. Peak mixing ratios of around 200 ppbv were measured in the polar night, representing the highest values ever recorded

B. Funke; M. López-Puertas; S. Gil-López; T. von Clarmann; G. P. Stiller; H. Fischer; S. Kellmann

2005-01-01

166

Polar vision or tunnel vision the making of Canadian Arctic waters policy  

Microsoft Academic Search

This article examined the manner by which Canadian maritime Arctic policy is formulated. It suggests that this policy is largely the result of an ad hoc and reactive process. In general, the policy tends to be the product of a specific event initiated by a non-Canadian actor in the Canadian Arctic. In the early 1970s, this event was the voyages

Rob Huebert

1995-01-01

167

On the linkage between tropospheric and Polar Stratospheric clouds in the Arctic as observed by space-borne lidar  

NASA Astrophysics Data System (ADS)

The type of Polar stratospheric clouds (PSCs) as well as their temporal and spatial extent are important for the occurrence of heterogeneous reactions in the polar stratosphere. The formation of PSCs depends strongly on temperature. However, the mechanisms of the formation of solid PSCs are still poorly understood. Recent satellite studies of Antarctic PSCs have shown that their formation can be associated with deep-tropospheric clouds which have the ability to cool the lower stratosphere radiatively and/or adiabatically. In the present study, lidar measurements aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite were used to investigate whether the formation of Arctic PSCs can be associated with deep-tropospheric clouds as well. Deep-tropospheric cloud systems have a vertical extent of more than 6.5 km with a cloud top height above 7 km altitude. PSCs observed by CALIPSO during the Arctic winter 2007/2008 were classified according to their type (STS, NAT, or ice) and to the kind of underlying tropospheric clouds. Our analysis reveals that 172 out of 211 observed PSCs occurred in connection with tropospheric clouds. 72% of these 172 observed PSCs occurred above deep-tropospheric clouds. We also find that the type of PSC seems to be connected to the characteristics of the underlying tropospheric cloud system. During the Arctic winter 2007/2008 PSCs consisting of ice were mainly observed in connection with deep-tropospheric cloud systems while no ice PSC was detected above cirrus. Furthermore, we find no correlation between the occurrence of PSCs and the top temperature of tropospheric clouds. Thus, our findings suggest that Arctic PSC formation is connected to adiabatice cooling, i.e. dynamic effects rather than radiative cooling.

Achtert, P.; Karlsson Andersson, M.; Khosrawi, F.; Gumbel, J.

2012-04-01

168

Differences in mercury bioaccumulation between polar bears (Ursus maritimus) from the Canadian high- and sub-Arctic.  

PubMed

Polar bears (Ursus maritimus) are being impacted by climate change and increased exposure to pollutants throughout their northern circumpolar range. In this study, we quantified concentrations of total mercury (THg) in the hair of polar bears from Canadian high- (southern Beaufort Sea, SBS) and sub- (western Hudson Bay, WHB) Arctic populations. Concentrations of THg in polar bears from the SBS population (14.8 ± 6.6 ?g g(-1)) were significantly higher than in polar bears from WHB (4.1 ± 1.0 ?g g(-1)). On the basis of ?(15)N signatures in hair, in conjunction with published ?(15)N signatures in particulate organic matter and sediments, we estimated that the pelagic and benthic food webs in the SBS are ? 4.7 and ? 4.0 trophic levels long, whereas in WHB they are only ? 3.6 and ? 3.3 trophic levels long. Furthermore, the more depleted ?(13)C ratios in hair from SBS polar bears relative to those from WHB suggests that SBS polar bears feed on food webs that are relatively more pelagic (and longer), whereas polar bears from WHB feed on those that are relatively more benthic (and shorter). Food web length and structure accounted for ? 67% of the variation we found in THg concentrations among all polar bears across both populations. The regional difference in polar bear hair THg concentrations was also likely due to regional differences in water-column concentrations of methyl Hg (the toxic form of Hg that biomagnifies through food webs) available for bioaccumulation at the base of the food webs. For example, concentrations of methylated Hg at mid-depths in the marine water column of the northern Canadian Arctic Archipelago were 79.8 ± 37.3 pg L(-1), whereas, in HB, they averaged only 38.3 ± 16.6 pg L(-1). We conclude that a longer food web and higher pelagic concentrations of methylated Hg available to initiate bioaccumulation in the BS resulted in higher concentrations of THg in polar bears from the SBS region compared to those inhabiting the western coast of HB. PMID:21678897

St Louis, Vincent L; Derocher, Andrew E; Stirling, Ian; Graydon, Jennifer A; Lee, Caroline; Jocksch, Erin; Richardson, Evan; Ghorpade, Sarah; Kwan, Alvin K; Kirk, Jane L; Lehnherr, Igor; Swanson, Heidi K

2011-06-16

169

Discovery of a Water Vapor Layer in the Arctic Summer Mesosphere: Implications for Polar Mesospheric Clouds.  

National Technical Information Service (NTIS)

We report the discovery of a layer of enhanced water vapor in the Arctic summer mesosphere that was made utilizing two new techniques for remotely determining water vapor abundances. The first utilizes Middle Atmosphere High Resolution Spectrograph Invest...

C. R. Englert D. E. Siskind M. E. Summers M. H. Stevens R. R. Conway

2001-01-01

170

Cassini ISS Observations Of The Early Stages Of The Formation Of Titan's South Polar Hood And Vortex In 2012  

NASA Astrophysics Data System (ADS)

Northern spring equinox on Titan occurred on August 11, 2009. In March of 2012 the Imaging Science Subsystem (ISS) on the Cassini spacecraft saw the first evidence for the formation of a polar hood in the atmosphere above Titan’s south pole. Views of the limb showed an optical thickening primarily at about 360 km altitude across a few degrees of latitude centered on the pole. Images of Titan in front of Saturn provide a nearly direct measure of the line-of-sight optical depth as a function of latitude and altitude from about 250 km and higher. Two or more distinct layers are seen, both near the pole and at other latitudes. The highest of these, near 360 km altitude, hosts the embryonic polar hood. On June 27, 2012 ISS observed the pole from high latitude. These images show a distinct and unusual cloudy patch, elongated and not centered on the pole and with an elevated perimeter. The morphology and color indicate an unfamiliar (for Titan) composition and dynamical regime. The interior of the feature consists of concentrations of cloud/haze organized on spatial scales of tens of kilometers. Its morphology is reminiscent of the open cellular convection sometimes seen in the atmospheric boundary layer over Earth’s oceans under conditions of large-scale subsidence. Unlike Earth, where such convection is forced by large surface heat fluxes or the onset of drizzle, convection at 360 km on Titan is more likely to be driven from above by radiative cooling. During the 9 hours we observed Titan, this feature completed a little over one rotation around the pole, providing direct evidence for a polar vortex rotating at a rate roughly consistent with angular-momentum-conserving flow for air displaced from the equator. Part of this work was performed by the Jet Propulsion Laboratory, California Institute of Technology.

West, Robert A.; Del Genio, A.; Perry, J.; Ingersoll, A. P.; Turtle, E. P.; Porco, C.; Ovanessian, A.

2012-10-01

171

Small-scale transport structures in the Arctic winter 2009/2010  

NASA Astrophysics Data System (ADS)

The CRISTA-NF (Cryogenic Infrared Spectrometers and Telescope for the Atmosphere - New Frontiers) instrument is an airborne infrared limb sounder operated aboard the Russian research aircraft M55-Geophysica. The instrument successfully participated in a large Arctic aircraft campaign within the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions) project from January to March 2010 in Kiruna, Sweden. This paper concentrates on the measurements during one flight of the campaign, which took place on 2 March in the vicinity of the polar vortex. We present two-dimensional cross-sections of volume mixing ratios for the trace gases CFC-11, O3, and ClONO2 with an unprecedented vertical resolution of about 500 to 600 m for a large part of the observed altitude range and a dense horizontal sampling along flight direction of ? 15 km. The trace gas distributions show several structures like the polar vortex and filaments composed of air masses of different origin. The situation during the analysed flight is simulated by the chemistry and transport model CLaMS (Chemical Lagrangian Model of the Stratosphere) and compared with the measurements to assess the performance of the model with respect to advection, mixing, and the chemistry in the polar vortex. These comparisons confirm the capability of CLaMS to reproduce even very small-scale structures in the atmosphere. Based on the good agreement between simulation and observation, we use a model concept utilising artificial tracers to further analyse the CRISTA-NF observations in terms of air mass origin. A characteristic of the Arctic winter 2009/10 was a sudden stratospheric warming in early December that led to a split of the polar vortex. The vortex re-established at the end of December. Our passive tracer simulations suggest that large parts of the re-established vortex consisted to about 45% of high- and mid-latitude air.

Kalicinsky, C.; Grooß, J.-U.; Günther, G.; Ungermann, J.; Blank, J.; Höfer, S.; Hoffmann, L.; Knieling, P.; Olschewski, F.; Spang, R.; Stroh, F.; Riese, M.

2013-04-01

172

Flame retardants and methoxylated and hydroxylated polybrominated diphenyl ethers in two Norwegian Arctic top predators: glaucous gulls and polar bears.  

PubMed

The brominated flame retardants have been subject of a particular environmental focus in the Arctic. The present study investigated the congener patterns and levels of total hexabromocyclododecane (HBCD), polybrominated biphenyls, polybrominated diphenyl ethers (PBDEs), as well as methoxylated (MeO) and hydroxylated (OH) PBDEs in plasma samples of glaucous gulls (Larus hyperboreus) and polar bears (Ursus maritimus) from the Norwegian Arctic. The analyses revealed the presence of total HBCD (0.07-1.24 ng/g wet wt) and brominated biphenyl 101 (< 0.13-0.72 ng/g wet wt) in glaucous gull samples whereas these compounds were generally found at nondetectable or transient concentrations in polar bears. Sum (sigma) concentrations of the 12 PBDEs monitored in glaucous gulls (range: 8.23-67.5 ng/g wet wt) surpassed largely those of polar bears (range: 2.65-9.72 ng/g wet wt). Two higher brominated PBDEs, BDE183 and BDE209, were detected, and thus bioaccumulated to a limited degree, in glaucous gulls with concentrations ranging from < 0.03 to 0.43 ng/g wet wt and from < 0.05 to 0.33 ng/g wet wt, respectively. In polar bear plasma, BDE183 was < 0.04 ng/g wet wt for all animals, and BDE209 was only detected in 7% of the samples at concentrations up to 0.10 ng/g wet wt. Of the 15 MeO-PBDEs analyzed in plasma samples, 3-MeO-BDE47 was consistently dominant in glaucous gulls (sigmaMeO-PBDE: 0.30-4.30 ng/g wet wt) and polar bears (sigmaMeO-PBDE up to 0.17 ng/g wet wt), followed by 4'-MeO-BDE49 and 6-MeO-BDE47. The 3-OH-BDE47, 4'-OH-BDE49, and 6-OH-BDE47 congeners were also detected in glaucous gulls (sigmaOH-PBDE up to 1.05 ng/g wet wt), although in polar bears 4'-OH-BDE49 was the only congener quantifiable in 13% of the samples. The presence of MeO- and OH-PBDEs in plasma of both species suggests possible dietary uptake from naturally occurring sources (e.g., marine sponges and green algae), but also metabolically derived biotransformation of PBDEs such as BDE47 could be a contributing factor. Our findings suggest that there are dissimilar biochemical mechanisms involved in PCB and PBDE metabolism and accumulation/elimination and/or OH-PBDE accumulation and retention in glaucous gulls and polar bears. PMID:16173559

Verreault, Jonathan; Gabrielsen, Geir W; Chu, Shaogang; Muir, Derek C G; Andersen, Magnus; Hamaed, Ahmad; Letcher, Robert J

2005-08-15

173

Balloon borne observations of PSCs, Frost Point, ozone and nitric acid in the north polar vortex  

Microsoft Academic Search

A new balloon borne instrument called a backscattersonde has been used to study Polar Stratospheric Clouds (PSCs) at Alert, NWT (82°N, 61.5°W) during January and February of 1989. These measurements were supplemented with frost point, ozone and nitric acid vapor soundings. Type I PSCs were observed at temperatures and pressures generally consistent with present vapor pressure models of HNOâ\\/HâO condensate,

James M. Rosen; S. J. Oltmans; W. F. Evans

1989-01-01

174

Balloon borne observations of PSCs, frost point, ozone and nitric acid in the North Polar vortex  

Microsoft Academic Search

A new balloon-borne instrument called a backscattersonde has been used to study polar stratospheric clouds (PSCs) at Alert, NWT during January and February of 1989. These measurements were supplemented with frost-point, ozone, and nitric-acid-vapor soundings. Type I PSCs were observed at temperatures and pressures generally consistent with present vapor-pressure models of NHO3\\/H2O condensate, but some noticeable inconsistencies exist. It is

James M. Rosen; S. J. Oltmans; W. F. Evans

1989-01-01

175

Balloon borne observations of PSCs, frost point, ozone and nitric acid in the North Polar Vortex  

Microsoft Academic Search

A new balloon borne instrument called a backscattersonde has been used to study Polar Stratospheric Clouds (PSCs) at Alert, NWT (82°N, 61.5°W) during January and February of 1989. These measurements were supplemented with frost point, ozone and nitric acid vapor soundings. Type I PSCs were observed at temperatures and pressures generally consistent with present vapor pressure models of HNO3\\/H2O condensate,

James M. Rosen; S. J. Oltmans; W. F. Evans

1989-01-01

176

Polar vortex dynamics during spring and fall diagnosed using ATMOS trace gas observations  

Microsoft Academic Search

Trace gases measured by the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument dur- ing the Mar\\/Apr 1992 (AT-l), Apr 1993 (AT-2), and Nov 1994 (AT-3) space-shuttle missions have been mapped into equivalent latitude\\/potential temperature (EqL\\/B) coordinates. The asymmetry of the spring vortices results in coverage of subtropical to polar EqLs. EqL\\/B fields of long-lived tracers in spring in both hemispheres show

G. L. Manney; H. A. Michelsen; M. L. Santee; M. R. Gunson; E W. Irion; A. E. Roche; N. J. Livesey

1999-01-01

177

The International Polar Year, 2007-2008, an opportunity to focus on infectious diseases in Arctic regions.  

PubMed

On 3 occasions over the past 125 years, scientists from around the world have worked together to organize scientific and exploration activities in polar regions (www.ipy.org). The first International Polar Year (IPY) in 1881-1884 marked the first major coordinated international scientific initiative to collect standardized meteorological and geophysical data in polar regions. Fifteen expeditions led by 12 nations amassed a large amount of data, but the scientific value was diminished by disjointed publication efforts and lack of long-term institutional commitment; lessons were learned and corrected in subsequent polar years. The second IPY began in 1932. Forty-four nations led expeditions in the Arctic and Antarctic, resulting in greater understanding of the aurora, magnetism, and meteorology. Air and marine navigation, radio operations, and weather forecasting were greatly improved as a result. The third IPY, in 1957-58, was renamed the International Geophysical Year and capitalized on technologic advances developed during World War II. Technologic and scientific momentum was redirected toward research, particularly to studies of the upper atmosphere, a legacy that continues to the present day. Notable achievements included launching the first satellite, measurement of atmospheric greenhouse gases, delineating the system of mid-ocean ridges, and confirming the theory of plate tectonics. PMID:18258069

Parkinson, Alan J

2008-01-01

178

Discovery of a water vapor layer in the Arctic summer mesosphere: Implications for polar mesospheric clouds  

Microsoft Academic Search

We report the discovery of a layer of enhanced water vapor in the Arctic summer mesosphere that was made utilizing two new techniques for remotely determining water vapor abundances. The first utilizes Middle Atmosphere High Resolution Spectrograph Investigation (MAHRSI) OH measurements as a proxy for water vapor. The second is a reanalysis of Halogen Occultation Experiment (HALOE) water vapor data

Michael E. Summers; L. L. Gordley; M. J. McHugh

2001-01-01

179

The Earth Is Faster Now: Indigenous Observations of Arctic Environmental Change. Frontiers in Polar Social Science.  

ERIC Educational Resources Information Center

|This book focuses on documenting and understanding the nature of environmental changes observed by indigenous residents of the Arctic. Common themes include increasing variability and unpredictability of the weather and seasonal climatic patterns, as well as changes in the sea ice and the health of wildlife. Nine papers focus on these changes,…

Krupnik, Igor, Ed.; Jolly, Dyanna, Ed.

180

Environmental constraints on the growth, photosynthesis and reproductive development of Dryas octopetala at a high Arctic polar semi-desert, Svalbard  

Microsoft Academic Search

Opportunities exist in high Arctic polar semidesert communities for colonisation of unvegetated ground by long-lived clonal plants such as Dryas octopetala. This can be achieved by lateral spread of vegetative ramets, or by sexual reproduction and seedling recruitment. The objectives of this study were (1) to determine whether these two means of proliferation show differential sensitivity to contrasting components of

P. A. Wookey; C. H. Robinson; A. N. Parsons; J. M. Welker; T. V. Callaghan; J. A. Lee

1995-01-01

181

Chemical depletion of Arctic ozone in winter 1999/2000  

NASA Astrophysics Data System (ADS)

During Arctic winters with a cold, stable stratospheric circulation, reactions on the surface of polar stratospheric clouds (PSCs) lead to elevated abundances of chlorine monoxide (ClO) that, in the presence of sunlight, destroy ozone. Here we show that PSCs were more widespread during the 1999/2000 Arctic winter than for any other Arctic winter in the past two decades. We have used three fundamentally different approaches to derive the degree of chemical ozone loss from ozonesonde, balloon, aircraft, and satellite instruments. We show that the ozone losses derived from these different instruments and approaches agree very well, resulting in a high level of confidence in the results. Chemical processes led to a 70% reduction of ozone for a region ˜1 km thick of the lower stratosphere, the largest degree of local loss ever reported for the Arctic. The Match analysis of ozonesonde data shows that the accumulated chemical loss of ozone inside the Arctic vortex totaled 117 ± 14 Dobson units (DU) by the end of winter. This loss, combined with dynamical redistribution of air parcels, resulted in a 88 ± 13 DU reduction in total column ozone compared to the amount that would have been present in the absence of any chemical loss. The chemical loss of ozone throughout the winter was nearly balanced by dynamical resupply of ozone to the vortex, resulting in a relatively constant value of total ozone of 340 ± 50 DU between early January and late March. This observation of nearly constant total ozone in the Arctic vortex is in contrast to the increase of total column ozone between January and March that is observed during most years.

Rex, M.; Salawitch, R. J.; Harris, N. R. P.; von der Gathen, P.; Braathen, G. O.; Schulz, A.; Deckelmann, H.; Chipperfield, M.; Sinnhuber, B.-M.; Reimer, E.; Alfier, R.; Bevilacqua, R.; Hoppel, K.; Fromm, M.; Lumpe, J.; Küllmann, H.; KleinböHl, A.; Bremer, H.; von KöNig, M.; Künzi, K.; Toohey, D.; VöMel, H.; Richard, E.; Aikin, K.; Jost, H.; Greenblatt, J. B.; Loewenstein, M.; Podolske, J. R.; Webster, C. R.; Flesch, G. J.; Scott, D. C.; Herman, R. L.; Elkins, J. W.; Ray, E. A.; Moore, F. L.; Hurst, D. F.; Romashkin, P.; Toon, G. C.; Sen, B.; Margitan, J. J.; Wennberg, P.; Neuber, R.; Allart, M.; Bojkov, B. R.; Claude, H.; Davies, J.; Davies, W.; de Backer, H.; Dier, H.; Dorokhov, V.; Fast, H.; Kondo, Y.; Kyrö, E.; Litynska, Z.; Mikkelsen, I. S.; Molyneux, M. J.; Moran, E.; Nagai, T.; Nakane, H.; Parrondo, C.; Ravegnani, F.; Skrivankova, P.; Viatte, P.; Yushkov, V.

2002-10-01

182

Balloon borne observations of PSCs, Frost Point, ozone and nitric acid in the north polar vortex  

SciTech Connect

A new balloon borne instrument called a backscattersonde has been used to study Polar Stratospheric Clouds (PSCs) at Alert, NWT (82{degree}N, 61.5{degree}W) during January and February of 1989. These measurements were supplemented with frost point, ozone and nitric acid vapor soundings. Type I PSCs were observed at temperatures and pressures generally consistent with present vapor pressure models of HNO{sub 3}/H{sub 2}O condensate, but some noticeable inconsistencies exist. It is suggested that these apparent problems, as well as some characteristic peculiarities in the PSC profiles, could be explained by the presence of two phases of the HNO{sub 3}/H{sub 2}O condensate.

Rosen, J.M. (Univ. of Wyoming, Laramie, (USA)); Oltmans, S.J. (NOAA, Boulder, CO (USA)); Evans, W.F.

1989-08-01

183

Arctic technology and policy  

SciTech Connect

Topics covered include: legal regime of the arctic, including national and international legal frameworks that govern arctic resource development; environmental policy and socio-economic issues, focusing on the political and economic considerations of LNG transport in icebound waterways; risk and safety assessment for arctic offshore projects, drilling systems for the arctic; arctic offshore technology, including island, steel, and concrete structures; icebreaking technology, focusing on the current state of the art and indicating future research areas; arctic oceanography, summarizing characteristics of ice from field experiments pertaining to the design of structures, ships, and pipelines; arctic seismic exploration, detailing signal processes for underwater communication in the context of arctic geology and geophysics; ice morphology, providing information about ice shapes, particularly critical to the determination of overall strength of ice masses; remote sensing; modeling of arctic ice fields, including information about the design and construction of offshore facilities in polar areas; and engineering properties of ice, providing theoretical and experimental studies.

Dyer, I.; Chryssostomidis, C.

1984-01-01

184

Heterogeneous formation of polar stratospheric clouds-nucleation of nitric acid trihydrate (NAT) in the arctic stratosphere  

NASA Astrophysics Data System (ADS)

Satellite based observations during the Arctic winter of 2009/2010 provide firm evidence that, in contrast to the current theory, the nucleation of nitric acid trihydrate (NAT) in the polar stratosphere does not only occur on preexisting ice particles. In order to explain the NAT clouds observed over the Arctic in mid December 2009, a heterogeneous nucleation mechanism is required, occurring on the surface of dust or meteoritic particles. For the first time, a detailed microphysical modelling of this NAT formation pathway has been carried out. Heterogeneous NAT formation was calculated along tens of thousands of trajectories, ending at Cloud Aerosol Lidar with Orthogonal Polarisation (CALIOP) observation points. Comparing the optical properties of the modelled NAT PSCs with these observations enables the thorough validation of a newly developed NAT nucleation parameterisation, which has been built into the Zurich Optical and Microphysical box Model (ZOMM). The parameterisation is based on active site theory and is simple to implement in models. It is shown that the new method is capable of reproducing observed PSCs very well, despite the varied conditions experienced by air parcels travelling along the different trajectories.

Hoyle, C. R.; Engel, I.; Luo, B. P.; Pitts, M. C.; Poole, L. R.; Grooß, J.-U.; Peter, T.

2013-05-01

185

Vortex polarization, strain induced phase transitions and dielectric response in ultra-thin PbTiO3 nanowires from first principles  

NASA Astrophysics Data System (ADS)

Nature of ferroelectricity in nanostructures and the resulting dielectric response are of both fundamental and applied interest. Here, using density functional theory (DFT) based computations, we investigate polarization configurations as a function of axial strain in ultra-thin PbTiO3 [001] nanowires. Our computations involved relaxed and axially strained free-standing nanowires with varying sidewall terminations and diameters. While stress-free nanowires with their sidewalls terminated by PbO surfaces displayed purely rectilinear axial polarization at all sizes, the TiO2-terminated nanowires, at a critical diameter of 16 å, display a non-rectilinear vortex polarization transverse to the nanowire axis. We discuss the origins of such behavior. We also predict the existence of novel stress-induced phase transitions between the mutually exclusive vortex and the axial polarization states in both the PbO- and TiO2-terminated nanowires. Normal mode vibrational frequency analysis of these nanowires further confirms these results. Furthermore, by employing density functional perturbation theory in combination with effective medium dielectric theory we calculate dielectric permittivity of the ferroelectric nanowires and compare it with the corresponding bulk results.

Pilania, Ghanshyam; Ramprasad, R.

2012-02-01

186

Oceanographic Aspects of Recent Changes in the Arctic  

NASA Astrophysics Data System (ADS)

In the Arctic recent decadal-scale changes have marked the atmosphere, ocean, and land. Connections between the oceanographic changes and large-scale atmospheric circulation changes are emerging. Surface atmospheric pressure has shown a declining trend over the Arctic. In the 1990s, the Arctic Ocean circulation took on a more cyclonic character, and the front separating Atlantic-derived waters of the Eurasian Basin and the Pacific-derived waters of the Canadian Basin shifted counterclockwise. The temperature of Atlantic water in the Arctic Ocean reached record levels. The cold halocline, which isolates the surface from the warm Atlantic water, grew thinner disappearing entirely from the Amundsen Basin at one point [Steele and Boyd, 1998]. Arctic sea ice extent has decreased 3% per decade since the 1970s [Parkinson et al., 1999]. Sea ice thickness over much of the Arctic decreased 43% between 1958-1976 and 1993-1997 [Rothrock et al., 1999]. Arctic ecosystems have responded to these changes. Sea ice studies in the late 1990s indicate that the sea ice algal species composition changed from decades before, with the species recently being characterized by more brackish and freshwater forms. Barents Sea fisheries have shifted north following reductions in ice extent. Pacific salmon species have been found entering rivers in the Arctic. There is evidence that this complex of pan-Arctic changes is connected with the rising trend in the Arctic Oscillation (AO) or Northern Hemisphere atmospheric polar vortex in the 1990s. Theoretical evidence that a positive trend in the AO index might be indicative of greenhouse warming raises the possibility that the recent complex of changes is an Arctic characteristic of global climate change. Also, the changes in ice cover manifest a connection between the complex of change and global climate through ice-albedo feedback, by which reductions in ice cover reduce the amount of sunlight reflected from the earth's surface. Another important climate feedback is that the changes in ocean circulation and ice production have increased the amount of relatively fresh surface water exported to the sub-Arctic Seas, increasing stratification there, and arguably reducing the strength of the global thermohaline circulation. Since the mid-1990s the strength of the Polar Vortex (AO) has relaxed partially toward earlier levels. Recent observations show that Arctic Ocean water mass structure has relaxed somewhat towards climatology near the surface but is still changing at depth. The cold halocline has recovered in some areas. This reinforces the notion that the changes in the Arctic are tied to the atmospheric circulation of the whole northern hemisphere. The events of the last 10-15 years suggest ways the Arctic environment may be an indicator and agent of climate change and highlight the importance of a systematic program to observe the changing Arctic. References Parkinson C. L., D. J. Cavalieri, P. Gloersen, H. J. Zwally, and J. C. Comiso, 1999, Arctic sea ice extents, areas, and trends, 1978-1996, J. Geophys. Res., 104, 20,387-20,856. Rothrock, D. A., Y. Yu, and G. A. Maykut, 1999, Thinning of the Arctic sea-ice cover, Geophys. Res. Lett., 26(23), 3469-3472. Steele, M., and T. Boyd, 1998, Retreat of the cold halocline layer in the Arctic Ocean, J. Geophys. Res., 103, 10,419-10,435.

Morison, J. H.

2002-12-01

187

Accuracy of Arctic stratospheric temperature analyses and the implications for the prediction of polar stratospheric clouds  

Microsoft Academic Search

Lower stratospheric temperature analyses from European Centre for Medium-Range Weather Forecasts (ECMWF) are compared with radiosonde temperatures in the Arctic in the winters 1994\\/95 and 1995\\/96. In February and March 1996, the biases between mean layer radiosonde and ECMWF temperatures are ?0.1±1.2, 0.0±1.1, +0.1±1.4, and ?0.7±1.8 K at 100, 70, 50, and 30 mb, respectively. Individual measurements between the radiosonde

Bjørn M. Knudsen

1996-01-01

188

Accuracy of arctic stratospheric temperature analyses and the implications for the prediction of polar stratospheric clouds  

Microsoft Academic Search

Lower stratospheric temperature analyses from European Centre for Medium-Range Weather Forecasts (ECMWF) are compared with radiosonde temperatures in the Arctic in the winters 1994\\/95 and 1995\\/96. In February and March 1996, the biases between mean layer radiosonde and ECMWF temperatures are -0.1+\\/-1.2, 0.0+\\/-1.1, +0.1+\\/-1.4, and -0.7+\\/-1.8 K at 100, 70, 50, and 30 mb, respectively. Individual measurements between the radiosonde

Bjørn M. Knudsen

1996-01-01

189

Climate Change and Arctic Ecosystems  

NSDL National Science Digital Library

In this activity, students learn about how climate change is affecting the Arctic ecosystem and then investigate how this change is impacting polar bear populations. Students analyze maps of Arctic sea ice, temperature graphs, and polar bear population data to answer questions about the impact of climate change on the Arctic ecosystem.

Change, Project A.; University, Purdue

190

Vortex structures in dipolar condensates  

SciTech Connect

We investigate the properties of single vortices and of the vortex lattice in a rotating dipolar condensate. We show that vortices in this system possess several features induced by the long-range anisotropic dipolar interaction between particles. For example, when the dipoles are polarized along the rotation axis, vortices may display a craterlike structure; when dipoles are polarized orthogonal to the rotation axis, the vortex cores take an elliptical shape and the vortex lattice no longer possesses hexagonal symmetry.

Yi, S. [Department of Physics and Astronomy and Rice Quantum Institute, Rice University, Houston, Texas 77251-1892 (United States); Institute of Theoretical Physics, Chinese Academy of Science, Beijing, 100080 (China); Pu, H. [Department of Physics and Astronomy and Rice Quantum Institute, Rice University, Houston, Texas 77251-1892 (United States)

2006-06-15

191

Final warming of the Southern Hemisphere polar vortex in high- and low-top CMIP5 models  

NASA Astrophysics Data System (ADS)

The final warming date of the polar vortex is a key component of Southern Hemisphere stratospheric and tropospheric variability in spring and summer. We examine the effect of external forcings on Southern Hemisphere final warming date and the sensitivity of any projected changes to model representation of the stratosphere. Final warming date is calculated using a temperature-based diagnostic for ensembles of high- and low-top models from the fifth Coupled Model Intercomparison Project (CMIP5), under the historical, Representative Concentration Pathway (RCP4.5) and RCP8.5 forcing scenarios. The final warming date in the models is generally too late in comparison with those from reanalyses: around 2 weeks too late in the low-top ensemble, and around 1 week too late in the high-top ensemble. Ensemble Empirical Mode Decomposition (EEMD) is used to analyze past and future change in final warming date. Both the low- and high-top ensemble show characteristic behavior expected in response to changes in greenhouse gas and stratospheric ozone concentrations. In both ensembles, under both scenarios, an increase in final warming date is seen between 1850 and 2100, with the latest dates occurring in the early twenty-first century, associated with the minimum in stratospheric ozone concentrations in this period. However, this response is more pronounced in the high-top ensemble. The high-top models show a delay in final warming date in the late 21st century in RCP8.5 that is not produced by the low-top models, which are shown to be less responsive to greenhouse gas forcing. This suggests that it may be necessary to use stratosphere resolving models to accurately predict Southern Hemisphere surface climate change.

Wilcox, L. J.; Charlton-Perez, A. J.

2013-03-01

192

The Arctic Coastal Plain, Alaska  

NSDL National Science Digital Library

This tutorial is about the Arctic tundra biome; the plants and animals found there; and the amount of sunlight, temperatures, seasons and permafrost. Examples of Arctic ecosystem interactions, food chains, and biological adaptations to the Arctic Coastal Plain are given. There are photographs of wolves, caribou, arctic hares, minks, lemmings, arctic foxes, polar bears, seals, walruses, ptarmigans, hawks, and owls. Definitions of ecosystem terms can be found by clicking on the term within the tutorial.

193

Ice navigation studies in the Alaskan Arctic using POLAR Class icebreakers  

Microsoft Academic Search

The operational capability of the U.S. Coast Guard's POLAR Class icebreakers is reviewed for Alaskan ice covered waters. Operational capability is defined in terms of three distinct geographic areas: the Bering, Chukchi, and Beaufort Seas. POLAR Class icebreakers have successfully operated in each of these areas since 1979. As a result of the deployments, it is possible to draw conclusions

L. Brigham; R. Voelker

1985-01-01

194

The polar bear in the room: diseases of poverty in the Arctic  

PubMed Central

In the face of global warming, budgetary austerity and impoverished Arctic residents, the nations of the circumpolar region are presented with a number of difficult choices regarding the provision of health care to the far-flung and isolated regions of their northernmost provinces. Complicating that picture is the reality of neglected tropical diseases in areas far from their perceived normal equatorial range as well as endemic food-borne diseases, including protozoan and helminth parasites, respiratory and gastrointestinal diseases and vaccine-preventable illnesses. This paper discusses the problems of caring for the health and well-being of indigenous populations suffering from extreme poverty, isolation and discrimination in the circumpolar region. After presenting difficulties as supported by the extant literature, the paper continues by suggesting solutions that include novel telenursing applications, targeted distance-educational programs and local community-based health care assistant (HCA) vocational training. These programs will provide cost-effective care that increases life-spans, improves quality of life and provides opportunities to distressed populations in isolated rural communities of the Far North. The toolkit presented in the paper is intended to spur discussion on community health programs that could be adopted to provide proper and humane care for marginalized Arctic populations in an extreme and rapidly changing environment.

Nelson, Chris

2013-01-01

195

In-Situ Measurements of BrO in the early 2011/2012 Arctic Polar Vortex  

NASA Astrophysics Data System (ADS)

The Bromine Monoxide radical was measured along with Chlorine Monoxide with the HALOX instrument during two flights of the M55-Geophysica high-altitude research aircraft from Kiruna (Sweden) employing the Chemical Conversion Resonance Fluorescence (CCRF) Technique, first demonstrated on aircraft by Brune et al., 1989. In the effort to narrow down the remaining uncertainties for the inorganic Bromine loading (Bry) of the stratosphere, In-Situ BrO data provide valuable information, as BrO is the most abundant inorganic Bromine species in sunlit stratospheric air. The BrO detection limit was lowered by recent modifications of the optical setup in the HALOX instrument aiming at the reduction of stray light. However a closer look at the stray light problem also revealed the need for an improved instrument calibration. A concept for a reliable calibration was developed. The new method will be applied to the new dataset and compared to the former calibration. The results from the acquired BrO data along the flight track will be discussed and compared to earlier measurements. Based on the demonstrated field performance the potential of the CCRF technique to quantify the extremely low BrO concentrations in the UTLS and TTL regions in future tropical field measurements will be evaluated. Brune, W. H., J. G. Anderson, and K. R. Chan (1989), In Situ Observations of BrO Over Antarctica: ER-2 Aircraft Results From 54°S to 72°S Latitude, J. Geophys. Res., 94(D14), 16,639-16,647, doi:10.1029/JD094iD14p16639.

Heinecke, F.; Afchine, A.; von Hobe, M.; Richter, A.; Schönfeld, A.; Steinert, C.; Suminska, O.; Tan, V.; Stroh, F.

2012-04-01

196

Size distributions of dicarboxylic acids and inorganic ions in atmospheric aerosols collected during polar sunrise in the Canadian high Arctic  

NASA Astrophysics Data System (ADS)

Size-segregated atmospheric aerosols (11 stages separating particles from <0.04 to >14.2 ?m) collected in the Arctic during the polar sunrise at Alert were analyzed for aerosol mass, dicarboxylic acids, and major inorganic ions. Oxalic, malonic, succinic, and glutaric acids were detected in all size ranges, with oxalic acid being dominant. Their concentrations maximized in the accumulation mode either at 0.24-0.40 or 0.40-0.8 ?m aerodynamic diameters, suggesting that diacids were mainly formed by gas-to-particle conversion via photochemical oxidation of nonmethane hydrocarbons and oxygenated organics originated from continental pollution sources. The relative abundances of oxalic acid were higher in the 0.24- to 0.4-?m size particles (73-78%) than in supermicrometer particles (40-60%), indicating that oxalic acid is produced by gas phase oxidation of precursors followed by accumulation on preexisting particles. Mass size distributions of NH4+ and SO42- peaked in the accumulation mode similar to those of small diacids. The sea-salt enrichment factor of K+ (biomass burning tracer) relative to Na+ maximized in 0.1- to 0.8-?m sizes, whereas those of Mg2+ and Ca2+ (dust tracers) in 0.4- to 7.8-?m particles. Maximized chlorine loss and bromine enrichment were found at 0.4-0.8 and 0.24-0.4 ?m sizes, respectively. Concentrations of Br-, which typically showed a submicrometer maximum, increased significantly during an O3 depletion event having a shift of size distribution to a supermicrometer mode. During this event, oxalic acid concentration relative to succinic acid increased in submicrometer mode (0.24-0.4 ?m), adding to a growing body of evidence supporting the hypothesis that halogen chemistry is important in the production and loss of oxalic acid in the arctic atmosphere.

Kawamura, Kimitaka; Narukawa, Masahiro; Li, Shao-Meng; Barrie, Leonard A.

2007-05-01

197

Such Low Temperatures in the Arctic Region: How Can the Polar Bears Call It Home?  

ERIC Educational Resources Information Center

|Presents an activity on polar bears that integrates language arts and science. Teaches the characteristics of organisms and how distinct environments support distinct organisms. Uses both mathematics and science skills and targets students at the K-4 grade level. (YDS)|

Pringle, Rose M.

2002-01-01

198

Arctic microbial ecosystems and impacts of extreme warming during the International Polar Year  

Microsoft Academic Search

As a contribution to the International Polar Year program MERGE (Microbiological and Ecological Responses to Global Environmental change in polar regions), studies were conducted on the terrestrial and aquatic microbial ecosystems of northern Canada (details at: http:\\/\\/www.cen.ulaval.ca\\/merge\\/). The habitats included permafrost soils, saline coldwater springs, supraglacial lakes on ice shelves, epishelf lakes in fjords, deep meromictic lakes, and shallow lakes,

Warwick F. Vincent; Lyle G. Whyte; Connie Lovejoy; Charles W. Greer; Isabelle Laurion; Curtis A. Suttle; Jacques Corbeil; Derek R. Mueller

2009-01-01

199

Interhemispheric Differences in Polar Stratospheric HNO_3, H_2O, CIO, and O_3  

NASA Astrophysics Data System (ADS)

Simultaneous global measurements of nitric acid (HNO_3), water (H_2O), chlorine monoxide (CIO), and ozone (O_3) in the stratosphere have been obtained over complete annual cycles in both hemispheres by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite. A sizeable decrease in gas-phase HNO_3 was evident in the lower stratospheric vortex over Antarctica by early June 1992, followed by a significant reduction in gas-phase H_2O after mid-July. By mid-August, near the time of peak CIO, abundances of gas-phase HNO_3 and H_2O were extremely low. The concentrations of HNO_3 and H_2O over Antarctica remained depressed into November, well after temperatures in the lower stratosphere had risen above the evaporation threshold for polar stratospheric clouds, implying that denitrification and dehydration had occurred. No large decreases in either gas-phase HNO_3 or H_2O were observed in the 1992-1993 Arctic winter vortex. Although CIO was enhanced over the Arctic as it was over the Antarctic, Arctic O_3 depletion was substantially smaller than that over Antarctica. A major factor currently limiting the formation of an Arctic ozone "hole" is the lack of denitrification in the northern polar vortex, but future cooling of the lower stratosphere could lead to more intense denitrification and consequently larger losses of Arctic ozone.

Santee, M. L.; Read, W. G.; Waters, J. W.; Froidevaux, L.; Manney, G. L.; Flower, D. A.; Jarnot, R. F.; Harwood, R. S.; Peckham, G. E.

1995-02-01

200

Interhemispheric Differences in Polar Stratospheric HNO3, H2O, CIO, and O3.  

PubMed

Simultaneous global measurements of nitric acid (HNO(3)), water (H(2)O), chlorine monoxide (CIO), and ozone (O(3)) in the stratosphere have been obtained over complete annual cycles in both hemispheres by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite. A sizeable decrease in gas-phase HNO(3) was evident in the lower stratospheric vortex over Antarctica by early June 1992, followed by a significant reduction in gas-phase H(2)O after mid-July. By mid-August, near the time of peak CIO, abundances of gas-phase HNO(3) and H(2)O were extremely low. The concentrations of HNO(3) and H(2)O over Antarctica remained depressed into November, well after temperatures in the lower stratosphere had risen above the evaporation threshold for polar stratospheric clouds, implying that denitrification and dehydration had occurred. No large decreases in either gas-phase HNO(3) or H(2)O were observed in the 1992-1993 Arctic winter vortex. Although CIO was enhanced over the Arctic as it was over the Antarctic, Arctic O(3) depletion was substantially smaller than that over Antarctica. A major factor currently limiting the formation of an Arctic ozone "hole" is the lack of denitrification in the northern polar vortex, but future cooling of the lower stratosphere could lead to more intense denitrification and consequently larger losses of Arctic ozone. PMID:17813911

Santee, M L; Read, W G; Waters, J W; Froidevaux, L; Manney, G L; Flower, D A; Jarnot, R F; Harwood, R S; Peckham, G E

1995-02-10

201

POLAR-PALOOZA Polar Researchers and Arctic Residents Engage, Inform and Inspire Diverse Public Audiences by sharing Polar Science and Global Connections during the International Polar Year, using a New Model of Informal Science Education  

NASA Astrophysics Data System (ADS)

(Please note that the POLAR-PALOOZA initiative described in this Abstract is-as of 9/7/2006-"pending" for possible support from NSF and NASA as part of this year's IPY solicitation. Subject to decisions expected by 9/30, this presentation would either be withdrawn, or amplified with specific participants, locations and dates.) Despite the success of well-regarded movies like "March of the Penguins", the polar regions remain a great unknown for most people. Public knowledge about the Arctic and Antarctic, and the critical role of the Poles in the entire Earth system, is nonexistent, incomplete or burdened with misperceptions. The International Polar Years of 2007-2009-and associated "I*Y" science years such as IHY, IYPE and eGY-present a unique opportunity to change this. The people who can best effect this change are those who know the Poles best, through living or working there. Based on innovative but proven models, POLAR-PALOOZA will use three complementary strategies to engage, inform and inspire large public audiences. (1) A national tour, under the working title "Stories from a Changing Planet", will include in-person presentations at science centers, museums, libraries and schools across North America, including Canada and Mexico. The presentations will be augmented by High Definition Video taped on location at the Poles, audio and video podcasts, and special education and outreach activities for targeted audiences. "Stories from a Changing Planet" will provide diverse audiences with an exciting opportunity to meet and interact directly with polar experts, and to appreciate why the Poles and the research done there are directly relevant to their lives. (2) The "HiDef Video Science Story Capture Corps" is a team of professional videographers, using the latest generation of low-cost, high-quality cameras, deployed to both Poles. They will document the work of multiple researchers and projects, rather than focusing on one topic for a single broadcast program. The resulting HD footage will be cataloged, archived and made available as public domain material, accessible to government research agencies for media releases, to the researchers and their home universities, and to science centers and museums. (3) POLAR- PALOOZA will edit short video and audio podcasts from this archive, and distribute them non-exclusively through an open network of websites, including iTunes, YouTube, Google, Yahoo, and the official IPY, US-IPY, NSF and NASA websites. Project design targets underserved groups and regions, and has developed a detailed strategy by which to reach out to under-served minorities and mid-sized and smaller communities over the entire two years of IPY. A balanced cadre of researchers, both male and female, young and old, ethnically-diverse and representing the many disciplines engaged in polar research, has already been identified, and over twenty five scientists, engineers, artists and journalists have committed to participating. The project's Advisors include members of the National Academy's Polar Research Board, and the two U.S. representatives to the international IPY Education and Outreach Committee.

Haines-Stiles, G.; Akuginow, E.

2006-12-01

202

The Severe Arctic Ozone Depletion 2010/11 - Implications for UV Radiation in Europe and North America  

NASA Astrophysics Data System (ADS)

The Arctic winter 2010/11 saw record ozone depletion in the northern polar vortex with column ozone dropping below 250 DU by the end of the winter. One question of concern is, how strongly such a winter affects surface UV radiation in high and mid-latitudes and in particular in central Europe and North America. This obviously depends not only on the degree of ozone depletion but also on the spatial extent and the position of the depleted vortex. Besides, surface UV levels are influenced by other factors such as cloudiness, aerosol loading and variations in the solar flux. Here, monthly average as well as maximum erythemal UV doses are calculated for spring and early summer over different regions in Europe and North America for Arctic winters between 1980 and 2011, using data from the Ozone Monitoring Instrument (OMI) onboard the EOS Aura satellite and the Total Ozone Mapping Spectrometer onboard Nimbus-7, Meteor-3 and Earth-Probe. The comparison of UV data from Arctic winters with very different degrees of polar vortex ozone loss allows to estimate the extent, to which large vortex ozone losses translate directly into higher surface UV in certain areas in high and mid-latitudes. Special attention is given to the 2010/11 winter.

von Hobe, M.; Griessbach, S.; Wegner, T.

2011-12-01

203

FTIR measurements of HF, N{sub 2}O and CFCs during the Arctic polar night with the moon as light source, subsidence during winter 1992/93  

SciTech Connect

The author presents ground based measurements of HF, N{sub 2}O, CFC-12 (CF{sub 2}Cl{sub 2}) and CFC-22 (CHF{sub 2}Cl) vertical distributions from the Arctic winter. These long lived trace atmospheric gases can serve as tracers for atmospheric circulation studies, and here the authors analyze the data to obtain information on the vertical circulation in the atmosphere during the polar winter.

Notholt, J. [Alfred Wegener Institut fuer Polar und Meeresforschung, Potsdam (Germany)

1994-11-01

204

Geographical distribution and identification of methyl sulphone PCB and DDE metabolites in pooled polar bear ( Ursus maritimus) adipose tissue from western hemisphere Arctic and Subarctic regions  

Microsoft Academic Search

The geographical distribution of methyl sulphone (MeSO2-) PCB and DDE metabolites is unknown for any species in any region. In this study, pooled male polar bear (Ursus maritimus) adipose samples from 12 arctic and subarctic regions from the Bering Sea to the Greenland Sea were analyzed for PCBs, DDE, and their MeSO2-metabolites. Each adipose pool contained from three to 27

Robert J. Letcher; Ross J. Norstrom

1995-01-01

205

Thickness and surface-properties of different sea-ice regimes within the Arctic Trans Polar Drift: Data from summers 2001, 2004 and 2007  

Microsoft Academic Search

Large-scale sea-ice thickness and surface property data were obtained in three summers and in three different sea-ice regimes in the Arctic Trans-Polar Drift (TPD) by means of helicopter electromagnetic sounding. Distribution functions P of sea-ice thickness and of the height, spacing, and density of sails were analyzed to characterize ice regimes of different ages and deformations. Results suggest that modal

L. Rabenstein; S. Hendricks; T. Martin; A. Pfaffhuber; C. Haas

2010-01-01

206

An analysis of large HNO3-containing particles sampled in the Arctic stratosphere during the winter of 1999\\/2000  

Microsoft Academic Search

Large (>2 ?m diameter) HNO3-containing polar stratospheric cloud (PSC) particles were measured in situ by the NOAA NOy instrument on board the NASA ER-2 aircraft during seven flights in the 1999\\/2000 Arctic winter vortex. Here we discuss the detection of these large PSC particles, their spatial distribution, the ambient conditions under which they were detected, and our methods for interpreting

M. J. Northway; R. S. Gao; P. J. Popp; J. C. Holecek; D. W. Fahey; K. S. Carslaw; M. A. Tolbert; L. R. Lait; S. Dhaniyala; R. C. Flagan; P. O. Wennberg; M. J. Mahoney; R. L. Herman; G. C. Toon; T. P. Bui

2002-01-01

207

An analysis of large HNO3-containing particles sampled in the Arctic stratosphere during the winter of 1999\\/2000  

Microsoft Academic Search

Large (>2 mum diameter) HNO3-containing polar stratospheric cloud (PSC) particles were measured in situ by the NOAA NOy instrument on board the NASA ER-2 aircraft during seven flights in the 1999\\/2000 Arctic winter vortex. Here we discuss the detection of these large PSC particles, their spatial distribution, the ambient conditions under which they were detected, and our methods for interpreting

M. J. Northway; R. S. Gao; P. J. Popp; J. C. Holecek; D. W. Fahey; K. S. Carslaw; M. A. Tolbert; L. R. Lait; S. Dhaniyala; R. C. Flagan; P. O. Wennberg; M. J. Mahoney; R. L. Herman; G. C. Toon; T. P. Bui

2002-01-01

208

Chemical Ozone Loss and Chlorine Activation Deduced From HALOE and OMS Measurements in Arctic Winter 1999-2000  

NASA Astrophysics Data System (ADS)

We employ observations from HALOE and from balloon-borne instruments (on OMS-remote, OMS in-situ, and Triple) to investigate ozone loss in the stratosphere in the vortex in Arctic winter 1999-2000. Using HF and CH4 as a long-lived tracer, we identify chemical ozone destruction and chlorine activation in the polar vortex. Reference relations, relevant for chemically undisturbed ``early vortex'' conditions are derived from the OMS-remote and in-situ balloon measurements on 19 November and 3 December 1999. Deviations from this ``early vortex'' reference are caused by chemical ozone loss and heterogeneous chlorine activation. The observations indicate severe chemical ozone loss, with a maximum loss of over 60% locally in the lower stratosphere (465-415 K) by mid-March 2000. The average loss in column ozone between 380-550 K, (deep) inside the vortex, in mid-March amounts to about 85 +/- 10 DU. The findings for winter 1999-2000 are put into perspective of Arctic ozone loss deduced from HALOE measurements in earlier cold winters (e.g., 1992-1993, 1994-1995, and 1996-1997). These winters have been reanalysed using the most recent HALOE data version. Further, additional observations were taken into account to investigate the validity of the reference relation for chemically unperturbed conditions in the early vortex.

Mueller, R.; Tilmes, S.; Grooss, J.; McKenna, D. S.; McKenna, D. S.; Mueller, M.; Toon, G. C.; Stachnik, R. A.; Margitan, J. J.; Elkins, J. W.; James, R. M.

2001-12-01

209

IMMOBILIZATION OF POLAR BEARS (URSUS MARITIMUS) WITH TELAZOL#{174} IN THE CANADIAN ARCTIC  

Microsoft Academic Search

In 1986, 213 polar bears (Ursus maritimus) were immobilized with Telazol#{174} on the sea ice of the eastern Beaufort Sea during April and May, and 106 along the western coast of Hudson Bay near Churchill, Manitoba (Canada) in September. No animals died from handling. The efficacy of this drug at different seasons and the physiological responses of the immobilized bears

I. Stirling; C. Spencer; D. Andriashek

1989-01-01

210

Detection of temperatures conducive to Arctic polar stratospheric clouds using CHAMP and SAC-C radio occultation data  

NASA Astrophysics Data System (ADS)

We use global positioning system radio occultation (GPSRO) data from the Challenging Mini-Satellite Payload for Geophysical Research and Application (CHAMP) and Satélite de Applicaciones Científicas-C (SAC-C) low Earth orbiting satellites to investigate the occurrence of air with temperatures cold enough to allow the formation of polar stratospheric clouds (PSCs) during four successive Arctic winters spanning 2001 to 2005. The GPSRO data are validated and compared with analysis data from the European Centre for Medium-Range Weather Forecasts using a series of criteria designed to eliminate faulty soundings but retain profiles which do not differ too strongly from the model data. We find that GPSRO is able to detect more PSC-prone temperature profiles during winters with disturbed conditions (in particular during December 2001 and 2003) than the analysis, but that the model fully captures the extent of PSC-prone air in winters with strong, cold vortices (in particular December 2002 and January 2005). Examination of detailed profiles for December 2001 shows that this difference is due to the ability of GPSRO to detect short-vertical wavelength features which may represent either localized gravity or global-scale planetary waves. Since the GPSRO data are now being directly assimilated into operational analysis systems, the benefits of the higher vertical resolution retrievals it provides should become evident in future observational studies of PSC formation and ozone loss, particularly under the disturbed conditions noted in several recent winters.

de La Torre JuáRez, M.; Marcus, S.; DöRnbrack, A.; Schrøder, T. M.; Kivi, R.; Iijima, B. A.; Hajj, G. A.; Mannucci, A. J.

2009-04-01

211

A polar low embedded in a blocking high over the Pacific Arctic  

NASA Astrophysics Data System (ADS)

A polar low (PL) is a short-lived phenomenon involving strong winds that occurs over polar oceans. In October 2009, the R/V Mirai encountered a PL with a 600-km-wide, comma-shaped cloud that developed over the Chukchi Sea. A shipboard Doppler radar and radiosondes were used to understand the fine structure of this PL. Analyses of low-level winds and the thermodynamic structure indicated that the development of the PL was decoupled from sea surface thermal forcing. The PL was likely triggered by an intrusion of a potential vorticity (PV) anomaly at the tropopause. A southerly warm advection associated with a blocking high over Alaska resulted in rapid development of the PL in front of the cold dome induced by the upper-level PV anomaly. The westerly winds after passage of the PL seemed to modify the upper-ocean structure dramatically.

Inoue, Jun; Hori, Masatake E.; Tachibana, Yoshihiro; Kikuchi, Takashi

2010-07-01

212

Relative influences of atmospheric chemistry and transport on Arctic ozone trends  

NASA Astrophysics Data System (ADS)

The reduction in the amount of ozone in the atmospheric column over the Arctic region, observed during the 1990s,, resembles the onset of the Antarctic ozone `hole' in the mid-1980s, but the two polar regions differ significantly with respect to the relative contributions of chemistry and atmospheric dynamics to the ozone abundance. In the strong, cold Antarctic vortex, rapid springtime chemical ozone loss occurs throughout a large region of the lower stratosphere, whereas in the Arctic, although chemical ozone depletion has been observed,,,,,,,,, the vortex is generally much smaller, weaker and more variable. Here we report a model-based analysis of the relative importance of dynamics and chemistry in causing the Arctic ozone trend in the 1990s, using a state-of-the-art three-dimensional stratospheric chemistry-transport model. North of 63°N we find that, on average, dynamical variations dominate the interannual variability, with little evidence for a trend towards more wintertime chemical depletion. However, increases in the burden of atmospheric halogens since the early 1970s are responsible for a large (14%) reduction in the average March column ozone, but this effect is mostly caused by increased destruction throughout the year rather than by halogen chemistry associated with wintertime polar statospheric clouds. Any influence of climate change on future average Arctic ozone amounts may thus be dominated by possible circulation changes, rather than by changes in chemical loss.

Chipperfield, M. P.; Jones, R. L.

1999-08-01

213

Microphysical Simulation of Polar Stratospheric Clouds Using WACCM/CARMA Model  

NASA Astrophysics Data System (ADS)

Polar stratospheric clouds (PSCs) form in the lower stratosphere during the polar night due to the cold temperature inside the polar vortex. PSCs are important to understand because they are responsible for the formation of the polar ozone hole each spring, including the unprecedented ozone depletion over the Arctic in spring 2011. We have studied the formation and evolution of liquid phase PSC particles (Super-cooled Ternary Solution, a.k.a. STS) in a microphysical model coupled with a 3D circulation model. Modeled STS particle volumes, size distributions, composition, coverage, and surface area density are compared to observations (CALIPSO, ACE, in-situ data, etc.) and chemistry model parameterization results.

zhu, Y.; Toon, O. B.

2011-12-01

214

Extreme ozone depletion in the 2010-2011 Arctic winter stratosphere as observed by MIPAS/ENVISAT using a 2-D tomographic approach  

NASA Astrophysics Data System (ADS)

We present observations of the 2010-2011 Arctic winter stratosphere from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard ENVISAT. Limb sounding infrared measurements were taken by MIPAS during the Northern polar winter and into the subsequent spring, giving a continuous vertically resolved view of the Arctic dynamics, chemistry and polar stratospheric clouds (PSCs). We adopted a 2-D tomographic retrieval approach to account for the strong horizontal inhomogeneity of the atmosphere present under vortex conditions, self-consistently comparing 2011 to the 2-D analysis of 2003-2010. Unlike most Arctic winters, 2011 was characterized by a strong stratospheric vortex lasting until early April. Lower stratospheric temperatures persistently remained below the threshold for PSC formation, extending the PSC season up to mid-March, resulting in significant chlorine activation leading to ozone destruction. On 3 January 2011, PSCs were detected up to 30.5 ± 0.9 km altitude, representing the highest PSCs ever reported in the Arctic. Through inspection of MIPAS spectra, 83% of PSCs were identified as supercooled ternary solution (STS) or STS mixed with nitric acid trihydrate (NAT), 17% formed mostly by NAT particles, and only two cases by ice. In the lower stratosphere at potential temperature 450 K, vortex average ozone showed a daily depletion rate reaching 100 ppbv day-1. In early April at 18 km altitude, 10% of vortex measurements displayed total depletion of ozone, and vortex average values dropped to 0.6 ppmv. This corresponds to a chemical loss from early winter greater than 80%. Ozone loss was accompanied by activation of ClO, associated depletion of its reservoir ClONO2, and significant denitrification, which further delayed the recovery of ozone in spring. Once the PSC season halted, ClO was reconverted primarily into ClONO2. Compared to MIPAS observed 2003-2010 Arctic average values, the 2010-2011 vortex in late winter had 15 K lower temperatures, 40% lower HNO3 and 50% lower ozone, reaching the largest ozone depletion ever observed in the Arctic. The overall picture of this Arctic winter was remarkably closer to conditions typically found in the Antarctic vortex than ever observed before.

Arnone, E.; Castelli, E.; Papandrea, E.; Carlotti, M.; Dinelli, B. M.

2012-10-01

215

A CCM simulation of the breakup of the Antarctic polar vortex in the years 1980-2004 under the CCMVal scenarios  

NASA Astrophysics Data System (ADS)

The changes in breakup time of the Antarctic polar vortex in the years 1980-2004 are examined using the output of chemistry climate model (CCM) calculations, data from the National Centers for Environmental Prediction/the National Center for Atmospheric Research (NCEP/NCAR) Reanalysis, and data from the European Center for Medium-Range Weather Forecasts Reanalysis (ERA40). The CCM used in this study is from the Center for Climate System Research/National Institute for Environmental Studies (CCSR/NIES). The CCM calculations are performed with the two ensemble members for REF1 scenario of the chemistry climate model validation (CCMVal) and the one ensemble member for the REF2 scenario. CCM simulates the development of the ozone hole from 1982 to 2000, as observed with a total ozone mapping spectrometer (TOMS), although the year-to-year variation is different from the observation owing to the internal variability of CCM and the ozone decreasing trends of CCM ozone in the two ensemble members of REF1 are underestimated. The trends in temperature and zonal mean zonal wind are analyzed and compared with the observations. There is consistency among the trends in zonal mean temperature, zonal mean zonal wind, and total ozone, but they differ among the ensemble members and observations. The diabatic heating rates and Eliassen-Palm flux fields are investigated in order to explain the differences. A delay trend in the breakup time of the Antarctic polar vortex is obtained for the period of 1980-1999 in the NCEP/NCAR and ERA40 data. A similar trend is also obtained from the CCM simulations, with statistical significance in one ensemble member of REF1 and REF2. Because the trends of the observations in the EP flux from the troposphere and its deposition in the lower stratosphere are consistent with an advanced breakup date of the polar vortex and because the trends of the CCM simulations are very small, it is likely that the Antarctic ozone depletion had some effect on the delay during the period 1980-1999. From 2000 to 2004, the NCEP/NCAR data show a large variation in breakup time, which makes the delay trend much less important. It is likely that the large variation in wave flux masked the effects of the ozone loss during that period. The two ensemble members of the REF1 simulation do not show such a dramatic change in the trend for the period 2000-2004, whereas REF2 shows a change in the trend for that period.

Akiyoshi, H.; Zhou, L. B.; Yamashita, Y.; Sakamoto, K.; Yoshiki, M.; Nagashima, T.; Takahashi, M.; Kurokawa, J.; Takigawa, M.; Imamura, T.

2009-02-01

216

Evidence for a QBO signature in polar summer mesopause temperatures over Antarctica  

NASA Astrophysics Data System (ADS)

We report on evidence for a QBO signature in southern polar summer mesopause temperatures that appears to be driven by the QBO signature in the northern polar vortex and transferred to the southern hemisphere via interhemispheric coupling. Measurements of polar stratospheric cloud (PSC) occurrence and chemical ozone losses in the Arctic polar vortex during the solar minimum period 2003 - 2009 with SCIAMACHY (Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY) on Envisat show a pronounced inter-annual variability consistent with the established QBO-signature during solar minimum conditions. Surprisingly, we find high and statistically significant correlations between monthly averaged PSC occurrence rates in February in the northern hemisphere and noctilucent cloud (NLC) occurrence rates in February in the southern hemisphere, indicating that a cold northern polar winter stratosphere corresponds to a cold southern polar summer mesopause. This finding can be interpreted as a consequence of the recently discovered and theoretically explained inter-hemispheric coupling mechanism, coupling the polar winter stratosphere with the polar summer mesopause through different stages of dynamical modification (Becker and Fritts, 2006). Given the known QBO-effect on the stability of the northern polar vortex during solar minimum conditions in combination with the established inter-hemispheric coupling suggests that the alternating averaged NLC occurrence rates at the southern polar summer mesospause are a QBO signature. The hypothesis is further tested using the 30 year SBUV data set of noctilucent clouds/polar mesospheric clouds (a proxy for polar summer mesopause temperatures).

von Savigny, C.; Bovensmann, H.; Burrows, J. P.; Deland, M. T.

2010-12-01

217

Microwave measurements of arctic chlorine monoxide and computed chemical ozone loss in spring 2000  

NASA Astrophysics Data System (ADS)

The University of Bremen (Germany) operates a microwave radiometer for the detection of stratospheric chlorine monoxide at 204 GHz, ozone at 142 GHz and water vapor at 22 GHz. The radiometer for atmospheric measurements (RAM) is located at the primary Arctic station of the Network for the Detection of Stratospheric Change - NDSC - in Ny-Ålesund, Spitsbergen at 79° North and 12° East. We observed a maximum chlorine monoxide (ClO) volume mixing ratio (VMR) of 1.2 ± 0.2 ppb in early March 2000 inside the polar vortex. The observed ClO decreased almost linearly to background values until late March. The vortex averaged chemical ozone loss derived from our observations accumulated to 45% at the 475 K isentropic level over the complete vortex existence period from December 1999 to March 2000.

Klein, U.; Lindner, K.; Bagdohn, S.; Wohltmann, I.; Künzi, K. F.

218

Interpretative synergy of starphotometry and lidar measurements at two high-Arctic stations during the Polar Winter of 2010-11  

NASA Astrophysics Data System (ADS)

Aerosols can significantly alter the Arctic's delicate radiative balance, both directly by absorbing and scattering solar and terrestrial radiation, and indirectly by influencing cloud properties through their critical role as cloud condensation nuclei. The understanding of aerosol dynamics, however, is especially poor in the Arctic, where our knowledge of the actual aerosol load, transport as well as physical and chemical properties is very limited. Among the biggest limitations is the absence of consistent night-time aerosol optical depth (AOD) measurements during the Polar Winter. AOD is a multi-spectral indicator of the total vertical extinction due to atmospheric aerosols and is one of the most important (aerosol) radiative forcing parameters. During the day, AOD is traditionally measured using the well-known sunphotometry technique, but night-time AOD measurements up to now have been extremely scarce. Recently developed starphotometry techniques based on extinction measurements of bright-star radiation help to mitigate the lack of any type consistent and regular Polar Night measurements. In an effort to address the dearth of AOD measurements during the Polar Winter , two starphotometers (denoted as SP-NYA and SP-PRL) were installed at two key high-Arctic stations: AWIPEV base at Ny Alesund (Spitsbergen, 78°55"N, 11°55"E) and the PEARL observatory at Eureka, Canada (79°59'N, 85°56'W). In the fall of 2010 both instruments were upgraded, in part to allow semi-automatic data acquisition with remote control capabilities. In addition to starphotometers, both stations are equipped with aerosol backscatter lidar systems: KARL (Koldeway Raman Lidar) and MPL (Micropulsed Lidar) at Ny Alesund and CRL (CANDAC Raman Lidar) at Eureka. During the 2010-11Polar Winter (Oct 2010-Mar 2011) measurements were performed whenever possible. We present preliminary event-driven results, for key optical parameters such as multi-band AOD, fine-mode (sub-micron) and coarse-mode (super-micron) optical depths that are derived from the star extinction measurements. We also show how the starphotometry-lidar synergy can be used in a routine analysis to better detect and characterize aerosol events. Finally, based on the preliminary evidence from satellite data and backward trajectories, we give some examples of potential aerosol transport into the Arctic during the Polar Winter.

Baibakov, K.; O'Neill, N. T.; Herber, A.; Ritter, C.; Duck, T. J.; Schulz, K.; Schrems, O.

2011-12-01

219

A study of ozone depletion in the 2004\\/2005 Arctic winter based on data from Odin\\/SMR and Aura\\/MLS  

Microsoft Academic Search

Ozone depletion in the colder than average 2004\\/2005 Arctic polar vortex is mapped and quantified using ozone profiles from two limb sounding satellite instruments, the Earth Observing System Microwave Limb Sounder (Aura\\/MLS) and the Odin Sub-Millimetre Radiometer (Odin\\/SMR). Profiles of chemically inert nitrous oxide (N2O) are used to trace vertical transport during the winter. Two methods are used for estimating

J. D. Rösevall; D. P. Murtagh; J. Urban; W. Feng; P. Eriksson; S. Brohede

2008-01-01

220

Short period gravity waves in the Arctic atmosphere over Alaska  

NASA Astrophysics Data System (ADS)

The propagation nature and sources of short-period gravity waves have been studied extensively at low and mid-latitudes, while their extent and nature at the polar regions are less known. During the last decade, observations from select sites on the Antarctic continent have revealed a significant presence of these waves over the southern Polar Region as well as shown unexpected dynamical behavior. In contrast, observations over the Arctic region are few and the dynamical behavior is unknown. A recent project was initiated in January 2011 to investigate the presence and dynamics of these waves over interior Alaska. This site provides an exceptional opportunity to establish a long-term climatology of short-period gravity waves in the Arctic, including their dominant source regions, influences of large-scale tidal and planetary wave motion, as well as impact of dominant weather systems such as the polar vortex and Aleutian low. Here we present initial measurements of short-period gravity waves in the Arctic atmosphere over Alaska.

Negale, Michael; Nielsen, Kim; Taylor, Mike; Irving, Brita; Collins, Richard

2012-10-01

221

Arctic Melting  

NSDL National Science Digital Library

In this radio broadcast, a panel of experts joins National Public Radio journalist Diane Rehm to discuss rising temperatures at the North Pole and what the melting may mean for the climate, national boundaries, and oil exploration. There is discussion of the 1982 U.N. convention, Law of the Sea, which is guiding new mapping due to arctic melting and changing coastlines; and why the decreasing need for Arctic ice-breakers is making oil exploration mapping easier. There is explanation of why the Antarctic may melt a couple of decades after the Arctic; why we know sea levels will rise as polar ice melts; and why we know humans are causing the melting, as opposed to astronomical configurations or other natural causes leading to melting cycles. The broadcast is 51 minutes in length, but the discussion about the Arctic starts 32 minutes into the program and lasts 19 minutes. You may listen to the archived broadcast in Windows Media or Real Audio format.

2011-06-15

222

Organic and inorganic bromine compounds and their composition in the Arctic troposphere during polar sunrise  

SciTech Connect

Particle and gas phase inorganic bromine, total organic bromine, and several individual organic bromine species were measured in the troposphere during the Polar Sunrise Experiment at Alert, Northwest Territories, Canada, during January 18 to April 21, 1992. The measurements revealed the following: (1) Particle bromide increased gradually from about 10 ng(Br)/m{sup 3} during the dark period to >20 ng(Br)/m{sup 3} during the light period, with a marked peak of 120 ng(Br)/m{sup 3} corresponding to a strong O{sub 3} depletion event. (2) Inorganic gaseous bromine (InorgBr) was about 60 ng(Br)/m{sup 3} during the dark period and relatively constant. A major peak, up to 280 ng(Br)/m{sup 3}, before sunrise accompanied a similar peak in the total organic bromine. After sunrise the peaks in InorgBr corresponded to O{sub 3} depletion periods. InorgBr appeared to be the sum of HBr, HOBr, and Br{sub 2}. (3) Total organic bromine was relatively constant before sunrise at 100 ng(Br)/m{sup 3} but more variable afterward, up to 280 ng(Br)/m{sup 3}. Individual species include CHBr{sub 3} with levels of 7-60 ng(Br)/m{sup 3}. CH{sub 2}Br{sub 2}, CH{sub 2}ClBr, CHClBr{sub 2}, and CHCl{sub 2}Br levels were lower at 0.5-7.5 ng(Br)/m{sup 3}. CHBr{sub 3} was the largest contributor to total organic bromine of the five species, on average accounting for 23%, while the other four species amounted to less than 5% on average. (4) CHBr{sub 3}, CHClBr{sub 2} and CHCl{sub 2}Br were significantly correlated. The ratio CHClBr{sub 2}/CHBr{sub 3} decreased linearly with increasing ln(CHBr{sub 3}), with a steeper decrease after sunrise than before. The decreases suggest different rates of destruction with CHBr{sub 3} having a larger rate constant than CHClBR{sub 2}. A similar relationship existed between the ratio CHCl{sub 2}Br/CHClBr{sub 2}, but the dark period slope was near zero, indicating a greater difference in rates in the two species in the light period. 37 refs., 9 figs., 3 tabs.

Li, S.M.; Barrie, L.A.; Bottenheim, J.W. [Atmospheric Environment Service, Ontario (Canada)] [and others

1994-12-20

223

Radio Frequency Identification Tags for Grizzly and Polar Bear Research, Technical Summary.  

National Technical Information Service (NTIS)

Grizzly and polar bears are important species for subsistence communities along the Arctic coast and they are important components of arctic terrestrial, nearshore and, in the case of polar bears, arctic marine ecosystems. Polar bears were listed as threa...

L. T. Quakenbush

2009-01-01

224

Polar stratospheric ozone: interactions with climate change, results from the EU project RECONCILE, and the 2010/11 Arctic ozone hole  

NASA Astrophysics Data System (ADS)

One of the most profound and well known examples of human impacts on atmospheric chemistry is the so called ozone hole. During the second half of the 20th century, anthropogenic emissions of chlorofluorocarbons (CFCs) led to a significant increase in stratospheric chlorine levels and hence the rate of ozone removal by catalytic cycles involving chlorine. While CFCs were essentially banned by the 1987 Montreal Protocol and its subsequent amendments, and stratospheric chlorine levels have recently started to decline again, another anthropogenic influence may at least delay the recovery of the stratospheric ozone layer: climate change, with little doubt a result of human emissions of carbon dioxide and other greenhouse gases, has led to changes in stratospheric temperature and circulation. The large ozone losses that typically occur in polar regions in spring are particularly affected by these changes. Here, we give an overview of the ozone-climate interactions affecting polar stratospheric ozone loss, and present latest results from the international research project RECONCILE funded by the European Commission. Remaining open questions will be discussed including the possible impacts of recently suggested geoengineering concepts to artificially enhance the stratospheric aerosol loading. A special focus will also be put on the 2010/11 Arctic winter that saw the first Arctic Ozone hole, including an impact study on surface UV radiation in the densely populated northern mid-latitudes.

von Hobe, Marc

2013-04-01

225

Effects of environmental variation and spatial distance on Bacteria, Archaea and viruses in sub-polar and arctic waters  

PubMed Central

We investigated the influence of environmental parameters and spatial distance on bacterial, archaeal and viral community composition from 13 sites along a 3200-km long voyage from Halifax to Kugluktuk (Canada) through the Labrador Sea, Baffin Bay and the Arctic Archipelago. Variation partitioning was used to disentangle the effects of environmental parameters, spatial distance and spatially correlated environmental parameters on prokaryotic and viral communities. Viral and prokaryotic community composition were related in the Labrador Sea, but were independent of each other in Baffin Bay and the Arctic Archipelago. In oceans, the dominant dispersal mechanism for prokaryotes and viruses is the movement of water masses, thus, dispersal for both groups is passive and similar. Nevertheless, spatial distance explained 7–19% of the variation in viral community composition in the Arctic Archipelago, but was not a significant predictor of bacterial or archaeal community composition in either sampling area, suggesting a decoupling of the processes regulating community composition within these taxonomic groups. According to the metacommunity theory, patterns in bacterial and archaeal community composition suggest a role for species sorting, while patterns of virus community composition are consistent with species sorting in the Labrador Sea and suggest a potential role of mass effects in the Arctic Archipelago. Given that, a specific prokaryotic taxon may be infected by multiple viruses with high reproductive potential, our results suggest that viral community composition was subject to a high turnover relative to prokaryotic community composition in the Arctic Archipelago.

Winter, Christian; Matthews, Blake; Suttle, Curtis A

2013-01-01

226

Moisture transport and Atmospheric circulation in the Arctic  

NASA Astrophysics Data System (ADS)

Cyclones are an important feature of the Mid-Latitudes and Arctic Climates. They are a main transporter of warm moist energy from the sub tropics to the poles. The Arctic Winter is dominated by highly stable conditions for most of the season due to a low level temperature inversion caused by a radiation deficit at the surface. This temperature inversion is a ubiquitous feature of the Arctic Winter Climate and can persist for up to weeks at a time. The inversion can be destroyed during the passage of a cyclone advecting moisture and warming the surface. In the absence of an inversion, and in the presence of this warm moist air mass, clouds can form quite readily and as such influence the radiative processes and energy budget of the Arctic. Wind stress caused by a passing cyclones also has the tendency to cause break-up of the ice sheet by induced rotation, deformation and divergence at the surface. For these reasons, we wish to understand the mechanisms of warm moisture advection into the Arctic from lower latitudes and how these mechanisms are controlled. The body of work in this area has been growing and gaining momentum in recent years (Stramler et al. 2011; Morrison et al. 2012; Screen et al. 2011). However, there has been no in depth analysis of the underlying dynamics to date. Improving our understanding of Arctic dynamics becomes increasingly important in the context of climate change. Many models agree that a northward shift of the storm track is likely in the future, which could have large impacts in the Arctic, particularly the sea ice. A climatology of six-day forward and backward trajectories starting from multiple heights around 70 N is constructed using the 22 year ECMWF reanalysis dataset (ERA-INT). The data is 6 hourly with a horizontal resolution of 1 degree on 16 pressure levels. Our methodology here is inspired by previous studies examining flow patterns through cyclones in the mid-latitudes. We apply these earlier mid-latitude methods in the Arctic. We investigate an Arctic trajectory dataset and provide a phenomenological/descriptive analysis of these trajectories, including key meteorological variables carried along trajectories. The trajectory climatology is linked to a previously established cyclone climatology dataset from Hanley and Caballero (2011). We associate trajectories and the meteorological variables they are carrying to cyclones in this dataset. A climatology of 'Arctic-influencing' cyclones is constructed from the cyclone dataset. The resilience of the polar vortex and its effect on circulation, via blocking and breaking, is examined in relation to our trajectory climatology.

Woods, Cian; Caballero, Rodrigo

2013-04-01

227

Effect of Polar Day on Plasma Profiles of Melatonin, Testosterone, and Estradiol in High-Arctic Lapland Longspurs  

Microsoft Academic Search

In polar habitats, continuous daylight (polar day) can prevail for many weeks or months around the summer solstice. In the laboratory, continuous light conditions impair or disrupt circadian rhythms in many animals. To determine whether circadian rhythms are disrupted under natural polar day conditions in a species that is only a summer resident in polar regions we analyzed diel rhythms

Michaela Hau; L. Michael Romero; Jeff D. Brawn; Thomas J. Van't Hof

2002-01-01

228

In situ measurements of the ClO\\/HCl ratio: Heterogeneous processing on sulfate aerosols and polar stratospheric clouds  

Microsoft Academic Search

Simultaneous in situ measurements of stratospheric ClO and HCl have been made for the first time, during numerous flights of the ER-2 aircraft covering latitudes 24-90[degrees]N from October 1991 through March 1992. The ClO\\/HCl ratio is identified as a key indicator of heterogeneous processing both outside and within the Arctic polar vortex. For ClO mixing ratios below about 120 pptv,

C. R. Webster; R. D. May; D. W. Toohey; L. M. Avallone; J. G. Anderson; S. Solomon

1993-01-01

229

Extensive sampling of polar bears (Ursus maritimus) in the Northwest Passage (Canadian Arctic Archipelago) reveals population differentiation across multiple spatial and temporal scales  

PubMed Central

As global warming accelerates the melting of Arctic sea ice, polar bears (Ursus maritimus) must adapt to a rapidly changing landscape. This process will necessarily alter the species distribution together with population dynamics and structure. Detailed knowledge of these changes is crucial to delineating conservation priorities. Here, we sampled 361 polar bears from across the center of the Canadian Arctic Archipelago spanning the Gulf of Boothia (GB) and M'Clintock Channel (MC). We use DNA microsatellites and mitochondrial control region sequences to quantify genetic differentiation, estimate gene flow, and infer population history. Two populations, roughly coincident with GB and MC, are significantly differentiated at both nuclear (FST = 0.01) and mitochondrial (?ST = 0.47; FST = 0.29) loci, allowing Bayesian clustering analyses to assign individuals to either group. Our data imply that the causes of the mitochondrial and nuclear genetic patterns differ. Analysis of mtDNA reveals the matrilineal structure dates at least to the Holocene, and is common to individuals throughout the species’ range. These mtDNA differences probably reflect both genetic drift and historical colonization dynamics. In contrast, the differentiation inferred from microsatellites is only on the scale of hundreds of years, possibly reflecting contemporary impediments to gene flow. Taken together, our data suggest that gene flow is insufficient to homogenize the GB and MC populations and support the designation of GB and MC as separate polar bear conservation units. Our study also provide a striking example of how nuclear DNA and mtDNA capture different aspects of a species demographic history.

Campagna, Leonardo; Van Coeverden de Groot, Peter J; Saunders, Brenda L; Atkinson, Stephen N; Weber, Diana S; Dyck, Markus G; Boag, Peter T; Lougheed, Stephen C

2013-01-01

230

Extensive sampling of polar bears (Ursus maritimus) in the Northwest Passage (Canadian Arctic Archipelago) reveals population differentiation across multiple spatial and temporal scales.  

PubMed

As global warming accelerates the melting of Arctic sea ice, polar bears (Ursus maritimus) must adapt to a rapidly changing landscape. This process will necessarily alter the species distribution together with population dynamics and structure. Detailed knowledge of these changes is crucial to delineating conservation priorities. Here, we sampled 361 polar bears from across the center of the Canadian Arctic Archipelago spanning the Gulf of Boothia (GB) and M'Clintock Channel (MC). We use DNA microsatellites and mitochondrial control region sequences to quantify genetic differentiation, estimate gene flow, and infer population history. Two populations, roughly coincident with GB and MC, are significantly differentiated at both nuclear (F ST = 0.01) and mitochondrial (?ST = 0.47; F ST = 0.29) loci, allowing Bayesian clustering analyses to assign individuals to either group. Our data imply that the causes of the mitochondrial and nuclear genetic patterns differ. Analysis of mtDNA reveals the matrilineal structure dates at least to the Holocene, and is common to individuals throughout the species' range. These mtDNA differences probably reflect both genetic drift and historical colonization dynamics. In contrast, the differentiation inferred from microsatellites is only on the scale of hundreds of years, possibly reflecting contemporary impediments to gene flow. Taken together, our data suggest that gene flow is insufficient to homogenize the GB and MC populations and support the designation of GB and MC as separate polar bear conservation units. Our study also provide a striking example of how nuclear DNA and mtDNA capture different aspects of a species demographic history. PMID:24102001

Campagna, Leonardo; Van Coeverden de Groot, Peter J; Saunders, Brenda L; Atkinson, Stephen N; Weber, Diana S; Dyck, Markus G; Boag, Peter T; Lougheed, Stephen C

2013-08-03

231

Life in a temperate Polar sea: a unique taphonomic window on the structure of a Late Cretaceous Arctic marine ecosystem  

PubMed Central

As the earth faces a warming climate, the rock record reminds us that comparable climatic scenarios have occurred before. In the Late Cretaceous, Arctic marine organisms were not subject to frigid temperatures but still contended with seasonal extremes in photoperiod. Here, we describe an unusual fossil assemblage from Devon Island, Arctic Canada, that offers a snapshot of a ca 75?Myr ago marine palaeoecosystem adapted to such conditions. Thick siliceous biogenic sediments and glaucony sands reveal remarkably persistent high primary productivity along a high-latitude Late Cretaceous coastline. Abundant fossil faeces demonstrate that this planktonic bounty supported benthic invertebrates and large, possibly seasonal, vertebrates in short food chains. These ancient organisms filled trophic roles comparable to those of extant Arctic species, but there were fundamental differences in resource dynamics. Whereas most of the modern Arctic is oligotrophic and structured by resources from melting sea ice, we suggest that forested terrestrial landscapes helped support the ancient marine community through high levels of terrigenous organic input.

Chin, Karen; Bloch, John; Sweet, Arthur; Tweet, Justin; Eberle, Jaelyn; Cumbaa, Stephen; Witkowski, Jakub; Harwood, David

2008-01-01

232

A study of the vertical scale of halogen chemistry in the Arctic troposphere during Polar Sunrise at Barrow, Alaska  

Microsoft Academic Search

The vertical extent and impact of halogen chemistry in the Arctic springtime was investigated through balloon-based measurement of several atmospheric chemical components. Various chemical species, including volatile organic compounds (VOCs), ozone, and elemental mercury, that are modified by halogen chemistry were measured from the surface to ?300 m during late March through mid-April 2005 in Barrow, Alaska. It is observed

Philip J. Tackett; Aubrey E. Cavender; Adam D. Keil; Paul B. Shepson; Jan W. Bottenheim; Samuel Morin; John Deary; Alexandra Steffen; Chris Doerge

2007-01-01

233

Polar vortex dynamics during spring and fall diagnosed using trace gas observations from the Atmospheric Trace Molecule Spectroscopy instrument  

Microsoft Academic Search

Trace gases measured by the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument during three Atmospheric Laboratory for Applications and Science (ATLAS) space-shuttle missions, in March\\/April 1992 (AT-1), April 1993 (AT-2), and November 1994 (AT-3) have been mapped into equivalent latitude\\/potential temperature (EqL\\/theta) coordinates. The asymmetry of the spring vortices results in coverage of subtropical to polar EqLs. EqL\\/theta fields of long-lived

G. L. Manney; H. A. Michelsen; M. L. Santee; M. R. Gunson; F. W. Irion; A. E. Roche; N. J. Livesey

1999-01-01

234

Rayleigh Lidar Network Observations and Analysis of the Evolution of the Arctic Middle Atmosphere during the IPY Winter 2007-2008  

NASA Astrophysics Data System (ADS)

A network of five Rayleigh lidars (i.e., Kuehlungsborn, Germany (54N, 12E), Chatanika, USA (65N, 147W), Kangerlussuaq, Greenland (67N, 51W), Andoya, Norway (69N, 16E), and Eureka, Canada (80N, 86W)) has been used to measure middle atmosphere temperature profiles through the 2007-2008 winter and spring. These measurements are being made as part of the project Pan-Arctic Studies of the Coupled Tropospheric, Stratospheric and Mesospheric Circulation as part of the Fourth International Polar Year (IPY-4). This project is a component of the two full IPY proposals; International Arctic Systems for Observing the Atmosphere (IASOA) and The Structure and Evolution of the Polar Stratosphere and Mesosphere and Links to the Troposphere during IPY (SPARC-IPY). The lidar network is part of the Arctic Observing Network (AON). The resolution and distribution of these lidar measurements provides the basis for a pan-Arctic perspective of the middle atmosphere circulation. We combine these lidar data with satellite observations and meteorological re-analyses to study the structure, evolution, and variability of the Arctic stratospheric vortex and Aleutian anticyclone. In this study we present the evolution of the Arctic middle atmosphere during the winter of 2007-2008. We highlight a stratospheric warming event that occurred during 20-26 February 2008. During this week the vortex was disrupted by the Aleutian anticyclone, then split at higher altitudes, and eventually reformed. The lidar measurements show that the altitude and temperature of the stratopause vary considerably (10 km, 30 K) from night-to-night and that the observed temperature structure often differs from that reported by the standard climatologies (e.g., SPARC). We discuss the observations in terms of the Study of Environmental Arctic Change (SEARCH).

Collins, R. L.; Harvey, V. L.; Thurairajah, B.; Atkinson, D. E.; Larsen, C. J.; Baumgarten, G.; Fiedler, J.; Firanski, B. J.; Gerding, M.; Hoeffner, J.; Livingston, J. M.; Luebken, F.; Mizutani, K.; Pan, W.; Sica, R. J.; Strawbridge, K. B.

2008-12-01

235

Hematology of Southern Beaufort Sea Polar Bears (2005–2007): Biomarker for an Arctic Ecosystem Health Sentinel  

Microsoft Academic Search

Declines in sea-ice habitats have resulted in declining stature, productivity, and survival of polar bears in some regions.\\u000a With continuing sea-ice declines, negative population effects are projected to expand throughout the polar bear’s range. Precise\\u000a causes of diminished polar bear life history performance are unknown, however, climate and sea-ice condition change are expected\\u000a to adversely impact polar bear (Ursus maritimus)

Cassandra M. Kirk; Steven Amstrup; Rhonda Swor; Darce Holcomb; Todd M. O’Hara

2010-01-01

236

Ozone profile distributions in the Arctic from GOME satellite observations during spring 1997 and 1998  

NASA Astrophysics Data System (ADS)

The Global Ozone Monitoring Experiment (GOME) aboard ESA's ERS-2 satellite measures the reflected and backscattered radiation from the Earth in the UV/visible spectral range at moderate spectral resolution. Vertical ozone profile distributions can be derived form top-of-atmosphere nadir observations using the Full Retrieval Method FURM, which is based upon an advanced Optimal Estimation inversion scheme. During the Arctic spring seasons 1997 and 1998 hemispheric ozone profile distributions have been derived from GOME observations. In 1997 the polar vortex formed late in winter and record low temperatures were reached in late March. In the lower stratosphere depleted levels of ozone were observed by GOME. From vertical ozone distributions inside the polar vortex obtained on 24 days between 9 March and 16 May 1997, chemical ozone loss rates in the lower stratosphere are estimated. The lower stratospheric temperatures in spring 1998 were comparable to the longterm mean and the polar vortex was relatively weak. Preliminary results from this period are also presented. In both spring seasons ozone mini-hole events, which are characterized by intrusion of ozone poor subtropical air into mid and polar latitudes, were observed. From transects of GOME orbits the 2D structure of the zone mini-hole can be studied in detail.

Eichmann, Kai-Uwe; Weber, M.; Bramstedt, K.; Hoogen, R.; Rozanov, Vladimir; Burrows, John P.

1998-12-01

237

In situ observations of ClO in the Arctic stratosphere: ER-2 aircraft results from 59 degree N to 80 degree N latitude  

SciTech Connect

Large abundances of ClO were observed inside the Arctic polar vortex during 14 flights of the NASA ER-2 aircraft from Stavanger, Norway (59{degree}N, 6{degree}E) to 80{degree}N latitude. Flights were conducted at altitudes between 14 and 20 km when the solar zenith angle was between 70{degree} and 101{degree}. Data are reported for three flights, January 6, January 16, and February 10, that represent the main features observed during the mission. ClO mixing ratios were typically less than 50 parts per trillion by volume (pptv) outside the vortex and exceeded 100 pptv inside the vortex for all flights. ClO mixing ratios were more than 500 pptv for four days in a row in early February, reaching 1,130 pptv on February 10, at an altitude of 19 km (potential temperature of 460 K). Peak ClO mixing ratios in early February were {approximately}100 times larger than those observed at mid-latitudes for all altitudes surveyed between 15 and 19 km. These data, comparable to those obtained in the Antarctic ozone hole, indicate that the springtime Arctic polar vortex was extensively perturbed by heterogeneous chemistry and contained enough ClO to catalytically destroy ozone rapidly.

Brune, W.H. (Pennsylvania State Univ., University Park (USA)); Toohey, D.W.; Anderson, J.G. (Harvard Univ., Cambridge, MA (USA)); Chan, K.R. (NASA Ames Research Center, Moffett Field, CA (USA))

1990-03-01

238

Contamination of food by crude oil affects food selection and growth performance, but not appetite, in an Arctic fish the polar cod (Boreogadus saida)  

SciTech Connect

The polar cod (Boreogadus saida) is recognized as a key species in Arctic marine food webs and it may, therefore, be important for the transfer of xenobiotics from lower trophic levels to its main predators, birds and sea mammals. The present work examines the effects of foods contaminated with 200 or 400 ppm crude oil on food selection patterns and appetite-growth relationship in polar cod using X-radiography. It is shown that sexually mature polar cod consumed mixtures of uncontaminated and oil-contaminated foods, and did not show a reduced overall appetite as compared with fish provided with uncontaminated food only. Food selection was, however, influenced by both sex and individual appetite. Male fish selected uncontaminated food when appetite was low, whereas females ingested contaminated and uncontaminated foods equally, irrespective of appetite level. The ingestion of oil-contaminated food led to a significant depression in growth performance in both male and female fish. Food contaminated with oil at a concentration of 500 ppm was completely rejected by both sexes. 6 refs., 4 figs., 2 tabs.

Christiansen, J.S. [Norwegian Institute of Fisheries and Aquaculture, Troms (Norway); George, S.G. [Univ. of Stirling, Scotland (United Kingdom)

1995-04-01

239

International Polar Year GEOTRACES: an International Study of the Biogeochemical Cycles of Trace Elements and Isotopes in the Arctic and Southern Oceans  

NASA Astrophysics Data System (ADS)

Trace elements and their isotopes play an important role in oceanography as participants in, and as tracers of, processes of fundamental interest. Some trace elements (e.g., Fe, Co, Zn) serve as essential micronutrients, the availability of which influences the physiological state and biochemical activity of marine organisms. This, in turn, controls the structure of ocean ecosystems and their biological productivity. For example, Fe is the key limiting trace nutrient in the Southern Ocean. Moreover several natural stable and radio- isotopes in the oceans serve as tracers of specific ocean processes like mixing, biogenic export, or adsorption. Quantification of such processes is feasible via mass fractionation or decay rate of the selected isotope. In context of worldwide GEOTRACES, scientists of 19 nations are developing an intensive observation program during the International Polar Year to detect and understand a suite of trace elements and isotopes in the Arctic and Antarctic marine environment.

de Baar, H. J.; Anderson, R.

2006-12-01

240

Odd-Hydrogen Photochemistry and Inferring Water Vapor in the Arctic Summer Mesosphere: Implications for Polar Mesospheric Clouds  

Microsoft Academic Search

We will present results of an investigation of odd-hydrogen (HOx = H + OH + HO2) and odd-oxygen (Ox = O + O3) photochemistry in the Arctic mesosphere. In these studies we utilize a one-dimensional photochemical model of Ox\\/HOx species to compare with high latitude observations of OH and O3 from the August, 1997 flight of the CRISTA (Cryogenic Infrared

M. E. Summers; C. R. Englert; D. E. Siskind; M. H. Stevens

2001-01-01

241

Simultaneous Traveling Convection Vortex (TCV) Events and Pc 1-2 Wave Bursts at Cusp/Cleft Latitudes observed in Arctic Canada and Svalbard  

NASA Astrophysics Data System (ADS)

Traveling convection vortices (TCVs), which appear in ground magnetometer records at near-cusp latitudes as solitary ~5 mHz pulses, are now known to originate in instabilities in the ion foreshock just upstream of Earth’s bow shock. They can also stimulate compressions or relaxations of the dayside magnetosphere (evident in geosynchronous satellite data). These transient compressions can in turn sharply increase the growth rate of electromagnetic ion cyclotron (EMIC) waves, which also appear in ground records at near-cusp latitudes as bursts of Pc 1-2 pulsations. In this study we have identified simultaneous TCV - Pc 1-2 burst events occurring from 2008 through the first 7 months of 2010 in Eastern Arctic Canada and Svalbard, using a combination of fluxgate magnetometers (MACCS and IMAGE) and search coil magnetometers in each region. Magnetometer observations at GOES 10 and 12, at longitudes near the MACCS sites, are also used to characterize the strength of the magnetic perturbations. There is no direct proportion between the amplitude of TCV and Pc 1-2 wave events in either region, consistent with the highly variable densities and pitch angle distributions of plasma of ring current / plasma sheet energies in the outer dayside magnetosphere.

Posch, J. L.; Witte, A. J.; Engebretson, M. J.; Murr, D.; Lessard, M.; Raita, T.; Singer, H. J.

2010-12-01

242

Arctic ozone depletion in 2002-2003 measured by ASUR and comparison with POAM observations  

NASA Astrophysics Data System (ADS)

We present ozone loss estimated from airborne measurements taken during January-February and March in the Arctic winter 2002/2003. The first half of the winter was characterized by unusually cold temperatures and the second half by a major stratospheric sudden warming around 15-18 January 2003. The potential vorticity maps show a vortex split in the lower stratosphere during the major warming (MW) in late January and during the minor warming in mid-February due to wave 1 amplification. However, the warming can be termed as a vortex displacement event as there was no vortex split during the MW period at 10 hPa. Very low temperatures, large areas of polar stratospheric clouds (PSCs), and high chlorine activation triggered significant ozone loss in the early winter, as the vortex moved to the midlatitude regions. The ozone depletion derived from the ASUR measurements sampled inside the vortex, in conjunction with the Mimosa-Chim model tracer, shows a maximum of 1.3 ± 0.2 ppmv at 450-500 K by late March. The partial column loss derived from the ASUR ozone profiles reaches up to 61 ± 4 DU in 400-550 K in the same period. The evolution of ozone and ozone loss assessed from the ASUR measurements is in very good agreement with POAM observations. The reduction in ozone estimated from the POAM measurements shows a similar maximum of 1.3 ± 0.2 ppmv at 400-500 K or 63 ± 4 DU in 400-550 K in late March. Our study reveals that the Arctic winter 2002/2003 was unique as it had three minor warmings and a MW, yet showed large loss in ozone. No such feature was observed in any other Arctic winter in the 1989-2010 period. In addition, an unusually large ozone loss in December, around 0.5 ± 0.2 ppmv at 450-500 K or 12 ± 1 DU in 400-550 K, was estimated for the first time in the Arctic. A careful and detailed diagnosis with all available published results for this winter exhibits an average ozone loss of 1.5 ± 0.3 ppmv at 450-500 K or 65 ± 5 DU in 400-550 K by the end of March, which exactly matches the ozone depletion derived from the ASUR, POAM and model data. The early ozone loss together with considerable loss afterwards put the warm Arctic winter 2002/2003 amongst the moderately cold winters in terms of the significance of the ozone loss.

Kuttippurath, Jayanarayanan; KleinböHl, Armin; Sinnhuber, Miriam; Bremer, Holger; Küllmann, Harry; Notholt, Justus; Godin-Beekmann, Sophie; Tripathi, Omprakash; Nikulin, Grigory

2011-11-01

243

Regular and chaotic vortex core reversal by a resonant perpendicular magnetic field  

NASA Astrophysics Data System (ADS)

Under the action of an alternating perpendicular magnetic field, the polarity of the vortex state nanodisk can be efficiently switched. We predict the regular and chaotic dynamics of the vortex polarity and propose a simple analytical description in terms of a reduced vortex core model. Conditions for the controllable polarity switching are analyzed.

Pylypovskyi, Oleksandr V.; Sheka, Denis D.; Kravchuk, Volodymyr P.; Mertens, Franz G.; Gaididei, Yuri

2013-07-01

244

From polar night to midnight sun: photoperiod, seal predation, and the diel vertical migrations of polar cod ( Boreogadus saida ) under landfast ice in the Arctic Ocean  

Microsoft Academic Search

The winter\\/spring vertical distributions of polar cod, copepods, and ringed seal were monitored at a 230-m station in ice-covered\\u000a Franklin Bay. In daytime, polar cod of all sizes (7–95 g) formed a dense aggregation in the deep inverse thermocline (160–230 m,\\u000a ?1.0 to 0°C). From December (polar night) to April (18-h daylight), small polar cod <25 g migrated into the isothermal cold\\u000a intermediate

Delphine Benoit; Yvan Simard; Jacques Gagné; Maxime Geoffroy; Louis Fortier

2010-01-01

245

The influence of polar heterogeneous processes on reactive chlorine at middle latitudes: Three dimensional model implications  

SciTech Connect

Three dimensional model calculations with the NASA/GSFC chemistry and transport model have been designed to consider the impact of heterogeneous processes occurring on polar stratospheric clouds (PSC's) in the Arctic vortex on the HCl distribution. By examining the HCl concentration for a calculation with PSC's relative to a calculation with gas phase chemistry only, the authors infer the impact of polar processing on reactive chlorine species at middle latitudes. Results from the chemistry and transport model reproduce basic features of the ClO measurements (Toohey et al., 1991), which were made on the ferry flights of the ER-2 from Stavanger, Norway to Moffett Field, California via Wallops Island, Virginia on February 20 and 21, 1989. The model indicates that perturbed air which is contained within the polar vortex during winter is not homogeneously mixed, and that the ferry flights were made through air with the largest conversion of HCl to reactive chlorine that is seen at middle latitudes.

Douglass, A.R.; Rood, R.B.; Kaye, J.A.; Stolarski, R.S. (NASA/Goddard Space Flight Center, Greenbelt, MD (USA)); Allen, D.J.; Larson, E.M.

1991-01-01

246

The influence of polar heterogeneous processes on reactive chlorine at middle latitudes - Three dimensional model implications  

NASA Astrophysics Data System (ADS)

Three-dimensional model calculations with the NASA/GSFC chemistry and transport model have been designed to consider the impact of heterogeneous processes occurring on polar stratospheric clouds (PSCs) in the Arctic vortex on the HCl distribution. By examining the HCl concentration for a calculation with PSCs relative to a calculation with gas phase chemistry only, the impact of polar processing on reactive chlorine species at middle latitudes is inferred. Results from the chemistry and transport model reproduce basic features of the ClO measurements (Toohey et al., 1991), which were made on the ferry flights of the ER-2 from Stavanger, Norway to Moffett Field, California via Wallops Island, Virginia on February 20 and 21, 1989. The model indicates that perturbed air which is contained within the polar vortex during winter is not homogeneously mixed, and that the ferry flights were made through air with the largest conversion of HCl to reactive chlorine that is seen at middle latitudes.

Douglass, Anne R.; Rood, Richard B.; Kaye, Jack A.; Stolarki, Richard S.; Allen, Dale J.

1991-01-01

247

Teachers, Researchers, and Students Collaborating in Arctic Climate Change Research: The Partnership Between the Svalbard REU and ARCUS PolarTREC programs  

NASA Astrophysics Data System (ADS)

Since 2004, the Arctic Research Consortium of the U.S. (ARCUS) "TREC" program (Teachers and Researchers Exploring and Collaborating, now "PolarTREC") has sent four K-12 teachers to Svalbard, Norway to work alongside researchers and undergraduate students conducting climate change research as part of the Svalbard Research Experiences for Undergraduates (REU) Program. The benefits of this scientist/educator/student partnership are many. Researchers benefit from teacher participation as it increases their understanding of student learning and the roles and responsibilities of K-12 teachers. The TREC teacher contributes to the research by making observations, analyzing data, and carrying heavy loads of equipment. In collaborating with K- 12 teachers, undergraduate student participants discover the importance of teamwork in science and the need for effective communication of scientific results to a broad audience. The questions that K-12 teachers ask require the scientists and students in our program to explain their work in terms that non-specialists can understand and appreciate. The K-12 teacher provides a positive career role model and several Svalbard REU undergraduate students have pursued K-12 teaching careers after graduating. TREC teachers benefit from working alongside the researchers and by experiencing the adventures of real scientific research in a remote arctic environment. They return to their schools with a heightened status that allows them to share the excitement and importance of scientific research with their students. Together, all parties contribute to greatly enhance public outreach. With ARCUS logistical support, TREC teachers and researchers do live web conferences from the field, reaching hundreds of students and dozens of school administrators and even local politicians. Teachers maintain web journals, describing the daily activities and progress of the researcher team. Online readers from around the world write in to ask questions, which the TREC teacher answers after consulting the research team. TREC teachers have developed and distributed teaching modules using real questions and data from the research program. Our collaboration is successful in part because the teachers are well prepared by ARCUS in advance of the field experience and the Svalbard REU leaders treat the TREC teacher as a senior member of the research team. Reliable telephone and internet communication from the field site is also important because it greatly facilitates the daily outreach. Our success is measured by the hundreds of K-12 students exposed to arctic climate change research (some of which are now going to college to pursue geoscience studies!) and the mutual desire for continued collaboration between the Svalbard REU Program and the ARCUS PolarTREC Program.

Roof, S.; Warburton, J.; Oddo, B.; Kane, M.

2007-12-01

248

Conservation Plan for the Polar Bear in Alaska.  

National Technical Information Service (NTIS)

Polar bears (Ursus maritimus) are a species unique to the Arctic. Polar bears have coexisted through time with indigenous peoples of the Arctic. Polar bears are long-lived, latematuring carnivores that have relatively low rates of reproduction and natural...

1994-01-01

249

Vortex methods.  

National Technical Information Service (NTIS)

Vortex methods originated from the observation that in incompressible inviscid flow vorticity (or, more accurately, circulation) is a conserved quantity, as can be readily deduced from the absence of tangential stresses. Thus, if the vorticity is known at...

A. J. Chorin

1993-01-01

250

Vortex Bursting.  

National Technical Information Service (NTIS)

Vortex bursting is studied by means of visualization. The physical behavior of the phenomenon is emphasized, and its similarity with boundary layer separation or wake bursting becomes apparent. The essential influence of an increasing pressure gradient on...

H. Werle

1984-01-01

251

Arctic aerosol size-segregated chemical observations in relation to ozone depletion during Polar Sunrise Experiment 1992  

SciTech Connect

The authors report measurements of aerosol particle size distributions and chemical compositions in the arctic winter atmosphere by means of two different impactor instruments. They looked at halogens, Na, V, As, Sb, Zn, Al, Ca, SO{sub 4}{sup 2{minus}}, Sm, K, Mn, and Mg. Several of the chemical elements were observed predominantly in particles less than 2.5 {mu}m diameter (V, Br, I, As, Sb, Zn, and SO{sub 4}{sup 2{minus}}). Cl was observed more often in larger particles relative to Na. They observed an anticorrelation between the observed occurance of Br and the measured ozone density during all observations.

Barrie, L.A.; Staebler, R.; Toom, D. [Atmospheric Environment Service, Ontario (Canada)] [and others

1994-12-20

252

In situ measurements of BrO in the Arctic stratosphere  

SciTech Connect

Mixing ratios of BrO have been measured in the Arctic lower stratosphere with an instrument mounted on the NASA ER-2 aircraft. Observations from fourteen flights above the Arctic Circle in January and February of 1989 defined mixing ratios within the vortex of 4{plus minus}2 parts per trillion by volume (pptv) at a potential temperature of 400 K, rising to 8{plus minus}2 pptv at 470 K. These values are twice as large as values found at equivalent potential temperatures at lower latitudes, and are comparable to the mixing ratios found inside the Antarctic polar vortex. Within the statistical uncertainty of the measurements, no BrO was observed in darkness at any time either inside or outside of the vortex, indicating that active bromine was sequestered in long-lived reservoirs, probably BrONO{sub 2} and BrCl. These measurements, in conjunction with measurements of ClO, demonstrate that the interaction of bromine and chlorine could represent a major sink for ozone in the presence of sunlight.

Toohey, D.W.; Anderson, J.G. (Harvard Univ., Cambridge, MA (USA)); Brune, W.H. (Pennsylvania State Univ., University Park (USA)); Chan, K.R. (NASA Ames Research Center, Mountain View, CA (USA))

1990-03-01

253

Direct Observation of Internal Spin Structure of Magnetic Vortex Cores  

Microsoft Academic Search

Thin film nanoscale elements with a curling magnetic structure (vortex) are a promising candidate for future nonvolatile data storage devices. Their properties are strongly influenced by the spin structure in the vortex core. We have used spin-polarized scanning tunneling microscopy on nanoscale iron islands to probe for the first time the internal spin structure of magnetic vortex cores. Using tips

A. Wachowiak; J. Wiebe; M. Bode; O. Pietzsch; M. Morgenstern; R. Wiesendanger

2002-01-01

254

Rapid development of arctic cyclone in June 2008 simulated by the cloud resolving global model NICAM  

NASA Astrophysics Data System (ADS)

In this study, we conducted a numerical simulation of a rapid development of an arctic cyclone (AC) that appeared in June 2008 using a cloud resolving global model, Nonhydrostatic ICosahedral Atmospheric Model (NICAM). We investigated the three dimensional structure and intensification mechanism of the simulated AC that developed to the minimum sea level pressure of 971 hPa in the model. According to the result, the AC indicates a barotropic structure with a warm core in the lower stratosphere and a cold core in the troposphere. The development of the AC is accompanied by an intense mesoscale cyclone (MC) showing baroclinic structure with a marked local arctic front. The upper level warm core of the AC is formed by an adiabatic heating associated with the downdraft in the lower stratosphere. The rapid development of the AC is caused by the combination of the intensification of the upper level warm core and the merging with the baroclinically growing MC in the lower level. The merging of the AC and MC and the vertical vortex coupling with the upper air polar vortex are the most important mechanisms for the rapid development of the arctic cyclone.

Aizawa, Takuro; Tanaka, H. L.; Satoh, Masaki

2013-09-01

255

On the influence of North Pacific sea surface temperature on the Arctic winter climate  

NASA Astrophysics Data System (ADS)

Differences between two ensembles of Goddard Earth Observing System Chemistry-Climate Model simulations isolate the impact of North Pacific sea surface temperatures (SSTs) on the Arctic winter climate. One ensemble of extended winter season forecasts is forced by unusually high SSTs in the North Pacific, while in the second ensemble SSTs in the North Pacific are unusually low. High - Low differences are consistent with a strengthened Western Pacific atmospheric teleconnection pattern, and in particular, a weakening of the Aleutian low. This relative change in tropospheric circulation inhibits planetary wave propagation into the stratosphere, in turn reducing polar stratospheric temperature in mid- and late winter. The number of winters with sudden stratospheric warmings is approximately tripled in the Low ensemble as compared with the High ensemble. Enhanced North Pacific SSTs, and thus a more stable and persistent Arctic vortex, lead to a relative decrease in lower stratospheric ozone in spring, affecting the April clear-sky UV index at Northern Hemisphere midlatitudes.

Hurwitz, M. M.; Newman, P. A.; Garfinkel, C. I.

2012-10-01

256

Health effects from long-range transported contaminants in Arctic top predators: An integrated review based on studies of polar bears and relevant model species.  

PubMed

The aim of this review is to provide a thorough overview of the health effects from the complexed biomagnified mixture of long-range transported industrial organochlorines (OCs), polybrominated diphenyl ethers (PBDEs), perfluorinated compounds (PFCs) and mercury (Hg) on polar bear (Ursus maritimus) health. Multiple scientific studies of polar bears indicate negative relationships between exposure to these contaminants and health parameters; however, these are all of a correlative nature and do not represent true cause-and-effects. Therefore, information from controlled studies of farmed Norwegian Arctic foxes (Vulpes lagopus) and housed East and West Greenland sledge dogs (Canis familiaris) were included as supportive weight of evidence in the clarification of contaminant exposure and health effects in polar bears. The review showed that hormone and vitamin concentrations, liver, kidney and thyroid gland morphology as well as reproductive and immune systems of polar bears are likely to be influenced by contaminant exposure. Furthermore, exclusively based on polar bear contaminant studies, bone density reduction and neurochemical disruption and DNA hypomethylation of the brain stem seemed to occur. The range of tissue concentration, at which these alterations were observed in polar bears, were ca. 1-70,000 ng/g lw for OCs (blood plasma concentrations of some PCB metabolites even higher), ca. 1-1000 ng/g lw for PBDEs and for PFCs and Hg 114-3052 ng/g ww and 0.1-50 microg/g ww, respectively. Similar concentrations were found in farmed foxes and housed sledge dogs while the lack of dose response designs did not allow an estimation of threshold levels for oral exposure and accumulated tissue concentrations. Nor was it possible to pinpoint a specific group of contaminants being more important than others nor analyze their interactions. For East Greenland polar bears the corresponding daily SigmaOC and SigmaPBDE oral exposure was estimated to be 35 and 0.34 microg/kg body weight, respectively. Furthermore, PFC concentrations, at which population effect levels could occur, are likely to be reached around year 2012 for the East Greenland polar bear subpopulation if current increasing temporal trends continue. Such proposed reproductive population effects were supported by physiological based pharmacokinetic (PBPK) modelling of critical body residues (CBR) with risk quotients >or=1 for SigmaPCB, dieldrin, SigmaPFC and SigmaOHC (organohalogen contaminant). The estimated daily TEQ for East Greenland polar bears and East Greenland sledge dogs were 32-281-folds above WHO SigmaTEQ guidelines for humans. Compared to human tolerable daily intake (TDI), these were exceeded for PCBs, dieldrin, chlordanes and SigmaHCH in East Greenland polar bears. Comparisons like these should be done with caution, but together with the CBR modelling and T-score estimations, these were the only available tools for polar bear risk evaluation. In conclusion, polar bears seem to be susceptible to contaminant induced stress that may have an overall sub-clinical impact on their health and population status via impacts on their immune and reproductive systems. PMID:20398940

Sonne, Christian

2010-04-15

257

The Arctic winter 2010/11 as observed by GOME-2 and SCIAMACHY and its relation to dominant modes of interannual climate variability  

NASA Astrophysics Data System (ADS)

Arctic winter-spring ozone losses in the stratosphere exhibit a large inter annual variability, emphasising that planetary wave driving largely controls magnitude as well as timing of chemically-induced losses in the stratosphere by a maintaining the strength of the polar vortex. In the course of implementing the Montreal Protocol, the release of anthropogenic long-lived ozone depleting substances into the atmosphere was greatly reduced, so that ongoing observations of stratospheric ozone suggest that the declining trend in the global ozone abundance is being reversed. However, through their long-lived nature, the reservoir of ozone killers in the upper atmosphere remains large so that one may expect that those substances may also force severe ozone losses in necessarily cold polar vortices in near future. In this work, we present a comprehensive compilation of SCIAMACHY/ENVISAT stratospheric trace gas (O3, BrO, NO2, OClO) and PSC observations during winter 2010/2011. We compare this situation of the Arctic stratosphere with that during precedent boreal winters within the SCIAMACHY period. Furthermore, we show that severe ozone losses over the Arctic are clearly associated with a characteristic evolution of the planetary wave activity in the stratosphere before and during the formation of the polar vortex, and show that this mode predominated establishes when La Niña occurred in precedent summer month.

Hommel, R.; Eichmann, K.-U.; von Savigny, C.; Weber, M.; Rozanov, A.; Richter, A.; Bramstedt, K.; Wittrock, F.; Noel, S.; Aschmann, J.; Burrows, J. P.; Graf, H. F.; Khosrawi, F.

2012-04-01

258

Vortex methods and vortex statistics.  

National Technical Information Service (NTIS)

Vortex methods originated from the observation that in incompressible, inviscid, isentropic flow vorticity (or, more accurately, circulation) is a conserved quantity, as can be readily deduced from the absence of tangential stresses. Thus if the vorticity...

A. J. Chorin

1993-01-01

259

Arctic Circle  

NSDL National Science Digital Library

Extensive information on the Arctic Circle. Highly acclaimed website features: natural resources, history and culture, society equity and environmental justice, a museum, a virtual classroom, and an Arctic forum, a discussion group for visitors. A wealth of information concerning the Arctic is at your fingertips. Site also includes information on Arctic legislation, natural resource management, stories about indigenous people, art and photo gallery, and GIS. Also features Arctic literature, music, and media.

260

Vortex methods and vortex statistics  

SciTech Connect

Vortex methods originated from the observation that in incompressible, inviscid, isentropic flow vorticity (or, more accurately, circulation) is a conserved quantity, as can be readily deduced from the absence of tangential stresses. Thus if the vorticity is known at time t = 0, one can deduce the flow at a later time by simply following it around. In this narrow context, a vortex method is a numerical method that makes use of this observation. Even more generally, the analysis of vortex methods leads, to problems that are closely related to problems in quantum physics and field theory, as well as in harmonic analysis. A broad enough definition of vortex methods ends up by encompassing much of science. Even the purely computational aspects of vortex methods encompass a range of ideas for which vorticity may not be the best unifying theme. The author restricts himself in these lectures to a special class of numerical vortex methods, those that are based on a Lagrangian transport of vorticity in hydrodynamics by smoothed particles (``blobs``) and those whose understanding contributes to the understanding of blob methods. Vortex methods for inviscid flow lead to systems of ordinary differential equations that can be readily clothed in Hamiltonian form, both in three and two space dimensions, and they can preserve exactly a number of invariants of the Euler equations, including topological invariants. Their viscous versions resemble Langevin equations. As a result, they provide a very useful cartoon of statistical hydrodynamics, i.e., of turbulence, one that can to some extent be analyzed analytically and more importantly, explored numerically, with important implications also for superfluids, superconductors, and even polymers. In the authors view, vortex ``blob`` methods provide the most promising path to the understanding of these phenomena.

Chorin, A.J.

1993-05-01

261

Magnetic vortex dynamics induced by an electrical current  

NASA Astrophysics Data System (ADS)

A magnetic nanoparticle in a vortex state is a promising candidate for the information storage. One bit of information corresponds to the upward or downward magnetization of the vortex core (vortex polarity). The dynamics of the magnetic vortex driven by a spin current is studied theoretically. Using a simple analytical model and numerical simulations, we show that a nondecaying vortex motion can be excited by a dc spin-polarized current, whose intensity exceeds a first threshold value as a result of the balance between a spin-torque pumping and damping forces. The irreversible switching of the vortex polarity takes place for a current above a second threshold. The mechanism of the switching, which involves the process of creation and annihilation of a vortex-antivortex pair is described analytically, using a rigid model, and confirmed by detailed spin-lattice simulations.

Gaididei, Yuri; Kravchuk, Volodymyr P.; Sheka, Denis D.

262

Chlorine activation and chemical ozone loss deduced from HALOE and balloon measurements in the Arctic during the winter of 1999-2000  

NASA Astrophysics Data System (ADS)

We employ Halogen Occultation Experiment (HALOE) observations and balloon-borne measurements (on the large Observations of the Middle Stratosphere [OMS] and Triple balloons, as well as on two small balloons) to investigate ozone loss in the stratospheric vortex in the 1999-2000 Arctic winter. Using HF and CH4 as long-lived tracers, we identify chlorine activation and chemical ozone destruction in the polar vortex. Reference relations, representative of chemically undisturbed "early vortex" conditions, are derived from the OMS remote and in situ balloon measurements on 19 November and 3 December 1999, respectively. Deviations from this "early vortex" reference are interpreted as chemical ozone loss and heterogeneous chlorine activation. The observations show an extensive activation of chlorine; in late February 2000, the activation extends to altitudes of 600 K. Between 360 and 450 K chlorine was almost completely activated. At that time, about 70% of the HCl column between 380 and 550 K was converted to active chlorine. Furthermore, the measurements indicate severe chemical ozone loss, with a maximum loss of over 60% in the lower stratosphere (415-465 K) by mid-March 2000. Substantial ozone loss was still observable in vortex remnants in late April 2000 (80 ± 10 Dobson units [DU] between 380 and 550 K). The average loss in column ozone between 380 and 550 K, inside the vortex core, in mid-March amounted to 84 ± 13 DU.

Müller, Rolf; Tilmes, Simone; Grooß, Jens-Uwe; McKenna, Daniel S.; Müller, Melanie; Schmidt, Ulrich; Toon, Geoffrey C.; Stachnik, Robert A.; Margitan, James J.; Elkins, James W.; Arvelius, Johan; Russell, James M.

2002-03-01

263

Chlorine activation and chemical ozone loss deduced from HALOE and balloon measurements in the Arctic during the winter of 1999-2000  

NASA Astrophysics Data System (ADS)

We employ Halogen Occultation Experiment (HALOE) observations and balloon-borne measurements (on the large Observations of the Middle Stratosphere [OMS] and Triple balloons, as well as on two small balloons) to investigate ozone loss in the stratospheric vortex in the 1999-2000 Arctic winter. Using HF and CH4 as long-lived tracers, we identify chlorine activation and chemical ozone destruction in the polar vortex. Reference relations, representative of chemically undisturbed ``early vortex'' conditions, are derived from the OMS remote and in situ balloon measurements on 19 November and 3 December 1999, respectively. Deviations from this ``early vortex'' reference are interpreted as chemical ozone loss and heterogeneous chlorine activation. The observations show an extensive activation of chlorine; in late February 2000, the activation extends to altitudes of 600 K. Between 360 and 450 K chlorine was almost completely activated. At that time, about 70% of the HCl column between 380 and 550 K was converted to active chlorine. Furthermore, the measurements indicate severe chemical ozone loss, with a maximum loss of over 60% in the lower stratosphere (415-465 K) by mid-March 2000. Substantial ozone loss was still observable in vortex remnants in late April 2000 (80 +/- 10 Dobson units [DU] between 380 and 550 K). The average loss in column ozone between 380 and 550 K, inside the vortex core, in mid-March amounted to 84 +/- 13 DU.

Müller, Rolf; Tilmes, Simone; Grooß, Jens-Uwe; McKenna, Daniel S.; Müller, Melanie; Schmidt, Ulrich; Toon, Geoffrey C.; Stachnik, Robert A.; Margitan, James J.; Elkins, James W.; Arvelius, Johan; Russell, James M.

2003-03-01

264

Polar Bear  

USGS Publications Warehouse

Polar bears are long-lived, late-maturing carnivores that have relatively low rates of reproduction and natural mortality. Their populations are susceptible to disturbance from human activities, such as the exploration and development of mineral resources or hunting. Polar bear populations have been an important renewable resource available to coastal communities throughout the Arctic for thousands of years.

Amstrup, S. D.; DeMaster

1988-01-01

265

Magnetic vortex dynamics in elliptical dots: Field dependence and interaction effects  

Microsoft Academic Search

This study aims to investigate experimentally the dynamics of magnetic vortices and vortex pairs confined in lithographically defined Permalloy ellipses using microwave reflection technique. The single vortex magnetization state exhibits a single, low frequency peak in the impedance derivative spectrum for a given external field. Experimental results show that vortex polarization dominates the vortex dynamics while it plays a negligible

K. S. Buchanan; P. E. Roy; M. Grimsditch; E. Y. Fradin; K. Y. Guslienko; S. D. Bader; V. Novosad

2006-01-01

266

Dynamics of the exceptional warming events during the Arctic winters 2003/04, 2005/06 and 2008/09  

NASA Astrophysics Data System (ADS)

Sudden stratospheric warmings (SSW) are common features of the Arctic meteorology. During a major SSW, polar temperature rises and the zonal mean flow weakens dramatically over a short period of time. This situation causes displacement, distortion or split of the polar vortex. The Arctic winters 2003/04, 2005/06 and 2008/09 were characterized by major midwinter warming of different proportions. The major warming occurred in early January in 2003/04 and in mid-January in the other winters in the lower stratosphere. The winter 2003/04 was remarkable in that a stable vortex formed again in March 2004 after two months of severe disturbance. No vortex was evident in other winters after the mid-January major warming. The planetary waves 1 and 2 play a key role in warming events and in vortex distortions as they control the stratospheric circulation. The dominating presence and amplitude of these waves were also different in each winter. In this presentation, we characterize the winters 2003/04, 2005/06 and 2008/09 in terms of chemical and dynamical situation during the winters. In order to illustrate, we exploit the heat flux, zonal wind characteristics, Eliassen-Palm vectors and planetary wave analyzes for the winters in a comparative perspective. The dynamical parameters are derived from ECMWF analyzes and the chemical realm are discussed in terms of the measurements from MLS (Microwave Limb Sounder) and POAM (Polar Ozone and Aerosol Measurement) as well as simulations from the Mimosa-Chim global three-dimensional chemical transport model.

Kuttippurath, Jayanarayanan; Godin-Beekmann, Sophie; Lefèvre, Franck; Nikulin, Grigory

2010-05-01

267

Arctic stratospheric dehydration - Unprecedented observations and microphysical modeling study  

NASA Astrophysics Data System (ADS)

Polar stratospheric clouds (PSCs) may form in the lower stratosphere above the winter poles at sufficiently low temperatures. Ice PSCs require the coldest conditions, with temperatures some degrees below the frost point to nucleate ice particles. When the particles grow to sizes large enough to sediment, they may result in dehydration, i.e. irreversible redistribution of water vapor, as it frequently occurs above the Antarctic. Conversely, there are no observations above the Arctic that would have provided clear evidence for vertical redistribution of water vapor. Here we report on unequivocal in situ observations in January 2010 above Sodankylä, Finland, which mesh with vortex-wide satellite measurements. Within the LABPIAT-II field campaign, a series of balloon-borne aerosol backscatter and water vapor measurements has been performed. The balloon payload comprised the backscatter sonde COBALD in combination with the cryogenic frost point hygrometer CFH and the fluorescent Lyman-Alpha stratospheric hygrometer FLASH-B. Together with satellite measurements from the Aura microwave limb sounder MLS and the cloud-aerosol lidar CALIOP, a unique and coherent picture of de- and rehydration in the Arctic vortex will be presented within this paper. An extensive coverage of synoptic scale ice PSCs has been observed by CALIOP and COBALD by mid-January due to exceptionally low temperatures in the Arctic vortex. This observation goes along with a simultaneously measured strong reduction in water vapor by 1.6 ppmv relative to background conditions. Subsequent sedimentation and sublimation of ice particles led to a vertical redistribution of water inside the vortex, which was tracked remotely and could be quantified again by in situ measurements some five days later. By means of a microphysical column model, we are able to connect the individual balloon soundings by trajectories and simulate the formation, evolution and sedimentation of the ice particles. Simulated water vapor profiles are verified by CFH, FLASH-B and MLS measurements. Optical T-Matrix calculations enable us to additionally compare the simulations with COBALD and CALIOP backscatter measurements. We examine the effect of different PSC formation pathways - in particular homogeneous vs. heterogeneous ice formation - and changing temperatures and finally show that synoptic scale ice PSCs and concurrent reduction in water vapor are tightly linked with the observed de- and rehydration signatures.

Engel, Ines; Luo, Beiping P.; Khaykin, Sergey; Wienhold, Frank G.; Vömel, Holger; Kivi, Rigel; Pitts, Michael C.; Poole, Lamont R.; Santee, Michelle L.; Grooß, Jens-Uwe; Peter, Thomas

2013-04-01

268

Arctic Story Puzzles  

NSDL National Science Digital Library

This activity has three story puzzles learners can solve to learn about life in the Arctic. Through this story-sequencing activity, learners will explore how life for polar bears and the native Inuit people is being affected by climate change. Activity includes three puzzles as PDF files.

History, American M.

2007-01-01

269

A vortex-scale simulation of the growth and sedimentation of large nitric acid hydrate particles  

NASA Astrophysics Data System (ADS)

Nitric acid-containing particles with diameters of 10-20 ?m were detected inside the Arctic polar vortex in the period January to March 2000. We present the results of a unique three-dimensional microphysical simulation of these large HNO3-containing particles covering the entire Arctic vortex. The model describes the simultaneous growth, evaporation, sedimentation, and advection of several thousand individual nitric acid hydrate particles over their complete lifetime. We compare modeled and observed particle size distributions as a test of different particle nucleation mechanisms. The model is able to produce particles with sizes typical of those observed and broadly reproduces the change in particle characteristics through the winter assuming nitric acid trihydrate (NAT) particle growth. The possibility that the observed large nitric acid-containing particles were composed of nitric acid dihydrate (NAD) cannot be excluded within the uncertainty of the HNO3 field above the aircraft. The formation of nitric acid hydrate particles on synoptic ice clouds may be a source of some of the observed large nitric acid-containing particles. However, a direct, but highly selective, nucleation of NAT or NAD particles over wide regions appears to be necessary to explain the observations.

Carslaw, Kenneth S.; Kettleborough, Jamie A.; Northway, Megan J.; Davies, Stewart; Gao, Ru-Shan; Fahey, David W.; Baumgardner, Darrel G.; Chipperfield, Martyn P.; KleinböHl, Armin

2002-10-01

270

Electric spectroscopy of vortex states and dynamics in magnetic disks  

NASA Astrophysics Data System (ADS)

Spin-polarized radio frequency (RF) currents and RF-Oersted fields resonantly excite a magnetic vortex core confined in a micron-scale soft magnetic disk. In this study, we measured the rectifying voltage spectra caused by the anisotropic magnetoresistance oscillation due to the gyration of the vortex with different polarity and chirality. The measured spectra are presented such that we can determine the vortex properties and strength of the spin torques and Oersted field accurately and directly through analytical calculation.

Goto, Minori; Hata, Hiroshi; Yamaguchi, Akinobu; Nakatani, Yoshinobu; Yamaoka, Takehiro; Nozaki, Yukio; Miyajima, Hideki

2011-08-01

271

Live from the Arctic  

NASA Astrophysics Data System (ADS)

For reasons of geography and geophysics, the poles of our planet, the Arctic and Antarctica, are places where climate change appears first: they are global canaries in the mine shaft. But while Antarctica (its penguins and ozone hole, for example) has been relatively well-documented in recent books, TV programs and journalism, the far North has received somewhat less attention. This project builds on and advances what has been done to date to share the people, places, and stories of the North with all Americans through multiple media, over several years. In a collaborative project between the Arctic Research Consortium of the United States (ARCUS) and PASSPORT TO KNOWLEDGE, Live from the Arctic will bring the Arctic environment to the public through a series of primetime broadcasts, live and taped programming, interactive virtual field trips, and webcasts. The five-year project will culminate during the 2007-2008 International Polar Year (IPY). Live from the Arctic will: A. Promote global understanding about the value and world -wide significance of the Arctic, B. Bring cutting-edge research to both non-formal and formal education communities, C. Provide opportunities for collaboration between arctic scientists, arctic communities, and the general public. Content will focus on the following four themes. 1. Pan-Arctic Changes and Impacts on Land (i.e. snow cover; permafrost; glaciers; hydrology; species composition, distribution, and abundance; subsistence harvesting) 2. Pan-Arctic Changes and Impacts in the Sea (i.e. salinity, temperature, currents, nutrients, sea ice, marine ecosystems (including people, marine mammals and fisheries) 3. Pan-Arctic Changes and Impacts in the Atmosphere (i.e. precipitation and evaporation; effects on humans and their communities) 4. Global Perspectives (i.e. effects on humans and communities, impacts to rest of the world) In The Earth is Faster Now, a recent collection of comments by members of indigenous arctic peoples, arctic residents speak in eloquent terms of the changes they see around them, manifested in new patterns of vegetation, the melting of permafrost and the absence of game species that used to be abundant. Meanwhile, new satellites and more sophisticated sensors on the ground and in the ice, add scientific testimony that seems to support and even extend native perceptions. Live from the Arctic will unify both perspectives, and use todays most powerful and effective communications media to connect young people and general audiences all across America to researchers and communities living and working in the Arctic. During IPY there will be a level of interest in the Polar regions unprecedented in a generation. Live from the Arctic offers unique resources to satisfy that curiosity, and encourage active participation and engagement in understanding some of Earths most significant peoples, places and rapidly changing conditions.

Warnick, W. K.; Haines-Stiles, G.; Warburton, J.; Sunwood, K.

2003-12-01

272

Temporal trends of perfluoroalkyl contaminants in polar bears (Ursus maritimus) from two locations in the North American Arctic, 1972-2002.  

PubMed

Perfluoroalkyl substances are globally distributed anthropogenic contaminants. Their production and use have increased dramatically from the early 1980s. While many recent publications have reported concentrations of perfluorooctane sulfonate (PFOS) and other perfluoroalkyl acids (PFAs) in biotic and abiotic samples, only limited work has addressed temporal trends. In this study we analyzed archived polar bear(Ursus maritimus) livertissue samples from two geographic locations in the North American Arctic, collected from 1972 to 2002. The eastern group, taken from the vicinity of northern Baffin Island, Canada, comprised 31 samples, and the western group, from the vicinity of Barrow, Alaska, comprised 27 samples. Samples were analyzed for perfluorocarboxylic acids (PFCAs) from carbon chain length C8 to C15, perfluorohexane sulfonate, PFOS, the neutral precursor perfluorooctane sulfonamide (PFOSA), as well as 8:2 and 10:2 fluorotelomer acids and their alpha,beta unsaturated acid counterparts. Concentrations of PFOS and PFCAs with carbon chain lengths from C9 to C11 showed an exponential increase between 1972 and 2002 at both locations. Doubling times ranged from 3.6 +/- 0.9 years for perfluorononanoic acid in the eastern group to 13.1 +/- 4.0 years for PFOS in the western group. PFOSA showed decreasing concentrations over time at both locations, while the remaining PFAs showed no significant trends or were not detected in any sample. The doubling time for PFOS was similar to the doubling time of production of perfluoroctylsulfonyl-fluoride-based products during the 1990s. PMID:16572767

Smithwick, Marla; Norstrom, Ross J; Mabury, Scott A; Solomon, Keith; Evans, Thomas J; Stirling, Ian; Taylor, Mitch K; Muir, Derek C G

2006-02-15

273

Organochlorines in antarctic and arctic avian top predators: a comparison between the South Polar Skua and two species of northern hemisphere gulls.  

PubMed

Different organochlorine compounds (OCs) were measured in the blood of breeding south polar skuas (Catharacta maccormicki) at Svarthamaren, Dronning Maud Land (Antarctica) and compared to those in two species of northern hemisphere gulls: the Arctic glaucous gull (Larus hyperboreus) and the subarctic great black-backed gull (Larus marinus). The skuas had 8% and 29% of the SigmaOC levels (45 ng/g, wet weight) of glaucous gulls (591 ng/g) and great black-backed gulls (158 ng/g), respectively. Polychlorinated biphenyls (PCBs) and p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) were very low in skuas compared to northern gulls, but the mean hexachlorobenzene (HCB) level was 1.7 times higher than in great black-backed gulls and one-third of the glaucous gull level. Mirex levels in skuas were among the highest reported in birds, the mean level being 3 and 26 times higher than those in glaucous gull and great black-backed gulls, respectively. In skuas, the mean levels of HCB, oxychlordane, p,p'-DDE, and PCBs increased by about 30% during a 2-week period, and mirex increased by nearly 60%. In glacuous gulls, HCB, p,p'-DDE, and PCBs increased by 10-20%. For HCB, mirex, and oxychlordane, only a relatively small proportion of the increase in skuas could be explained by changes in lipid pools and the levels at first sampling, compared to glaucous gulls. Thus, skuas were probably accumulating these compounds when present in Antarctica. p,p'-DDE and PCB levels, in contrast, seemed much more stable in the skuas. Relatively high levels of mirex and HCB in south polar skuas are concerning with regard to potential adverse effects. PMID:16683630

Bustnes, Jan O; Tveraa, Torkild; Henden, John A; Varpe, Oystein; Janssen, Kirstin; Skaare, Janneche U

2006-04-15

274

Decadal Time Scale change in terrestrial plant communities in North American arctic and alpine tundra: A contribution to the International Polar Year Back to the Future Project (Invited)  

NASA Astrophysics Data System (ADS)

The International Polar Year-Back to the Future (IPY-BTF) is an endorsed International Polar Year project (IPY project #214). The overarching goal of this program is to determine how key structural and functional characteristics of high latitude/altitude terrestrial ecosystems have changed over the past 25 or more years and assess if such trajectories of change are likely to continue in the future. By rescuing data, revisiting, re-sampling historic research sites and assessing environmental change over time, we aim to provide greater understanding of how tundra is changing and what the possible drivers of these changes are. Resampling of sites established by Patrick J. Webber between 1964 and 1975 in northern Baffin Island, Northern Alaska and in the Rocky Mountains form a key contribution to the BTF project. Here we report on resampling efforts at each of these locations and initial results of a synthesis effort that finds similarities and differences in change between sites. Results suggest that although shifts in plant community composition are detectable at each location, the magnitude and direction of change differ among locations. Vegetation shifts along soil moisture gradients is apparent at most of the sites resampled. Interestingly, however, wet communities seem to have changed more than dry communities in the Arctic locations, while plant communities at the alpine site appear to be becoming more distinct regardless of soil moisture status. Ecosystem function studies performed in conjunction with plant community change suggest that there has been an increase in plant productivity at most sites resampled, especially in wet and mesic land cover types.

Tweedie, C. E.; Ebert-May, D.; Hollister, R. D.; Johnson, D. R.; Lara, M. J.; Villarreal, S.; Spasojevic, M.; Webber, P.

2010-12-01

275

Chlorinated Hydrocarbon Contaminants in Polar Bears from Eastern Russia, North America, Greenland, and Svalbard: Biomonitoring of Arctic Pollution  

Microsoft Academic Search

.   Adipose tissue samples from polar bears (Ursus maritimus) were obtained by necropsy or biopsy between the spring of 1989 to the spring of 1993 from Wrangel Island in Russia, most\\u000a of the range of the bear in North America, eastern Greenland, and Svalbard. Samples were divided into 16 regions corresponding\\u000a as much as possible to known stocks or management

R. J. Norstrom; S. E. Belikov; E. W. Born; G. W. Garner; B. Malone; S. Olpinski; M. A. Ramsay; S. Schliebe; I. Stirling; M. S. Stishov; M. K. Taylor; Ø. Wiig

1998-01-01

276

Arctic deployment of USCGC Polar Sea - winter 1983. Volume 3. Trafficability tests. Final report, December 1982November 1983  

Microsoft Academic Search

Environmental and ship-performance data were collected aboard the USCGC POLAR SEA during the period March-May 1983 as part of a multi-year program to make an operational assessment on the feasibility of a year-round marine transportation system (including offshore structures) serving Alaska. This is the third volume of a four-volume set and focuses on the performance of the icebreaker from the

R. P. Voelker; F. A. Geisel; K. E. Dane

1983-01-01

277

Arctic Research and Writing  

NSDL National Science Digital Library

Recently, senior-level physics students joined thousands of scientists from over 60 nations to examine a wide range of physical, biological, and social research topics as part of the International Polar Year (IPY). Through a National Science Foundation (NSF)-funded research project, these students applied physics concepts to the study of Arctic sea ice. They participated in an authentic proposal writing contest focused on dramatic changes observed in the Arctic environment and developed a research question to examine why these changes are occurring. This article describes their participation in this exciting hands-on project.

Coon, Brian; Englert, Karl; Hinckley, Matt; Pruis, Matt

2009-01-01

278

Verification of Vortex Workflows  

Microsoft Academic Search

Vortex is a workflow language to support decision making activities. It centers around gathering and computing attributes of in- put objects. The semantics of Vortex is declarative, and the dependency graphs of Vortex programs are acyclic. This paper discusses the appli- cation of symbolic model checking techniques to verification of Vortex programs. As a case study we used a Vortex

Xiang Fu; Tevfik Bultan; Richard Hull; Jianwen Su

2001-01-01

279

First measurements of ClOOCl in the stratosphere: The coupling of ClOOCl and ClO in the Arctic polar vortex  

Microsoft Academic Search

simultaneously. Observations of the ratio (ClOOCl)\\/(ClO)2 (estimated uncertainty of ±25%, 1 s) are used with a time-dependent photochemical model, to test the model representationoftheratiosofkineticparametersJ\\/kProdandkLoss\\/kProdfordayandnighttime observations, respectively. Here, kProd and kLoss are the rate constants for ClOOCl

R. M. Stimpfle; D. M. Wilmouth; R. J. Salawitch; J. G. Anderson

2004-01-01

280

First measurements of ClOOCl in the stratosphere: The coupling of ClOOCl and ClO in the Arctic polar vortex  

Microsoft Academic Search

The first measurements of ClOOCl in the stratosphere have been acquired from a NASA ER-2 aircraft, deployed from Kiruna, Sweden (68°N, 21°E), during the joint SOLVE\\/THESEO-2000 mission of the winter of 1999\\/2000. ClOOCl is detected by thermal dissociation into two ClO fragments that are measured by the well-known technique of chemical conversion, vacuum ultraviolet resonance fluorescence. Ambient ClO is detected

R. M. Stimpfle; D. M. Wilmouth; R. J. Salawitch; J. G. Anderson

2004-01-01

281

Using 10Be dating to pace Laurentide Ice Sheet retreat in polar landscapes: Rapid fiord deglaciation on Baffin Island, Arctic Canada  

NASA Astrophysics Data System (ADS)

The retreat of the last great ice sheets during latest Pleistocene/Holocene warming serves as an analog for contemporary ice sheet response to climate change. Although cosmogenic exposure dating has recently led to improvements in ice sheet retreat chronologies, isotope inheritance has complicated its use in polar landscapes. The application of cosmogenic isotopes to the history and behavior of the northeastern Laurentide Ice Sheet on Baffin Island, Arctic Canada, over the last decade has led to four key insights. First, differential erosion by polythermal ice sheet conditions has led to a complicated pattern of cosmogenic isotope concentration in eastern Baffin Island landscapes. Second, cosmogenic isotopes inherited in locations not significantly eroded provide more information about ice sheet erosion (and burial) than chronology. Third, bedrock suitable for exposure dating commonly only occurs in valley bottoms that experienced significant erosion. Four, erratics in landscapes of insignificant erosion can sometimes be suitable samples for exposure dating. Building on these lessons, we highlight recent efforts to constrain retreat chronology in fiords of eastern Baffin Island. 10Be dating of glacially-polished low-elevation bedrock spanning 120 km of Sam Ford Fiord reveals 80 km of retreat in <1000 years at ~9.5 ka. Deglaciation began prior to 15 ka from a glacial maximum margin on the continental shelf, and the modern Barnes Ice Cap margin, 30 km inland from the head of Sam Ford Fiord, was attained in the late Holocene. Thus, over half of overall ice margin retreat since the last glacial maximum occurred in less than 10% of the deglacial interval. This rapid deglaciation was likely caused by a combination of climate-forced retreat and increased calving rates in up to 900-m-deep water. Although adjacent fiord mouths deglaciated earlier than at Sam Ford Fiord, the middle reaches of all fiords that we have studied along northeastern Baffin Island experienced rapid deglaciation between 10 and 9 ka. Constraining more precise rates of such rapid deglaciation is difficult with 10Be dating, but a similar magnitude of retreat of present ice streams like Greenland's Jakobshavn Isbrae, which occupies a long and deep fiord similar in geometry to those on Baffin Island, is likely if the Arctic continues to warm.

Briner, J. P.; Bini, A. C.; Anderson, R. S.; Davis, P. T.; Miller, G. H.

2008-12-01

282

Brownian vortexes  

NASA Astrophysics Data System (ADS)

Mechanical equilibrium at zero temperature does not necessarily imply thermodynamic equilibrium at finite temperature for a particle confined by a static but nonconservative force field. Instead, the diffusing particle can enter into a steady state characterized by toroidal circulation in the probability flux, which we call a Brownian vortex. The circulatory bias in the particle’s thermally driven trajectory is not simply a deterministic response to the solenoidal component of the force but rather reflects interplay between advection and diffusion in which thermal fluctuations extract work from the nonconservative force field. As an example of this previously unrecognized class of stochastic heat engines, we consider a colloidal sphere diffusing in a conventional optical tweezer. We demonstrate both theoretically and experimentally that nonconservative optical forces bias the particle’s fluctuations into toroidal vortexes whose circulation can reverse direction with temperature or laser power.

Sun, Bo; Lin, Jiayi; Darby, Ellis; Grosberg, Alexander Y.; Grier, David G.

2009-07-01

283

Sensitivity of an Arctic regional climate model to the horizontal resolution during winter: implications for aerosol simulation  

NASA Astrophysics Data System (ADS)

Our ability to properly simulate current climate and its future change depends upon the exactitude of the physical processes that are parameterized on the one hand, and on model configuration on the other hand. In this paper, we focus on the latter and investigate the effect of the horizontal grid resolution on the simulation of a month of January over the Arctic. A limited-area numerical climate model is used to simulate the month of January 1990 over a grid that includes the Arctic and sub-Arctic regions. Two grid resolutions are used: 50 km and 100 km. Results show that finer details appear for regional circulation, temperature, and humidity when increasing horizontal resolution. This is particularly true for continental and sea ice boundaries, which are much better resolved by high-resolution model simulations. The Canadian Archipelago and rivers in northern Russia appear to benefit the most from higher horizontal resolution. High-resolution simulations capture some frozen rivers and narrow straits between islands. Therefore, much colder surface air temperature is simulated over these areas. Precipitation is generally increased in those areas and over topography due to a better representation of surface heterogeneities when increasing resolution. Large-scale atmospheric circulation is substantially changed when horizontal resolution is increased. Feedback processes occur between surface air temperature change over heterogeneous surfaces and atmospheric circulation. High-resolution simulations develop a stronger polar vortex. The mean sea-level pressure increases over the western Arctic and Iceland and decreases over the eastern Arctic. This circulation leads to a substantial cooling of the eastern Arctic and enhanced synoptic activity over the Arctic associated with an intensification of the baroclinic zone. Aerosol mass loading, which is simulated explicitly in this model, is significantly altered by the grid resolution change with the largest differences in aerosol concentration over areas where precipitation and atmospheric circulation are the most affected. The implications of this sensitivity study to the evaluation of indirect radiative effects of anthropogenic aerosols are discussed.

Girard, Eric; Bekcic, Biljana

2005-09-01

284

Air-water exchange of anthropogenic and natural organohalogens on International Polar Year (IPY) expeditions in the Canadian Arctic.  

PubMed

Shipboard measurements of organohalogen compounds in air and surface seawater were conducted in the Canadian Arctic in 2007-2008. Study areas included the Labrador Sea, Hudson Bay, and the southern Beaufort Sea. High volume air samples were collected at deck level (6 m), while low volume samples were taken at 1 and 15 m above the water or ice surface. Water samples were taken within 7 m. Water concentration ranges (pg L(-1)) were as follows: ?-hexachlorocyclohexane (?-HCH) 465-1013, ?-HCH 150-254, hexachlorobenzene (HCB) 4.0-6.4, 2,4-dibromoanisole (DBA) 8.5-38, and 2,4,6-tribromoanisole (TBA) 4.7-163. Air concentration ranges (pg m(-3)) were as follows: ?-HCH 7.5-48, ?-HCH 2.1-7.7, HCB 48-71, DBA 4.8-25, and TBA 6.4 - 39. Fugacity gradients predicted net deposition of HCB in all areas, while exchange directions varied for the other chemicals by season and locations. Net evasion of ?-HCH from Hudson Bay and the Beaufort Sea during open water conditions was shown by air concentrations that averaged 14% higher at 1 m than 15 m. No significant difference between the two heights was found over ice cover. The ?-HCH in air over the Beaufort Sea was racemic in winter (mean enantiomer fraction, EF = 0.504 ± 0.008) and nonracemic in late spring-early summer (mean EF = 0.476 ± 0.010). This decrease in EF was accompanied by a rise in air concentrations due to volatilization of nonracemic ?-HCH from surface water (EF = 0.457 ± 0.019). Fluxes of chemicals during the southern Beaufort Sea open water season (i.e., Leg 9) were estimated using the Whitman two-film model, where volatilization fluxes are positive and deposition fluxes are negative. The means ± SD (and ranges) of net fluxes (ng m(-2) d(-1)) were as follows: ?-HCH 6.8 ± 3.2 (2.7-13), ?-HCH 0.76 ± 0.40 (0.26-1.4), HCB -9.6 ± 2.7 (-6.1 to -15), DBA 1.2 ± 0.69 (0.04-2.0), and TBA 0.46 ± 1.1 ng m(-2) d(-1) (-1.6 to 2.0). PMID:21194218

Wong, Fiona; Jantunen, Liisa M; Pu?ko, Monika; Papakyriakou, Tim; Staebler, Ralf M; Stern, Gary A; Bidleman, Terry F

2010-12-31

285

The surface UV-B irradiation in the Arctic: observations at the Polish polar station, Hornsund /(77°N,15°E), 1996-1997  

NASA Astrophysics Data System (ADS)

Measurements of the UV-B radiation reaching ground level at the Polish polar station, Hornsund (Svalbard, 77°N, /15°30'E, 11 m a.s.l.), have been carried out since February 1996 by means of a temperature stabilized Robertson-Berger-type meter. The seasonal pattern of UV dose and UV index, and factors affecting the UV-B level there are studied for the period March-October of 1996 and 1997. The quality of the UV measurements is assured by comparisons of the instrument readings with those calculated from a radiative transfer model under clear-sky conditions. A statistical method is proposed to examine the year-to-year drift of the instrument readings. The maximum value of UV daily dose and UV index are found in late spring of 10.2 MED (1MED=210Jeffm-2) and 2.5, respectively. The maximum UV irradiance at the midnight is ?4mWeffm-2. The seasonal pattern of UV daily dose appears to be asymmetric relative to the summer solstice. All-weather UV measurements taken in early spring provided much higher /(?50%) UV irradiances than the corresponding measurements in late summer because of larger ground albedo and atmospheric transparency (due to smaller cloud//aerosol optical depth) in early spring. Depletion of total ozone is not the only source of the UV trend over Arctic. It is found that long-term (1965-1997) changes in the cloud cover over southern Svalbard had significant impact on the UV level there.

Krzy?cin, J. W.; S. Sobolewski, P.

2001-03-01

286

Airborne passive microwave measurements of arctic clouds and sea ice  

Microsoft Academic Search

Characterization of arctic cloud processes, although important for many applications, remains a difficult challenge. Few in situ observations of arctic clouds are available, and satellite retrieval of polar cloud properties has not been as successful as in other parts of the world. The purpose of this work is to investigate the feasibility of relating liquid water path in arctic clouds

Julie Anne Haggerty

2001-01-01

287

Chemical depletion of Arctic ozone in winter 1999\\/2000  

Microsoft Academic Search

During Arctic winters with a cold, stable stratospheric circulation, reactions on the surface of polar stratospheric clouds (PSCs) lead to elevated abundances of chlorine monoxide (ClO) that, in the presence of sunlight, destroy ozone. Here we show that PSCs were more widespread during the 1999\\/2000 Arctic winter than for any other Arctic winter in the past two decades. We have

M. Rex; R. J. Salawitch; N. R. P. Harris; P. von der Gathen; G. O. Braathen; A. Schulz; H. Deckelmann; M. Chipperfield; B.-M. Sinnhuber; E. Reimer; R. Alfier; R. Bevilacqua; K. Hoppel; M. Fromm; J. Lumpe; H. Küllmann; A. Kleinböhl; H. Bremer; M. von König; K. Künzi; D. Toohey; H. Vömel; E. Richard; K. Aikin; H. Jost; J. B. Greenblatt; M. Loewenstein; J. R. Podolske; C. R. Webster; G. J. Flesch; D. C. Scott; R. L. Herman; J. W. Elkins; E. A. Ray; F. L. Moore; D. F. Hurst; P. Romashkin; G. C. Toon; B. Sen; J. J. Margitan; P. Wennberg; R. Neuber; M. Allart; B. R. Bojkov; H. Claude; J. Davies; W. Davies; H. De Backer; H. Dier; V. Dorokhov; H. Fast; Y. Kondo; E. Kyrö; Z. Litynska; I. S. Mikkelsen; M. J. Molyneux; E. Moran; T. Nagai; H. Nakane; C. Parrondo; F. Ravegnani; P. Skrivankova; P. Viatte; V. Yushkov

2002-01-01

288

On the atmospheric transport of pollution to the Arctic  

Microsoft Academic Search

If the atmospheric processes are assumed to be nearly adiabatic, the conclusion is that the possible source areas of Arctic air pollution detected at ground level have to be situated in areas with almost the same temperature as observed in the Arctic itself. Sources south of the polar front system can only contribute to high-altitude (or upper level) Arctic pollution.

Trond Iversen

1984-01-01

289

Rejuvenation of Arctic Sea Ice and Tropospheric Chemical Change  

NASA Astrophysics Data System (ADS)

The Arctic sea ice cover has been transformed by a vast replacement of older perennial sea ice to younger seasonal ice. This rejuvenation results in an immense and relatively salty seasonal ice cover impacting chemical processes in the Arctic troposphere during the polar sun rise period. New results from the QuikSCAT satellite scatterometer (QS) show that March perennial ice extent remained low in 2010. In November 2009, the QS antenna was stuck in one azimuth direction after more than 10 years in orbit. Nevertheless, the scatterometer is still working to collect good global backscatter data although with a much reduced swath. Thus, the climatic data record of Arctic perennial ice extent in the 2000s (2000-2009) can be continued into 2010 and beyond if the QS scatterometer is kept in continuous operation, a concept we refer to as the Polar Express Mission. These measurements, in combination with those from AMSR-E radiometers, ice charts, and surface buoys, represent important complementary data to characterize the state of Arctic sea ice in the present and also in a long-term perspective. Measurements of atmospheric chemicals have been collected by satellites (e.g., OMI, GOME, GOME-2, and SCIAMACHY) and by field experiments (e.g., OASIS and CFL) and from recent deployments of O-buoys. Results show a consistency in the timing of bromine-increase episodes between satellite and field observations in March 2008. The Rising Air Parcel model reveals tropospheric patterns, under control of the regional topography, conform well to the pattern of bromine monoxide (BrO) measured by satellites. Atmospheric patterns from the low troposphere to the stratosphere are reconstructed using 3D wind fields. These results reveal the dynamic control of the wind patterns on BrO distribution in the lower troposphere, explaining the vortex and the split in the observed BrO pattern in the Beaufort Sea, while the patterns become uncorrelated in the stratosphere. Intense episodes of bromine explosions occurred in March-May in 2009 and again in 2010, when there were vast regions of seasonal sea ice and low ice surface temperature (from MODIS data). Bromine explosions with associated ozone and gaseous elementary mercury depletions can impact the atmospheric chemical and radiative balance and the rate of deposition of mercury to the Arctic Ocean surface.

Nghiem, S. V.; Rigor, I. G.; Clemente-Colon, P.; Freeman, A.; Richter, A.; Burrows, J. P.; Shepson, P. B.; Bottenheim, J. W.; Barber, D. G.; Simpson, W. R.; Perovich, D. K.; Sturm, M.; Steffen, A.; Kaleschke, L.; Hall, D. K.; Markus, T.; Eicken, H.; Neumann, G.

2010-12-01

290

Spin-orbit interactions in vortex singularimetry  

NASA Astrophysics Data System (ADS)

On scattering, the high strength singularity of a vortex beam breaks into a configuration of single charge vortices. The precise geometry of such a vortex constellation depends on the angle of incidence and the material properties of the scatterer, but also on the optical spin-orbit coupling as choosing different input and output polarization results in a family of vortex constellation. Measuring the position of the individual vortices allows us to reconstruct elements in an systematic expansion of the scattering matrix, in an analogy to optical aberration theory. We discuss in detail the dependence of the constellation geometry on external parameters, which is the basis for an optical metrology based on vortices.

Götte, Jörg B.; Dennis, Mark R.

2013-09-01

291

Regional stratospheric warmings in the Pacific-Western Canada (PWC) sector during winter 2004/2005: implications for temperatures, winds, chemical constituents and the characterization of the Polar vortex  

NASA Astrophysics Data System (ADS)

The vortex during winter 2004/2005 was interesting for several reasons. It has been described as "cold" stratospherically, with relatively strong westerly winds. Losses of ozone until the final warming in March were considerable, and comparable to the cold 1999 2000 winter. There were also modest warming events, indicated by peaks in 10 hPa zonal mean temperatures at high latitudes, near 1 January and 1 February. Events associated with a significant regional stratospheric warming in the Pacific-Western Canada (PWC) sector then began and peaked toward the end of February, providing strong longitudinal variations in dynamical characteristics (Chshyolkova et al., 2007; hereafter C07). The associated disturbed vortex of 25 February was displaced from the pole and either elongated (upper) or split into two cyclonic centres (lower). Observations from Microwave Limb Sounder (MLS) on Aura are used here to study the thermal characteristics of the stratosphere in the Canadian-US (253° E) and Scandinavian-Europe (16° E) sectors. Undisturbed high latitude stratopause (55 km) zonal mean temperatures during the mid-winter (December February) reached 270 K, warmer than empirical-models such as CIRA-86, suggesting that seasonal polar warming due to dynamical influences affects the high altitude stratosphere as well as the mesosphere. There were also significant stratopause differences between Scandinavia and Canada during the warming events of 1 January and 1 February, with higher temperatures near 275 K at 16° E. During the 25 February "PWC" event a warming occurred at low and middle stratospheric heights (10 30 km: 220 K at 253° E) and the stratopause cooled; while over Scandinavia-Europe the stratosphere below ~30 km was relatively cold at 195 K and the stratopause became even warmer (>295 K) and lower (~45 km). The zonal winds followed the associated temperature gradients so that the vertical and latitudinal gradients of the winds differed strongly between Scandinavia-Europe and Canada-US. The data-archive of Aura-MLS was also used to produce height versus latitude contours of ozone and related constituents, using mixing ratios (r) for ClO, N2O and HCl, for the 16° E and 253° E sectors. The Q-diagnostic was used to display the positions of the cyclonic (polar) vortex, using data from the UK Meteorological Office (MetO) analyses. ClO/HCL maxima/minima occurred on 1 February in both sectors, consistent with loss of ozone by heterogeneous chemistry. Low N2O values at high latitudes indicated that both sectors were inside the polar vortex, Time-difference plots show greater reductions in O3 in the Canadian sector. For the 25 February PWC warming event, O3-rich air from lower latitudes continued to be excluded from Europe, while O3 penetrated to at least 82° N over the Canadian sector. The contours for ClO, N2O and HCl at 16° E are consistent with continued ozone loss within the vortex during the event. Finally the thermal and chemical changes at these 16° E and 253° E sectors are placed into a hemispheric context using polar-cylindrical plots, with the following results. Firstly, the mixing ratios of O3, ClO, HNO3, HCL and the temperatures from Aura-MLS were consistent with consensus views of heterogeneous chemistry. Secondly, and consistent with the polar plots of C07, the vortices and their edges were strongly distorted during the 1 January, 1 and 25 February warming events, with sinusoidal shapes consistent with stationary planetary waves of wave-numbers 1 and 2. Thirdly, the distributions of the chemicals followed the curvatures (cyclonic and anticyclonic) of the vortex edges with O3 losses occurring at the cold cyclonic locations. During February these were over Scandinavia-Western Europe and Central-Eastern Canada. Trajectory analysis was applied to the two February warming events. For the 1 February event, the rotation time for air parcels within the peanut-shaped vortex was 3 4 days; while the O3-rich low latitude air that entered the Pacific-Western Canada sector during the 25 February event, s

Manson, A. H.; Meek, C. E.; Chshyolkova, T.

2008-11-01

292

From the Bottom to the Stratosphere Arctic Climate Features as Seen from the First International Polar Year (1882–1883) Until the End of World War II  

Microsoft Academic Search

After the establishment of national weather services and the development of early weather forecasts towards the end of the\\u000a 19th century, the Arctic region was seen as the home of cyclones, which very often resulted in violent storms in northern\\u000a latitudes and influenced the weather of middle latitudes. Between 1882 and 1945 Arctic climate features were observed starting\\u000a from ground-based

C. Lüdecke

293

Dynamics of vortex nucleation in nanomagnets with broken symmetry  

NASA Astrophysics Data System (ADS)

We investigate the dynamics of magnetic vortex nucleation in sub-100-nm mesoscopic magnets with the aim of establishing an independent control of vortex polarity and chirality. We consider the dynamic behavior of the vortex spin structure in an object with broken symmetry—a Pacman-like nanomagnet shape—proposing a model based on classical electrodynamics and providing a proof by conducting micromagnetic calculations. The model provides evidence that the desired vortex chirality and polarity could be established by applying solely quasistatic in-plane magnetic field along specific directions with respect to the structure's asymmetry. We identify the modes of vortex nucleation that are robust against external magnetic field noise. These vortex nucleation modes are common among a wide range of sub-100-nm magnets with broken rotational symmetry. The results could lead to the practical realization of high density magnetic memories based on magnetic vortices.

Tóbik, Jaroslav; Cambel, Vladimír; Karapetrov, Goran

2012-10-01

294

Estimation of Arctic polar vortex ozone loss during the winter of 1999-2000 using vortex-averaged airborne differential absorption lidar ozone measurements referenced to N2O isopleths  

Microsoft Academic Search

The NASA Langley UV differential absorption lidar (DIAL) system flew on the NASA DC-8 aircraft during the Stratospheric Aerosol and Gas Experiment (SAGE) III Ozone Loss and Validation Experiment\\/Third European Stratospheric Experiment on Ozone 2000 (SOLVE\\/THESEO 2000) mission from 30 November 1999 to 15 March 2000. The UV DIAL system measured ozone (O3) profiles at altitudes from about 1 km

William B. Grant; Edward V. Browell; Carolyn F. Butler; Sharon C. Gibson; Susan A. Kooi; Peter von der Gathen

2003-01-01

295

Super Interglacials and persistent warmth paced Arctic Climate Evolution over the Past 3.6 Myr: Lake El'gygytgyn, Western Beringia, a new polar lens focused on high latitude environmental change  

NASA Astrophysics Data System (ADS)

The Pliocene-Pleistocene climate evolution of the Arctic must have modulated the glacial history of Greenland and the onset of Northern Hemisphere glaciation. Yet what is known from the terrestrial stratigraphy of Arctic climate change comes from sites that are spatially and temporally fragmented. In 2009, International Continental Deep drilling at Lake El'gygytgyn (67o30' N, 172 o 05' E) recovered lacustrine sediments dating back to 3.58 Ma that now provide the first time-continuous Pliocene-Pleistocene Arctic paleoclimate record of alternating glacial-interglacial change. The warmest/wettest Pliocene interval of the lake record occurs from ~3.58-3.34 Ma and is dominated by exceptional tree pollen implying July temperatures nearly 7-8o C warmer than today with nearly ~3 times the annual precipitation. Atmospheric CO2 levels are estimated to have been 360 to 400 ppm implying exceptionally high climate sensitivity and polar amplification. In fact, pollen spectra and modern analog analysis show an unbroken persistence of summers much warmer and wetter than the last interglacial, MIS 5e until nearly 2.2 Ma. Extreme warmth in the Mid Pliocene Arctic occurs at the same time ANDRILL results suggest the West Antarctic Ice Sheet was non-existent. Modeling sensitivity experiments using 300 and 400 ppm CO2 are consistent with sustained forests at Lake El'gygytgyn during this interval and restricted glacial ice over Greenland in both cold and warm boreal summer orbits especially for the PRISM interval. This has implications for reinterpreting the M2 isotopic shift in the North Atlantic suggesting that most of the ice advance at that time was in Antarctica. Using physical, chemical, and biological proxies we find pronounced glacial episodes commenced ~2.6 Ma ago, but the full range of typical Pleistocene glacial/interglacial change wasn't established until ~1.8 Ma ago. Greenland must have also responded to numerous "super interglacials" during the Quaternary record, with maximum summer temperatures and annual precipitation, especially during MIS 9,11 and 31, at Lake El'gygytgyn exceeding that documented for MIS 5e. The correspondence of many of these super-interglacials with retreat of the West Antarctic Ice Sheet (Naish et al. 2009) could coincide with intervals when the Greenland Ice was reduced in size. The climate record from Lake El'gygytgyn, especially the history of past interglacials, provides a fresh means of testing the evolving magnitude of polar amplification over time, and the sensitivity of the Greenland Ice Sheet to extreme warmth in the rest of the Arctic.

Brigham-Grette, Julie; Melles, Martin; Minyuk, Pavel

2013-04-01

296

Arctic hydroclimatology  

Microsoft Academic Search

Arctic air temperature, precipitation, ground temperature, river runoff, clouds, and radiation are all changing quickly in a warming climate. Interactions and feedbacks between these features are not well understood. In particular, the relative role of local climate processes and large-scale ocean-atmosphere dynamics in driving observed Arctic changes is difficult to ascertain because of the sparsity of observations, inaccuracy of those

Jessica Ellen Cherry

2007-01-01

297

Record-breaking Ozone Loss during Arctic Winter 2010/2011: Comparison with Arctic Winter 1996/1997  

NASA Astrophysics Data System (ADS)

Polar processing and chemical ozone loss is analysed during the Arctic winter/spring 2010/2011. The analyses with temperatures and potential vorticity (PV) data show a prolonged vortex from early December through mid-April. The PV maps illustrate strong vortex persistence in the lower stratosphere between 450 and 675 K, showing similar evolution with time. The minimum temperatures extracted from ECMWF data at 40-90°N show values below 195 K for a record period of first week of December through second week of April, indicating the longest period of colder temperatures for 17 years. At 10 hPa, there was a warming of about 10 K at 60°N and 40 K at 90°N around mid-January. The heat flux also showed high values in line with the increase in temperatures, of about 425 m K/s at 60°N at the same pressure level. However, the westerlies were strong (e.g. 35-45 m/s at 60°N) enough to keep the vortex intact until mid-April. Because of the cold temperatures in late winter and early spring, large areas of Polar Stratospheric Clouds (PSC) were found in the 400-600 K isentropic level range. Though the maximum values of PSCs area are smaller compared to other cold winters such as 2005, the extended period of presence of PSCs during this winter was exceptional, especially in late February-mid-March, in agreement with the cold temperatures during the period. Ozone loss analyses with high resolution Mimosa-Chim chemical transport model simulations show that the loss started by early January, and was about 0.5 ppmv in late January. The loss progressed slowly to 1 ppmv by the end of February, and then intensified by early March. The ozone depletion estimated by the passive method finds a maximum value of about 2-2.3 ppmv by the end of March-early April in the 450-550K range inside the vortex, which coincides with the areas of PSCs and high chlorine activation. This is the largest loss ever estimated with this model for any Arctic winter. It is consistent with the unprecedented chlorine activation that occurred in the winter, as the modeled ClO values show about 1.7 ppbv in early January and about 1 ppbv in March at 450-550K. This is longest period of chlorine activation noted among the Arctic winters. The ozone partial column loss reaches about 115-150 DU in the range 350 - 550 K. These model results for ozone, ozone loss and ClO are in good agreement with those found from Aura Microwave Limb Sounder observations. Since the winter 1996/1997 was also very cold in March - April, a comparison between both winters 2011 and 1997 will be presented, based on temperature, PV, Heat flux data and ozone loss estimations. Similarities and differences in the polar processing and ozone loss during both winters will be discussed using various measurements and model simulations. Copyright 2011. All rights reserved.

Godin Beekmann, S.; Kuttipurath, J.; Lefèvre, F.; Santee, M. L.; Froidevaux, L.

2011-12-01

298

Control of the chirality and polarity of magnetic vortices in triangular nanodots  

Microsoft Academic Search

Magnetic vortex dynamics in lithographically prepared nanodots is currently a subject of intensive research, particularly after recent demonstration that the vortex polarity can be controlled by in-plane magnetic field. This has stimulated the proposals of nonvolatile vortex magnetic random access memories. In this work, we demonstrate that triangular nanodots offer a real alternative where vortex chirality, in addition to polarity,

M. Jaafar; R. Yanes; D. Perez de Lara; O. Chubykalo-Fesenko; A. Asenjo; E. M. Gonzalez; J. V. Anguita; M. Vazquez; J. L. Vicent

2010-01-01

299

Airborne arctic stratospheric expedition II: An overview  

SciTech Connect

The sudden onset of ozone depletion in the antarctic vortex set a precedent for both the time scale and the severity of global change. The Airborne Antarctic Ozone Experiment (AAOE), staged from Punta Arenas, Chile, in 1987, established that CFCs, halons, and methyl bromide, the dominant sources of chlorine and bromine radicals in the stratosphere, control the rate of ozone destruction over the Antarctic; that the vortex is depleted in reactive nitrogen and water vapor; and that diabatic cooling during the antarctic winter leads to subsidence within the vortex core, importing air from higher altitudes and lower latitudes. This last conclusion is based on observed dramatic distortion in the tracer fields, most notably N[sub 2]O. In 1989, the first Airborne Arctic Stratospheric Expedition (AASE-I), staged from Stavanger, Norway, and using the same aircraft employed for AAOE (the NASA ER-2 and the NASA DC-8), discovered that while NO[sub x] and to some degree NO[sub y] were perturbed within the arctic vortex, there was little evidence for desiccation. Under these (in contrast to the antarctic) marginally perturbed conditions, however, ClO was found to be dramatically enhanced such that a large fraction of the available (inorganic) chlorine resided in the form of ClO and its dimer ClOOCl. This leaves two abiding issues for the northern hemisphere and the mission of the second Airborne Arctic Stratospheric Expedition (AASE-II): (1) Will significant ozone erosion occur within the arctic vortex in the next ten years as chlorine loading in the stratosphere exceeds four parts per billion by volume (2) Which mechanisms are responsible for the observed ozone erosion poleward of 30[degrees]N in the winter/spring northern hemisphere reported in satellite observations 12 refs., 2 tabs.

Anderson, J.G. (Harvard Univ., Cambridge, MA (United States)); Toon, O.B. (NASA Ames Research Center, Moffett Field, CA (United States))

1993-11-19

300

Dietary correlates of an at-risk BMI among Inuit adults in the Canadian high arctic: cross-sectional international polar year Inuit health survey, 2007-2008  

PubMed Central

Background The study’s objective was to investigate the dietary correlates of an at-risk body mass index (BMI) among Inuit adults from thirty-six communities across the Canadian Arctic using data from the cross-sectional International Polar Year Inuit Health Survey, conducted in 2007–2008. Methods The survey included assessments of 24-hr dietary recall, sociodemographics, physical activity, and anthropometry. Dietary characteristics of overweight and obesity were similar and therefore combined into one at- risk BMI category (?25?kg/m2) for analyses. The relationship between an at-risk BMI and energy intake from macronutrients, high sugar drinks, high-fat foods, saturated fatty acids, and traditional foods were examined entering each dietary variable separately into a logistic regression model as an independent variable. Analyses were adjusted for age, sex, region, kcalories, walking, smoking and alcohol consumption. Further multivariable models considered selected dietary variables together in one model. Results An at-risk BMI was present for 64% with a prevalence of overweight and obesity of 28% and 36%, respectively. Consumption of high-sugar drinks (>15.5% E) was significantly related with having an at-risk BMI (OR?=?1.6; 95% CI 1.2; 2.2), whereas the % E from total carbohydrate evaluated as a continuous variable and as quartiles was inversely related to an at-risk BMI (P?-trend

2012-01-01

301

A three-dimensional characterization of Arctic aerosols from airborne Sun photometer observations: PAM-ARCMIP, April 2009  

NASA Astrophysics Data System (ADS)

The Arctic climate is modulated, in part, by atmospheric aerosols that affect the distribution of radiant energy passing through the atmosphere. Aerosols affect the surface-atmosphere radiation balance directly through interactions with solar and terrestrial radiation and indirectly through interactions with cloud particles. Better quantification of the radiative forcing by different types of aerosol is needed to improve predictions of future climate. During April 2009, the airborne campaign Pan-Arctic Measurements and Arctic Regional Climate Model Inter-comparison Project (PAM-ARCMIP) was conducted. The mission was organized by Alfred Wegener Institute for Polar and Marine Research of Germany and utilized their research aircraft, Polar-5. The goal was to obtain a snapshot of surface and atmospheric conditions over the central Arctic prior to the onset of the melt season. Characterizing aerosols was one objective of the campaign. Standard Sun photometric procedures were adopted to quantify aerosol optical depth AOD, providing a three-dimensional view of the aerosol, which was primarily haze from anthropogenic sources. Independent, in situ measurements of particle size distribution and light extinction, derived from airborne lidar, are used to corroborate inferences made using the AOD results. During April 2009, from the European to the Alaskan Arctic, from sub-Arctic latitudes to near the pole, the atmosphere was variably hazy with total column AOD at 500 nm ranging from ˜0.12 to >0.35, values that are anomalously high compared with previous years. The haze, transported primarily from Eurasian industrial regions, was concentrated within and just above the surface-based temperature inversion layer. Extinction, as measured using an onboard lidar system, was also greatest at low levels, where particles tended to be slightly larger than at upper levels. Black carbon (BC) (soot) was observed at all levels sampled, but at moderate to low concentrations compared with historical records. BC was highest near the North Pole, suggesting there had been an accumulation of soot within the Arctic vortex. Few, optically thick elevated aerosol layers were observed along the flight track, although independent lidar observations reveal evidence of the passage of volcanic plumes, which may have contributed to abnormally high values of AOD above 4 km. Enhanced opacity at higher altitudes during the campaign is attributed to an accumulation of industrial pollutants in the upper troposphere in combination with volcanic aerosol resulting from the March-April 2009 eruptions of Mount Redoubt in Alaska. The presence of Arctic haze during April 2009 is estimated to have reduced the net shortwave irradiance by ˜2-5 W m-2, resulting in a slight cooling of the surface.

Stone, R. S.; Herber, A.; Vitale, V.; Mazzola, M.; Lupi, A.; Schnell, R. C.; Dutton, E. G.; Liu, P. S. K.; Li, S.-M.; Dethloff, K.; Lampert, A.; Ritter, C.; Stock, M.; Neuber, R.; Maturilli, M.

2010-07-01

302

Vortex Flow Aerodynamics, volume 1  

SciTech Connect

Vortex modeling techniques and experimental studies of research configurations utilizing vortex flows are discussed. Also discussed are vortex flap investigations using generic and airplane research models and vortex flap theoretical analysis and design studies.

Campbell, J.F.; Osborn, R.F.; Foughner, J.T. Jr.

1986-07-01

303

Magnetic vortex dynamics induced by spin-transfer torque  

NASA Astrophysics Data System (ADS)

We theoretically study the dynamics of a magnetic vortex under spin-polarized electric current in ferromagnets. The equation of motion of the vortex in terms of collective coordinates is derived. We compare our theory with recent experiments for current-induced vortex displacement and resonance motion in a ferromagnetic nanodot. Our estimate for the displacement and the resonance frequency shows a good agreement with the experiment. We also study the current-induced motion of a vortex wall in a ferromagnetic thin wire.

Shibata, J.; Nakatani, Y.; Tatara, G.; Kohno, H.; Otani, Y.

2007-03-01

304

Analysis of the spatial distribution of the unusual NO2 enhancements in the Arctic polar upper stratosphere and mesosphere observed by GOMOS-Envisat in January-March 2004  

NASA Astrophysics Data System (ADS)

Anomalously enhanced NO2 concentrations are sometimes observed in the polar winter upper atmosphere. The enhancements over Antarctica from May to August 2003 were probably due to auroral electron precipitation, producing high amounts of NO in the upper mesosphere that were converted to NO2 during downward transport to the stratosphere. Another enhancement was detected in the Arctic middle stratosphere in October-November 2003, due this time to energetic solar proton precipitation. This enhancement was quickly followed by a new Arctic NO2 enhancement produced by auroral electrons in November 2003. Finally, a last enhancement was detected in the lower mesosphere from January to April 2004. Although it was proposed that this enhancement could also be due to auroral electrons, uncertainties remained concerning the absolute value of the NO2 enhancement and its spatial coverage. We propose here a new analysis of the Global Ozone Monitoring by Occultation of Stars (GOMOS) nighttime measurements of the NO2 enhancements. Instead of using daily zonally averaged data as done previously, we consider only the profiles containing the maximum values of the NO2 enhancement. Unlike all the previous enhancements, the NO2 content of the January 2004 appears to be longitudinally and latitudinally dependent inside the polar circle. The enhancement starts on 17 January 2004, with mixing ratios of up to a ppmv at altitudes above 60 km on 21 January. The enhancement looks like a “hot spot” above the polar cap. Then the enhancement spreads while it propagates downward into the stratosphere. It is accompanied by perfectly coincident strong ozone depletion; in particular, ozone is almost totally destroyed in mid-February at about 50 km. The vertical extent and horizontal spread of this NO2 enhancement strongly differ from the November 2003 enhancement attributed to auroral electron precipitation. The possible origins of this unusual pattern are discussed.

Renard, Jean-Baptiste; Bekki, Slimane; Blelly, Pierre-Louis; Bourgeois, Quentin; Berthet, Gwenaël; Hauchecorne, Alain

2009-12-01

305

Summer at-sea distribution of seabirds and marine mammals in polar ecosystems: a comparison between the European Arctic seas and the Weddell Sea, Antarctica  

Microsoft Academic Search

The summer at-sea distribution of seabirds and marine mammals was quantitatively established both in Antarctica (Weddell Sea) and in the European Arctic: Greenland, Norwegian and Barents seas. Data can directly be compared, since the same transect counts were applied by the same team from the same icebreaking ship in both regions. The main conclusion is that densities of seabirds and

Claude R Joiris

2000-01-01

306

Wingtip Vortex Propeller.  

National Technical Information Service (NTIS)

A device which increases the energy efficiency and aerodynamic properties of aircraft was developed. A wingtip pusher propeller is positioned aft of the wingtip to rotate in the crossflow of the wingtip vortex. The propeller rotates against the vortex swi...

J. C. Patterson

1984-01-01

307

Arctic contamination poses potential danger  

NASA Astrophysics Data System (ADS)

Following the dissolution of the former Soviet Union, some studies have been focused on the impact of radioactive and hazardous materials released into the Arctic environment, including air, water, and ground. Contamination from radionuclides, trace metals, and hydrocarbons has been examined. Speaking at the 73rd meeting of the National Research Council's Polar Research Board held June 28 in Washington, D.C., Lou Codispoti, Office of Naval Research, said that scientists have found that there is no immediate regional concern relating to this contamination, although the potential for future concern exists.Bruce Molnia, chief of polar programs at the U.S. Geological Survey, reported on a workshop on Arctic contamination that was held in Anchorage, Alaska, from May 2-7. The workshop was organized by the U.S. Interagency Arctic Research Policy Committee (IARPC), which is made up of fourteen federal agencies that conduct research in the Arctic, in response to Frank Murkowski (R-Alaska) asking what federal agencies would do about contamination in the Arctic. IARPC developed an “agenda for action,” which included the Anchorage workshop.

Bush, Susan

308

Arctic energy technologies workshop: proceedings  

SciTech Connect

The objectives of this ''Arctic Energy Technologies Workshop'' were threefold: To acquaint participants with the current US Department of Energy, Office of Fossil Energy, Arctic and Offshore Research Program. To obtain information on Arctic oil and gas development problem areas, and on current and planned research. To provide an opportunity for technical information exchange among engineers, geologists, geophysicists, physical scientists, oceanographers, statisticians, analysts, and other participants engaged in similar research areas. The first section of the proceedings is the keynote address ''Current Arctic Offshore Technology'', presented by Kenneth Croasdale, of K.R. Croasdale and Associates, Ltd., Calgary, Alberta, Canada. The second section of the proceedings includes 14 technical papers presented in two sessions at the Workshop: Sea Ice Research, and Seafloor/Soils Research. The third section of the proceedings includes the summaries of four work-group discussion sessions from the second day of the meeting: (1) Arctic Offshore Structures, (2) Arctic Offshore Pipelines, (3) Subice Development Systems, and (4) Polar-Capable Ice Vessels. The work groups addressed state-of-the-art, technical issues, R and D needs, and environmental concerns in these four areas. All papers in this proceedings have been processed for inclusion in the Energy Data Base.

Not Available

1985-04-01

309

The Swirling Vortex  

Microsoft Academic Search

We consider an infinite vortex line in a viscous fluid interacting with a plane boundary surface at right angles to the line. If the boundary surface were absent, the vortex would impart to the fluid a circular motion about the vortex line with speed inversely proportional to the distance to the line. The presence of the boundary surface, however, leads

J. Serrin

1972-01-01

310

Beyond Penguins and Polar Bears: Polar Geography  

NSDL National Science Digital Library

Our presenters provide an overview of the geography of the Arctic and Antarctic regions and featured resources from the Beyond Penguins and Polar Bears cyberzine, a resource for elementary educators. This cyberzine focuses on strategies and content to integrate science and literacy through the study of the polar regions. Recorded on May 27, 2008, Beyond Penguins and Polar Bears: Integrating Science and Literacy, Seminar 1: Polar Geography, NSDL featured our experts from The Ohio State University, Jessica Fries-Gaither, Project Director for Beyond Penguins and Polar Bears and Elementary Resource Specialist at the Ohio Resource Center and Dr. Carol Landis, Education Coordinator at the Byrd Polar Research Center.

Payo, Robert

311

Modeling the Frozen-In Anticyclone in the 2005 Arctic Summer Stratosphere  

NASA Astrophysics Data System (ADS)

Immediately following the breakup of the 2005 Arctic spring stratospheric vortex, a tropical air mass, characterized by low potential vorticity (PV) and high nitrous oxide (N2O), was advected poleward and became trapped in the easterly summer polar vortex. This feature, known as a "Frozen-In Anticyclone (FrIAC)", was observed in Earth Observing System (EOS) Aura Microwave Limb Sounder (MLS) data to span the potential temperature range from ~580 to 1100 K (~25 to 40 km altitude) and to persist from late March to late August 2005. This study compares MLS N2O observations with simulations from the Global Modeling Initiative (GMI) chemistry and transport model, the GEOS-5/MERRA Replay model, and the Van Leer Icosahedral Triangular Advection (VITA) isentropic transport model to elucidate the processes involved in the lifecycle of the FrIAC, which is here divided into three distinct phases. During the "spin-up phase" (March to early April), strong poleward flow resulted in a tight isolated anticyclonic vortex at ~70-90° N, marked with elevated N2O. GMI, Replay, and VITA all reliably simulated the spin-up of the FrIAC, although the GMI and Replay peak N2O values were too low. The FrIAC became trapped in the developing summer easterly flow and circulated around the polar region during the "anticyclonic phase" (early April to the end of May). During this phase, the FrIAC crossed directly over the pole between 7 and 14 April. The VITA and Replay simulations transported the N2O anomaly intact during this crossing, in agreement with MLS, but unrealistic dispersion of the anomaly occurred in the GMI simulation due to excessive numerical mixing of the polar cap. The vortex associated with the FrIAC was apparently resistant to the weak vertical shear during the anticyclonic phase, and it thereby protected the embedded N2O anomaly from stretching. The vortex decayed in late May due to diabatic processes, leaving the N2O anomaly exposed to horizontal and vertical wind shears during the "shearing phase" (June to August). The observed lifetime of the FrIAC during this phase is consistent with timescales calculated from the ambient horizontal and vertical wind shear. Replay maintained the horizontal structure of the N2O anomaly similar to MLS well into August. Isentropic simulations using VITA also captured the horizontal structure of the FrIAC during this phase, but small-scale structures maintained by VITA are problematic and show that important mixing processes are absent from this single-level simulation.

Allen, D. R.; Douglass, A. R.; Manney, G. L.; Strahan, S. E.; Krosschell, J. C.; Trueblood, J. V.; Nielsen, J. E.; Pawson, S.; Zhu, Z.

2011-05-01

312

Modeling the Frozen-In Anticyclone in the 2005 Arctic summer stratosphere  

NASA Astrophysics Data System (ADS)

Immediately following the breakup of the 2005 Arctic spring stratospheric vortex, a tropical air mass, characterized by low potential vorticity (PV) and high nitrous oxide (N2O), was advected poleward and became trapped in the easterly summer polar vortex. This feature, known as a "Frozen-In Anticyclone (FrIAC)", was observed in Earth Observing System (EOS) Aura Microwave Limb Sounder (MLS) data to span the potential temperature range from ~580 to 1100 K (~25 to 40 km altitude) and to persist from late March to late August 2005. This study compares MLS N2O observations with simulations from the Global Modeling Initiative (GMI) chemistry and transport model, the GEOS-5/MERRA Replay model, and the Van Leer Icosahedral Triangular Advection (VITA) isentropic transport model to elucidate the processes involved in the lifecycle of the FrIAC, which is here divided into three distinct phases. During the "spin-up phase" (March to early April), strong poleward flow resulted in a tight isolated anticyclonic vortex at ~70-90° N, marked with elevated N2O. GMI, Replay, and VITA all reliably simulated the spin-up of the FrIAC, although the GMI and Replay peak N2O values were too low. The FrIAC became trapped in the developing summer easterly flow and circulated around the polar region during the "anticyclonic phase" (early April to the end of May). During this phase, the FrIAC crossed directly over the pole between the 7 and 14 April. The VITA and Replay simulations transported the N2O anomaly intact during this crossing, in agreement with MLS, but unrealistic dispersion of the anomaly occurred in the GMI simulation due to excessive numerical mixing of the polar cap. The vortex associated with the FrIAC was apparently resistant to the weak vertical shear during the anticyclonic phase, and it thereby protected the embedded N2O anomaly from stretching. The vortex decayed in late May due to diabatic processes, leaving the N2O anomaly exposed to horizontal and vertical wind shears during the "shearing phase" (June to August). The observed lifetime of the FrIAC during this phase is consistent with timescales calculated from the ambient horizontal and vertical wind shear. Replay maintained the horizontal structure of the N2O anomaly similar to MLS well into August. The VITA simulation also captured the horizontal structure of the FrIAC during this phase, but VITA eventually developed fine-scale N2O structure not observed in MLS data.

Allen, D. R.; Douglass, A. R.; Manney, G. L.; Strahan, S. E.; Krosschell, J. C.; Trueblood, J. V.; Nielsen, J. E.; Pawson, S.; Zhu, Z.

2011-02-01

313

Evidence of vortex jamming in Abrikosov vortex flux flow regime  

NASA Astrophysics Data System (ADS)

We report on dynamics of nonlocal Abrikosov vortex flow in mesoscopic superconducting Nb channels. Magnetic field dependence of the nonlocal voltage induced by the flux flow shows that vortices form ordered vortex chains. Voltage asymmetry (rectification) with respect to the direction of vortex flow is evidence that vortex jamming strongly moderates vortex dynamics in mesoscopic geometries. The findings can be applied to superconducting devices exploiting vortex dynamics and vortex manipulation, including superconducting wires with engineered pinning centers.

Karapetrov, G.; Yefremenko, V.; Mihajlovi?, G.; Pearson, J. E.; Iavarone, M.; Novosad, V.; Bader, S. D.

2012-08-01

314

Evidence of Vortex Jamming in Abrikosov Vortex Flux Flow Regime  

NASA Astrophysics Data System (ADS)

We report on dynamics of non-local Abrikosov vortex flow in mesoscopic superconducting Nb channels. Magnetic field dependence of the non-local voltage induced by the flux flow shows that vortices form ordered vortex chains. Voltage asymmetry (rectification) with respect to the direction of vortex flow is evidence that vortex jamming strongly moderates vortex dynamics in mesoscopic geometries. The findings can be applied to superconducting devices exploiting vortex dynamics and vortex manipulation, including superconducting wires with engineered pinning centers.

Karapetrov, Goran; Yefremenko, V.; Mihajlovic, G.; Pearson, J. E.; Iavarone, M.; Novosad, V.; Bader, S. D.

2012-02-01

315

Variations and climatology of ClO in the polar lower stratosphere from UARS Microwave Limb Sounder measurements  

NASA Astrophysics Data System (ADS)

The Microwave Limb Sounder (MLS) on board the Upper Atmosphere Research Satellite (UARS) measured the global distribution of stratospheric ClO over annual cycles for much of the 1990s, albeit with reduced sampling frequency in the latter half of the decade. Here we present an overview of the interannual and interhemispheric variations in the distribution of ClO derived from UARS MLS measurements, with a particular emphasis on enhancements in the winter polar lower stratosphere. Although ClO enhancement within the Arctic vortex is comparable in both magnitude and spatial extent to that in the Antarctic at 465 K (˜19 km), a significant interhemispheric disparity is seen at higher altitudes, where maximum ClO abundances, and their spatial extent, are considerably larger in the Antarctic than in the Arctic. The Arctic exhibits much more interannual variability in the magnitude, timing, and distribution of ClO enhancement than does the Antarctic. Nevertheless, during the mid-1990s, when the Arctic lower stratosphere was atypically cold, MLS observed the Arctic vortex to be almost completely filled with enhanced ClO in midwinter to late winter. The peak in the ClO profile is at a higher altitude, and the vertical extent of chlorine activation is larger, in the Antarctic than in the Arctic. The Arctic winter of 1995/1996, however, stands out as having a much more Antarctic-like ClO distribution, with larger maximum ClO abundances, a higher altitude for the profile peak, and greater horizontal and vertical extent of activation than the other winters observed by UARS MLS. In the Southern Hemisphere, ClO becomes enhanced in the sunlit portions of the vortex by at least late May/early June every year, whereas in the Northern Hemisphere, ClO becomes enhanced in mid to late December in some years but not until January in others. Elevated levels of reactive chlorine persist for 4-5 months in the south but only 2-3 months in the north.

Santee, M. L.; Manney, G. L.; Waters, J. W.; Livesey, N. J.

2003-08-01

316

A study of ozone depletion in the 2004/2005 Arctic winter based on data from Odin/SMR and Aura/MLS  

NASA Astrophysics Data System (ADS)

Ozone depletion in the colder than average 2004/2005 Arctic polar vortex is mapped and quantified using ozone profiles from two limb sounding satellite instruments, the Earth Observing System Microwave Limb Sounder (Aura/MLS) and the Odin Sub-Millimetre Radiometer (Odin/SMR). Profiles of chemically inert nitrous oxide (N2O) are used to trace vertical transport during the winter. Two methods are used for estimating the vortex average ozone losses north of 67° equivalent latitude. In a first step, the time evolution of ozone mixing ratios is described on N2O isopleths. Maximum ozone depletion is found on the 100 ppbv and 150 ppbv N2O isopleths (located in the 430-460 K potential temperature range in mid-March 2005) where vortex average ozone depletion totalled 1.0-1.1 ppmv for Aura/MLS and 0.7-0.9 ppmv for Odin/SMR. Second, ozone profiles from Aura/MLS and Odin/SMR are assimilated into the DIAMOND isentropic transport model. Ozone depletion is estimated by comparing assimilated fields to ozone fields passively transported from 1 January. On the 450 K potential temperature level, the Aura/MLS ozone fields indicate 0.9-1.3 ppmv vortex-averaged ozone depletion while the Odin/SMR fields indicate 0.6-0.9 ppmv depletion. The uncertainty depends mainly on the rates of cross-isentropic transport used in the study. The ozone depletion estimates in this study are lower than previously published estimates. The discrepancies to some studies can be attributed to the more adequate treatment of an ozone poor region that is found in the central polar vortex in the early winter.

RöSevall, J. D.; Murtagh, D. P.; Urban, J.; Feng, W.; Eriksson, P.; Brohede, S.

2008-07-01

317

Polarization of 'water-skies' above arctic open waters: how polynyas in the ice-cover can be visually detected from a distance  

Microsoft Academic Search

The foggy sky above a white ice-cover and a dark water surface (permanent polynya or temporary lead) is white and dark gray, phenomena called the 'ice-sky' and the 'water-sky,' respectively. Captains of icebreaker ships used to search for not-directly-visible open waters remotely on the basis of the water sky. Animals depending on open waters in the Arctic region may also

Ramón Hegedüs; Susanne Åkesson; Gábor Horváth

2007-01-01

318

Global impacts of Arctic climate processes  

Microsoft Academic Search

The polar regions are experiencing major climate and environmental changes due to the combined effects of natural variability and global warming. To address regional Arctic climate processes and their global feedbacks, 53 experts from the United States, Canada, Europe, and Russia gathered for a recent workshop at the Alfred Wegener Institute for Polar and Marine Research, in Potsdam, Germany.The workshop,

Klaus Dethloff; Annette Rinke; Hugh Morrison; Wolfgang Dorn; Ruediger Gerdes; Wieslaw Maslowski; Vladimir Kattsov; Manfred A. Lange; Klaus Görgen; Amanda Lynch

2005-01-01

319

Arctic National Wildlife Refuge  

NSDL National Science Digital Library

This is the homepage of the Arctic National Wildlife Refuge (ANWR). Materials available here include information for visitors, refuge history and culture, information on the refuge's oil and gas resources. There is also extensive information on wild lands and wildlife, including caribou, bears, moose, wolves, and muskoxen, among others. Caribou calving maps, caribou movements, polar bear and muskox locations, snow geese fall use areas, and fish locations are available on maps. Habitat details are described, including a section on ice wedges and other permafrost features.

320

Arctic UTLS composition measured by the MARSCHALS instrument during the PREMIEREX and ESSENCE campaigns  

NASA Astrophysics Data System (ADS)

An overview of the results obtained by the MARSCHALS (Millimetre-wave Airborne Receivers for Spectroscopic CHaracterisation in Atmospheric Limb Sounding) instrument during Premier-Ex (March 2010, Kiruna, Sweden) and ESSenCe 2011 (December 2011, Kiruna, Sweden) aircraft Arctic campaigns is presented. The two campaigns were part of the activities conducted as preparatory studies for PREMIER (Process Exploration through Measurements of Infrared and millimeter-wave Emitted Radiation), one of the three candidate core missions of ESA Earth Explorer 7. The primary objective of PREMIER is to gain a better understanding of the processes that are linking atmospheric chemistry and dynamics with climate. PREMIER will achieve this by observing the Upper Troposphere / Lower Stratosphere (UTLS) - a region of particular importance in the study of climate change - with unprecedented spatial and temporal resolution. PREMIER combines the complementary capabilities of two limb-sounders in the infrared and millimeter-wave spectral regions and MARSCHALS was developed as an airborne demonstrator of the PREMIER millimeter-wave spectrometer. In the frame of the two Arctic campaigns, MARSCHALS sampled the Arctic UTLS retrieving vertical profiles of its main atmospheric targets (T, H2O, O3, HNO3, N2O, CO). The obtained vertical profiles have been used to investigate chemical and dynamical processes taking place in the Arctic atmosphere. In particular, we found the presence of filaments of vortex air during the Premier-Ex campaign and of re-nitrification or HNO3 redistribution due to sedimentation followed by evaporation of Polar Stratospheric Cloud (PSC) particles during the ESSenCe campaign. Furthermore, the results of the comparisonbetween MARSCHALS and MIPAS-STR products as well as the state of the atmosphere during the ESSenCe campaign simulated by theCLaMS (Chemical Lagrangian Model of the Stratosphere) and EMAC (ECHAM/MESSy Atmospheric Chemistry) models will be presented.

Cortesi, Ugo; Castelli, Elisa; Del Bianco, Samuele; Dinelli, Bianca Maria; Gerber, Daniel; Kerridge, Brian; Oelhaf, Hermann; Woiwode, Wolfgang; Vogel, Baerbel; Sinnhuber, Bjoern-Martin; Ruhnke, Roland

2013-04-01

321

Arctic Net  

NSDL National Science Digital Library

This network of Canadian agencies brings together scientists and managers in the natural, human health and social sciences with their partners in Inuit organizations, northern communities, federal and provincial agencies and the private sector to study the impacts of climate change in the coastal Canadian Arctic. Over 90 ArcticNet researchers from 23 Canadian universities and 5 Federal departments collaborate with research teams in the USA, Japan, Denmark, Sweden, Norway, Poland, the United Kingdom, Spain, Russia, Greenland and France. The site contains information about the background and structure of the organization as well as news and events and information about research, education and training, media and publications, and the Canadian Coast Guard Ship Amundsen, which is a combination research vessel and ice breaker. Shortcut links lead to a photograph gallery and information about Schools on Board, an outreach program to interest Canadian secondary school children in Arctic studies.

322

Arctic Meltdown  

NSDL National Science Digital Library

In 1996, US entrepreneur and explorer Gary Comer took his small boat through the Northwest Passage in 19 days, a route that had once been ice, but was now easily navigated open water. This radio broadcast weighs up the extent and implications of the imminent Arctic ice breakup. The broadcast discusses the Historical Limit line in Greenland, which denotes glacier recession; Inuit observations of climate changes that are challenging their culture; the acceleration of global warming on Arctic sea ice; the problems increased Arctic shipping and melting permafrost are creating for infrastructure; the long-term outlook for global sea levels; and the possibility for the complete melting of Greenland. The broadcast is 28 minutes and 11 seconds in length and is available in real audio format.

2011-11-29

323

Unprecedented Arctic ozone loss in 2011.  

PubMed

Chemical ozone destruction occurs over both polar regions in local winter-spring. In the Antarctic, essentially complete removal of lower-stratospheric ozone currently results in an ozone hole every year, whereas in the Arctic, ozone loss is highly variable and has until now been much more limited. Here we demonstrate that chemical ozone destruction over the Arctic in early 2011 was--for the first time in the observational record--comparable to that in the Antarctic ozone hole. Unusually long-lasting cold conditions in the Arctic lower stratosphere led to persistent enhancement in ozone-destroying forms of chlorine and to unprecedented ozone loss, which exceeded 80 per cent over 18-20 kilometres altitude. Our results show that Arctic ozone holes are possible even with temperatures much milder than those in the Antarctic. We cannot at present predict when such severe Arctic ozone depletion may be matched or exceeded. PMID:21964337

Manney, Gloria L; Santee, Michelle L; Rex, Markus; Livesey, Nathaniel J; Pitts, Michael C; Veefkind, Pepijn; Nash, Eric R; Wohltmann, Ingo; Lehmann, Ralph; Froidevaux, Lucien; Poole, Lamont R; Schoeberl, Mark R; Haffner, David P; Davies, Jonathan; Dorokhov, Valery; Gernandt, Hartwig; Johnson, Bryan; Kivi, Rigel; Kyrö, Esko; Larsen, Niels; Levelt, Pieternel F; Makshtas, Alexander; McElroy, C Thomas; Nakajima, Hideaki; Parrondo, Maria Concepción; Tarasick, David W; von der Gathen, Peter; Walker, Kaley A; Zinoviev, Nikita S

2011-10-02

324

Polar desert sandar, Antarctica  

Microsoft Academic Search

Because the climatic severity of Antarctic polar desert environments strongly inhibits glaciofluvial processes, outwash sediments are not as conspicuous as in parts of Iceland and Arctic Canada. However, in the Antarctic “dry valleys” numerous, small sandar, both active and relict, attest to the longterm effectiveness of low-magnitude, meltwater discharges in ancient polar desert landscapes. Many parts of these valley systems

R. B. Rains; M. J. Selby; C. J. R. Smith

1980-01-01

325

Polar Science Is Cool!  

ERIC Educational Resources Information Center

|Children are fascinated by the fact that polar scientists do research in extremely cold and dangerous places. In the Arctic they might be viewed as lunch by a polar bear. In the Antarctic, they could lose toes and fingers to frostbite and the wind is so fast it can rip skin off. They camp on ice in continuous daylight, weeks from any form of…

Weeks, Sophie

2012-01-01

326

Polar Explorers - Issue 18, February 2010  

NSDL National Science Digital Library

This issue of the free online magazine, Beyond Penguins and Polar Bears, explores the historical and current exploration of the Arctic and Antarctica and provides resources that help elementary teachers incorporate a study of polar explorers into their curriculum.

University, The O.

327

Spin dynamics in magnetic vortex structures  

NASA Astrophysics Data System (ADS)

This dissertation addresses spin dynamics in magnetic vortex structures, which have been experimentally investigated using time-resolved Kerr microscopy. This technique has been successfully implemented as a local spectroscopic probe to observe spin dynamics in geometrically confined magnetic structures with picosecond time resolution and spatial resolution on the order of a few hundred nanometers. Using electron-beam lithography, well-defined permalloy Ni81Fe19 disks with diameters in the range between 500 nm and 5 mum were fabricated. In the remnant state, permalloy disks form a flux-closure structure with a magnetic vortex core at the center of disk. The magnetization inside the core points out-of or into the disk plane. As the applied field decreases from a saturated state, the disks exhibit a distinct magnetization reversal process associated with the nucleation and subsequent annihilation of a magnetic vortex. The motion of a magnetic vortex, a gyrotropic mode, is directly observed in real time and space. The observed eigenfrequencies of the vortex mode as a function of disk size are in a good agreement with micromagnetic simulations. They also fall close to the predictions of a theory in which the magnetization of the displaced vortex is assumed to deform so that there are no magnetostatic charges at the edge of the disk. It is also observed that the vortex-mode eigenfrequency is nearly independent of the in-plane applied field. Azimuthal spin-wave modes, standing waves along the azimuthal direction in the vortex state, are investigated by exciting the spin system using an in-plane magnetic field pulse. Due to the cylindrical symmetry of the vortex state in remanence, two azimuthal modes propagating along opposite directions with the same number of azimuthal nodes are expected to be degenerate. However, our experimental results clearly demonstrate that the relative phase of the two azimuthal modes is determined by the polarity of the vortex core, and the magnitude of the splitting is of the same order as the vortex gyrotropic frequency. The broken degeneracy of the azimuthal spin-wave modes reveals how low-frequency excitations associated with domain structure influence spin-wave dynamics.

Park, Jooho

328

Dynamic evolution of transverse energy flow in focused asymmetric optical vector-vortex beams  

NASA Astrophysics Data System (ADS)

We present here controlled generation of asymmetric optical vector-vortex beams using a two-mode optical fiber and study the dynamic evolution of the transverse energy flow (TEF) when focused through a spherical lens. The dependence of the TEF on various factors such as the vortex charge, vortex anisotropy and polarization structure around the vortex core is explored. It is found that the TEF is directly proportional to the phase gradient and its direction is governed by the vortex charge. The presence of C-point polarization singularity in the beam and the polarization structure around it results in vibrational phase gradient which is the major factor deciding the TEF in vector-vortex beams.

Kumar, Vijay; Krishna Inavalli, V. V. G.; Viswanathan, Nirmal K.

2012-11-01

329

From vortex layers to vortex sheets  

NASA Astrophysics Data System (ADS)

This paper shows that the solution of the Birkhoff-Rott equation for the vortex sheet can be approximated, for short times, by the solutions of the Euler equation for a thin vortex layer of vorticity, when its thickness vanishes and its vorticity intensity diverges suitably. The result is obtained in an analytical setup, and an example seems to indicate that this is indeed necessary.

Benedetto, D.; Pulvirenti, M.

1992-08-01

330

High frequency spin dynamics in soft magnetic dots in biased vortex state: precise probing and nature of the eigenmodes  

Microsoft Academic Search

Regular arrays of soft magnetic dots in the vortex state are being considered as a potentially new high-density nonvolatile recording media characterized by two binary properties: chirality and polarity of magnetic vortex core. Here we unambiguously demonstrate the existence of two distinct dynamic vortex (stable and metastable) regimes with qualitatively different spin wave eigenmodes. We find that dynamic response in

Farkhad Aliev; Juan Francisco Sierra; Ahmad Awad; Gleb Kakazei; Dong-Soo Han; Sang-Koong Kim; Konstantin Guslienko; Bojan Ilic; Vitali Metlushko

2009-01-01

331

Arctic Atlas  

NSDL National Science Digital Library

In this interactive atlas adapted from UNEP/GRID-Arendal, explore different environmental features of the Arctic. Select from a list of themes to customize your map, then zoom in to take a closer look at one of six featured regions.

Foundation, Wgbh E.

2008-01-17

332

In situ measurements of the ClO/HCl ratio: Heterogeneous processing on sulfate aerosols and polar stratospheric clouds  

SciTech Connect

Simultaneous in situ measurements of stratospheric ClO and HCl have been made for the first time, during numerous flights of the ER-2 aircraft covering latitudes 24-90[degrees]N from October 1991 through March 1992. The ClO/HCl ratio is identified as a key indicator of heterogeneous processing both outside and within the Arctic polar vortex. For ClO mixing ratios below about 120 pptv, remarkably constant ClO/HCl values of about 15% characterize the lower stratosphere. The observed values are significantly higher than those derived from a 2-D model using either gas phase photochemistry alone (2%), or including heterogeneous sulfate chemistry (5-10%). During the Arctic early spring, after conversion of HCl into reactive chlorine has taken place, the vortex edge is poorly defined by ClO levels. Loss of HCl and its slow recovery following low-temperature polar heterogeneous chemistry distinguishes HCl as a new and unique dynamical tracer of PSC-processed air. 19 refs., 4 figs.

Webster, C.R.; May, R.D. (California Institute of Technology, Pasadena, CA (United States)); Toohey, D.W. (Univ. of California, Irvine, CA (United States)); Avallone, L.M.; Anderson, J.G. (Harvard Univ., Cambridge, MA (United States)); Solomon, S.

1993-11-19

333

Toxicity of Polar Bear Liver  

Microsoft Academic Search

ACCORDING to information from the Eskimos, and records from Arctic travellers, bad effects may follow the consumption, by men and dogs, of the livers of polar bear, bearded seal, Greenland fox and Eskimo huskies, whereas livers of other Arctic mammals can usually be eaten without injury.

Kaare Rodahl

1949-01-01

334

The Arctic Research Consortium of the United States (ARCUS)  

NASA Astrophysics Data System (ADS)

The Arctic Research Consortium of the United States (ARCUS) is a nonprofit membership organization composed of universities and institutions that have a substantial commitment to research in the Arctic. ARCUS was formed in 1988 to serve as a forum for planning, facilitating, coordinating, and implementing interdisciplinary studies of the Arctic; to act as a synthesizer and disseminator of scientific information on arctic research; and to educate scientists and the general public about the needs and opportunities for research in the Arctic. ARCUS, in collaboration with the broader science community, relevant agencies and organizations, and other stakeholders, coordinates science planning and educational activities across disciplinary and organizational boundaries. Examples of ARCUS projects include: - Arctic Sea Ice Outlook - an international effort that provides monthly summer reports synthesizing community estimates of the expected sea ice minimum. - Sea Ice for Walrus Outlook - a resource for Alaska Native subsistence hunters, coastal communities, and others that provides weekly reports with information on sea ice conditions relevant to walrus in Alaska waters. - PolarTREC (Teachers and Researchers Exploring and Collaborating) - a program whereby K-12 educators and researchers work together in hands-on field experiences in the Arctic and Antarctic to advance polar science education. - ArcticInfo mailing list, Witness the Arctic newsletter, and the Arctic Calendar - communication tools for the arctic science community to keep apprised of relevant news, meetings, and announcements. - Coordination for the Study of Environmental Arctic Change (SEARCH) program, which aims to provide scientific understanding of arctic environmental change to help society understand and respond to a rapidly changing Arctic.

Fox, S. E.; Wiggins, H. V.

2011-12-01

335

Cryogenic Features Of Tundra Soils Along A Bioclimate Gradient In Arctic Alaska And Canada  

Microsoft Academic Search

Previous field research describing Polar Desert soils of High Arctic, Canada, have emphasized the soils as having minimal development. However, based on recent field studies we found that cryogenesis plays a controlling role in soil formation in the High Arctic, just as in the Middle and Low Arctic. Cryoturbation is one kind of cryogenic process in that soil horizons are

C. Ping; G. J. Michaelson; C. Tarnocai; D. A. Walker

2005-01-01

336

The Stratéole-Vorcore experiment : a survey of the 2005 Antarctic winter polar vortex in the low stratosphere, using a flotilla of 25 superpressure balloons  

NASA Astrophysics Data System (ADS)

The Stratéole-Vorcore stratospheric balloon campaign took place in September-October 2005 from McMurdo Antarctica This campaign which benefited from a very significant support from the National science Foundation as well as from the French polar institute Institut Paul Emile Victor is a joint effort of the French space agency CNES and the Laboratoire de meteorology Dynamique IPSL CNRS 27 balloons were released from 5 th of September to 28 th of October Drifting during several months at constant air density in the low stratosphere they formed a flotilla of up to 21 balloons floating simultaneously The duration of flight cumulated over the entire flotilla reached 1577 days producing more than 150 000 meteorological observations This presentation will mainly focus on the description of the ground and flight systems the launch operations and the main characteristics of the flights It will be completed by an overview of the current plans for the utilisation of this observation system for other scientific missions in the near future

Cocquerez, P.; Venel, S.; Vial, F.; Mechoso, R.; Hertzog, A.; Basdevant, C.

337

A study of polar ozone depletion based on sequential assimilation of satellite data from the ENVISAT/MIPAS and Odin/SMR instruments  

NASA Astrophysics Data System (ADS)

The objective of this study is to demonstrate how polar ozone depletion can be mapped and quantified by assimilating ozone data from satellites into the wind driven transport model DIAMOND, (Dynamical Isentropic Assimilation Model for OdiN Data). By assimilating a large set of satellite data into a transport model, ozone fields can be built up that are less noisy than the individual satellite ozone profiles. The transported fields can subsequently be compared to later sets of incoming satellite data so that the rates and geographical distribution of ozone depletion can be determined. By tracing the amounts of solar irradiation received by different air parcels in a transport model it is furthermore possible to study the photolytic reactions that destroy ozone. In this study, destruction of ozone that took place in the Antarctic winter of 2003 and in the Arctic winter of 2002/2003 have been examined by assimilating ozone data from the ENVISAT/MIPAS and Odin/SMR satellite-instruments. Large scale depletion of ozone was observed in the Antarctic polar vortex of 2003 when sunlight returned after the polar night. By mid October ENVISAT/MIPAS data indicate vortex ozone depletion in the ranges 80-100% and 70-90% on the 425 and 475 K potential temperature levels respectively while the Odin/SMR data indicates depletion in the ranges 70-90% and 50-70%. The discrepancy between the two instruments has been attributed to systematic errors in the Odin/SMR data. Assimilated fields of ENVISAT/MIPAS data indicate ozone depletion in the range 10-20% on the 475 K potential temperature level, (~19 km altitude), in the central regions of the 2002/2003 Arctic polar vortex. Assimilated fields of Odin/SMR data on the other hand indicate ozone depletion in the range 20-30%.

Rösevall, J. D.; Murtagh, D. P.; Urban, J.; Jones, A. K.

2007-02-01

338

Transpolar observations of the morphological properties of Arctic sea ice  

Microsoft Academic Search

During the 5 August to 30 September 2005 Healy Oden Trans-Arctic Expedition a trans-Arctic survey of the physical properties of the polar ice pack was conducted. The observational program consisted of four broad classes of snow and ice characterization activities: observations made while the ship was in transit, ice station measurements, helicopter survey flights, and the deployment of autonomous ice

Donald K. Perovich; Thomas C. Grenfell; Bonnie Light; Bruce C. Elder; Jeremy Harbeck; Christopher Polashenski; Walter B. Tucker III; Casey Stelmach

2009-01-01

339

Coupled Vortex Oscillations in Spatially Separated Permalloy Squares  

SciTech Connect

We experimentally study the magnetization dynamics of pairs of micron-sized permalloy squares coupled via their stray fields. The trajectories of the vortex cores in the Landau-domain patterns of the squares are mapped in real space using time-resolved scanning transmission x-ray microscopy. After excitation of one of the vortex cores with a short magnetic-field pulse, the system behaves like coupled harmonic oscillators. The coupling strength depends on the separation between the squares and the configuration of the vortex-core polarizations. Considering the excitation via a rotating in-plane magnetic field, it can be understood that only a weak response of the second vortex core is observed for equal core polarizations.

Vogel, Andreas; Kamionka, Thomas; Martens, Michael; Meier, Guido [Institut fuer Angewandte Physik und Zentrum fuer Mikrostrukturforschung, Universitaet Hamburg, 20355 Hamburg (Germany); Drews, Andre [Institut fuer Angewandte Physik und Zentrum fuer Mikrostrukturforschung, Universitaet Hamburg, 20355 Hamburg (Germany); Arbeitsbereich Technische Informatik Systeme, Universitaet Hamburg, 22527 Hamburg (Germany); Chou, Kang Wei; Tyliszczak, Tolek [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, 94720 California (United States); Stoll, Hermann [Max-Planck-Institut fuer Metallforschung, 70569 Stuttgart (Germany); Van Waeyenberge, Bartel [Department of Solid State Sciences, Ghent University, 9000 Ghent (Belgium)

2011-04-01

340

Influence of Mountain Waves and NAT Nucleation Mechanisms on Polar Stratospheric Cloud Formation at Local and Synoptic Scales during the 1999-2000 Arctic Winter.  

National Technical Information Service (NTIS)

A scheme for introducing mountain wave-induced temperature perturbations in a microphysical polar stratospheric cloud (PSC) model has been developed. A data set of temperature fluctuations attributable to mountain waves as computed by the Mountain Wave Fo...

B. Knudsen E. V. Browell N. Larsen S. D. Eckermann S. H. Svendsen

2005-01-01

341

Synchronicity of Aerosol Optical Measurements acquired at Arctic and sub-Arctic sites  

NASA Astrophysics Data System (ADS)

The ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) campaign during the spring of 2008 provided a unique opportunity to compare and interpret a variety of airborne, groundbased and satellite aerosol measurments. In this communication we focus on the Arctic-wide interpretation of sunphotometry measurements acquired at a variety of Arctic and sub-Arctic sites and their link with available lidar and satellite data. The presentation will focus on sites in Barrow, Alaska (NOAA Earth System Research Laboratory), the PEARL (Polar Environment Atmospheric Research Laboratory) Arctic observatory in Eureka, Nunavut (Canada) and AEROCAN / AERONET sites in Resolute Bay, Nunavut, Yellowknife, Northwest Territories (Canada), and Iquluit, Nunavut. Emphasis will be placed on the synchronicity and propagation of extensive and intensive aerosol properties.

O'Neill, N. T.; Saha, A.; Stone, R.; Abboud, I.; McArthur, B.; Freemantle, J.; Baibakov, K.

2008-12-01

342

Detection and Analysis of Thin Ice Clouds-Aerosol-Precipitation Interactions Over Polar Regions During Winter  

NASA Astrophysics Data System (ADS)

Recent findings from AQUA satellites and ground based observations at PEARL, Eureka NU, together with concurring model simulations over the Arctic are leading us into a new perspective on the formation of cold- anomalies in the High Arctic through the interactions of aerosol, clouds, precipitation and radiation. Our results show that vast regions of thin ice cloud (TIC) formations (1000 to 4000 km wide and 5 to 10 km deep) are modified by anthropogenic aerosols deeply penetrating in the Arctic troposphere during the cold season. The cold cores of dissipating winter storms are often carrying heat, moisture, pollution and angular momentum far inside the polar vortex. There, the otherwise dominant stratified air is forced to mix deeply by cold lows. It results in slow lifting of moist cold air also enriched by anthropogenic and acidic aerosols. Observations and model simulations agree in showing the maximum aerosol concentrations in the upper troposphere often occurs in the winter Polar vortex. The combined IR and slow adiabatic cooling of cold air in decaying lows favours the interaction between aerosols, originating from arctic haze, and clouds. The TIC forms on acid coated particles, deactivating IFN and leading to fewer but larger ice crystals. As a result, precipitation of large crystals, which are analogous to diamond dust but in deep layers (6-8km) that cover vast regions (1000s km), is enhenced, resulting in effective depletion of water vapor at cold temperatures. The process effectively dehydrates the air deep into the troposphere and produces precipitating cloud types that are markedly distinct from those dominating more pristine regions, such as Greenland and Antarctica. Statistics on aerosol and TIC found in both polar regions are compared. Microphysical processes in TIC and light precipitation occurring in these regions are enhancing the loss of energy in the far IR region and can be responsible for profound alteration of the production rate of cold anomalies which eventually feed into midlatitude synoptic storms. This study is part of the research activities during the International Polar Year.

Blanchet, J.; Grenier, P.; Munoz-Alpizar, R.; Ayash, T.; Girard, E.; Jones, C.; Stephens, G.; Jiang, J. H.

2008-05-01

343

Improved vortex reactor system  

DOEpatents

An improved vortex reactor system for affecting fast pyrolysis of biomass and Refuse Derived Fuel (RDF) feed materials comprising: a vortex reactor having its axis vertically disposed in relation to a jet of a horizontally disposed steam ejector that impels feed materials from a feeder and solids from a recycle loop along with a motive gas into a top part of said reactor.

Diebold, James P. (Lakewood, CO); Scahill, John W. (Evergreen, CO)

1995-01-01

344

Vortex diode jet  

DOEpatents

A fluid transfer system that combines a vortex diode with a jet ejector to transfer liquid from one tank to a second tank by a gas pressurization method having no moving mechanical parts in the fluid system. The vortex diode is a device that has a high resistance to flow in one direction and a low resistance to flow in the other.

Houck, Edward D. (Idaho Falls, ID)

1994-01-01

345

Vortex diode jet.  

National Technical Information Service (NTIS)

A fluid transfer system that combines a vortex diode with a jet ejector to transfer liquid from one tank to a second tank by a gas pressurization method having no moving mechanical parts in the fluid system. The vortex diode is a device that has a high re...

E. D. Houck

1993-01-01

346

The Arctic Research Consortium of the United States (ARCUS)  

NASA Astrophysics Data System (ADS)

The Arctic Research Consortium of the United States (ARCUS) is a nonprofit membership organization composed of universities and institutions that have a substantial commitment to research in the Arctic. ARCUS was formed in 1988 to serve as a forum for planning, facilitating, coordinating, and implementing interdisciplinary studies of the Arctic; to act as a synthesizer and disseminator of scientific information on arctic research; and to educate scientists and the general public about the needs and opportunities for research in the Arctic. ARCUS, in collaboration with the broader science community, relevant agencies and organizations, and other stakeholders, coordinates science planning and educational activities across disciplinary and organizational boundaries. Examples of current ARCUS science planning activities include: serving as the project office for the multi-agency Study of Environmental Arctic Change (SEARCH) program, providing support to the related Bering Ecosystem Study (BEST), and serving as the Science Management Office for the National Science Foundation (NSF) Arctic System Science (ARCSS) Program. ARCUS’ central educational activity is PolarTREC (Teachers and Researchers Exploring and Collaborating), an International Polar Year (IPY) program whereby K-12 educators and researchers work together in hands-on field experiences in the Arctic and Antarctic to advance polar science education. Additional science planning, educational, information, and outreach activities include, among many others, the Witness the Arctic newsletter, the Arctic Visiting Speakers’ Series, the ArcticInfo listserve, the Internet Media Archive (IMA), and the annual Arctic Forum conference. More information about these and other ARCUS activities can be found at the ARCUS website at: http://www.arcus.org.

Creek, K. R.; Fox, S. E.; Wiggins, H. V.

2010-12-01

347

Experimental observation of a tripolar vortex in a plasma  

NASA Astrophysics Data System (ADS)

A tripolar vortex, three aligned vortices with alternate signs of polarity of rotation, has been observed in a plasma for the first time. The tripolar vortex always appears with a deep density depression in the neutral particles, and the rotation direction of each vortex is opposite to that of the E×B rotation due to the ambipolar electric field. It is shown that a net momentum transfer during the charge-exchange interaction produces an effective force acting on the ions. The present experiment shows that this effective force may dominate the ambipolar-electric field and drive the anti-E×B vortical motion of ions.

Okamoto, A.; Hara, K.; Nagaoka, K.; Yoshimura, S.; Vranješ, J.; Kono, M.; Tanaka, M. Y.

2003-06-01

348

Nonlinear vortex dynamics and transient domains in ferromagnetic disks  

NASA Astrophysics Data System (ADS)

We report a time-resolved imaging and micromagnetic simulation study of the relaxation dynamics of a magnetic vortex in the nonlinear regime. We use time-resolved photoemission electron microscopy and micromagnetic calculations to examine the emergence of nonlinear vortex dynamics in patterned Ni80Fe20 disks in the limit of long field pulses. We show for core shifts beyond ˜20%-25% of the disk radius, the initial motion is characterized by distortions of the vortex, a transient cross-tie wall state, and instabilities in the core polarization that influence the core trajectories.

Cheng, X. M.; Buchanan, K. S.; Divan, R.; Guslienko, K. Y.; Keavney, D. J.

2009-05-01

349

Harnessing Optical Vortex Lattices in Nematic Liquid Crystals  

NASA Astrophysics Data System (ADS)

By creating self-induced vortexlike defects in the nematic liquid crystal layer of a light valve, we demonstrate the realization of programable lattices of optical vortices with arbitrary distribution in space. On each lattice site, every matter vortex acts as a photonic spin-to-orbital momentum coupler and an array of circularly polarized input beams is converted into an output array of vortex beams with topological charges consistent with the matter lattice. The vortex arrangements are explained on the basis of light-induced matter defects of both signs and consistent topological rules.

Barboza, R.; Bortolozzo, U.; Assanto, G.; Vidal-Henriquez, E.; Clerc, M. G.; Residori, S.

2013-08-01

350

Fractional vortex in asymmetric 0-? long Josephson junctions  

NASA Astrophysics Data System (ADS)

We consider an infinitely long 0-? Josephson junction consisting of 0 and ? regions having different critical current densities jc,0 and jc,?. The ground state of such a junction corresponds to a spontaneously formed asymmetric semifluxon with tails decaying on different length scales. We calculate the depinning current of such a fractional vortex and show that it is different for positive and negative bias polarity. We also show that upon application of a bias current, the fractional flux (topological charge) associated with the vortex changes. We calculate the range of fractional flux associated with the vortex when the bias changes from negative to positive critical (depinning) values.

Goldobin, E.; Kleiner, R.; Koelle, D.

2013-06-01

351

Arctic Languages: An Awakening.  

ERIC Educational Resources Information Center

|This work is a study of Arctic languages written in an interdisciplinary manner. Part of the Unesco Arctic project aimed at safeguarding the linguistic heritage of Arctic peoples, the book is the outcome of three Unesco meetings at which conceptual approaches to and practical plans for the study of Arctic cultures and languages were worked out.…

Collis, Dermid R. F., Ed.

352

Arctic Languages: An Awakening.  

ERIC Educational Resources Information Center

This work is a study of Arctic languages written in an interdisciplinary manner. Part of the Unesco Arctic project aimed at safeguarding the linguistic heritage of Arctic peoples, the book is the outcome of three Unesco meetings at which conceptual approaches to and practical plans for the study of Arctic cultures and languages were worked out.…

Collis, Dermid R. F., Ed.

353

Forecast, measurement, and modeling of an unprecedented polar ozone filament event over Mauna Loa Observatory, Hawaii  

Microsoft Academic Search

In mid-March 2005 the northern lower stratospheric polar vortex experienced a severe stretching episode, bringing a large polar filament far south of Alaska toward Hawaii. This meridional intrusion of rare extent, coinciding with the polar vortex final warming and breakdown, was followed by a zonal stretching in the wake of the easterly propagating subtropical main flow. This caused polar air

Om Prakash Tripathi; Thierry Leblanc; I. Stuart McDermid; Frank Lefèvre; Marion Marchand; Alain Hauchecorne

2006-01-01

354

Carbon sources for lake food webs in the Canadian High Arctic and other regions of Arctic North America  

Microsoft Academic Search

We investigated the role of autochthonous and terrestrial carbon in supporting aquatic food webs in the Canadian High Arctic\\u000a by determining the diet of the dominant primary consumer, aquatic chironomids. These organisms were studied in fresh waters\\u000a on 3 islands of the Arctic Archipelago (~74–76°N) including barren polar desert watersheds and a polar oasis with lush meadows.\\u000a Stomach content analysis

John Chételat; Louise Cloutier; Marc Amyot

2010-01-01

355

Second harmonic generation in magnetic nanoparticles with vortex magnetic state  

NASA Astrophysics Data System (ADS)

Nonlinear optical properties of a regular array of triangular-shaped vortex magnetic nanoparticles is studied using the optical second harmonic generation (SHG) technique. We demonstrate that the SHG azimuthal anisotropy is consistent with the 3m symmetry of individual Co nanodots placed in a square surface lattice. Qualitatively different SHG magnetic hysteresis loops are obtained for circular and linear polarizations of the fundamental radiation. In the first case, a wide SHG hysteresis at zero DC magnetic field H is observed, which is attributed to a macroscopic magnetic toroid moment in Co nanodots induced by a noncentrosymmetric distribution of the magnetization. On the contrary, for the linear pump polarization the SHG loop is similar to observed commonly in linear magnetooptics for vortex magnetic structures and reveals a rather narrow width at H=0. A phenomenological SHG description based on the introduction of the SHG polarization induced by a magnetic toroid moment in vortex magnetic nanostructures is presented.

Krutyanskiy, V. L.; Kolmychek, I. A.; Gribkov, B. A.; Karashtin, E. A.; Skorohodov, E. V.; Murzina, T. V.

2013-09-01

356

Sea ice occurrence predicts genetic isolation in the Arctic fox.  

PubMed

Unlike Oceanic islands, the islands of the Arctic Sea are not completely isolated from migration by terrestrial vertebrates. The pack ice connects many Arctic Sea islands to the mainland during winter months. The Arctic fox (Alopex lagopus), which has a circumpolar distribution, populates numerous islands in the Arctic Sea. In this study, we used genetic data from 20 different populations, spanning the entire distribution of the Arctic fox, to identify barriers to dispersal. Specifically, we considered geographical distance, occurrence of sea ice, winter temperature, ecotype, and the presence of red fox and polar bear as nonexclusive factors that influence the dispersal behaviour of individuals. Using distance-based redundancy analysis and the BIOENV procedure, we showed that occurrence of sea ice is the key predictor and explained 40-60% of the genetic distance among populations. In addition, our analysis identified the Commander and Pribilof Islands Arctic populations as genetically unique suggesting they deserve special attention from a conservation perspective. PMID:17868292

Geffen, Eli; Waidyaratne, Sitara; Dalén, Love; Angerbjörn, Anders; Vila, Carles; Hersteinsson, Pall; Fuglei, Eva; White, Paula A; Goltsman, Michael; Kapel, Christian M O; Wayne, Robert K

2007-09-14

357

2011 Arctic ozone depletion as seen by ESA-ENVISAT Atmospheric-Chemistry sensors  

NASA Astrophysics Data System (ADS)

Three Atmospheric-Chemistry sensors on-board the ENVISAT satellite (GOMOS, MIPAS, and SCIAMACHY) sound the Earth's atmosphere since about nine years and provide to the science community three separated, but complementary data sets of the most interesting atmospheric trace gases. These extended and coherent data sets, generated with ESA operational processors, give a historical overview over seasonal and long-term trends of geophysical parameters and allow investigating major atmospheric phenomena and natural events. During March 2011, ESA's satellite ENVISAT detected the severe ozone depletion above the Euro-Atlantic sector of the Northern Hemisphere. This record-breaking loss for the ozone layer over the North Pole was mainly caused by unusual polar vortex conditions characterized by very low temperatures in the Arctic stratosphere. This paper presents the chemical ozone depletion over the Arctic regions as detected by SCIAMACHY, MIPAS and GOMOS during spring of 2011. Global maps of total ozone column and vertical ozone profiles along the mission's lifetime clearly show the unprecedented Arctic ozone loss for 2011 with the subsequent migration of ozone depleted air masses towards lower latitudes. ENVISAT's atmospheric measurements reveal changes in the composition of the ozone-related chemical species and permit to point out the chemical correlations of the ozone distribution with nitrogen and chlorine compounds and with the evolution of stratospheric temperatures. The synergistic use of ESA operational data sets from the three instruments allows to closely monitor the occurrence and extension of seasonal ozone depletion events, and to draw a comprehensive picture of all chemistry processes involved in the full atmospheric range.

Brizzi, G.; Niro, F.; Saavedra de Miguel, L.; Dehn, A.; Scarpino, G.; Fehr, T.; von Kuhlmann, R.

2011-12-01

358

Arctic air chemistry: Haze analysis  

NASA Astrophysics Data System (ADS)

The microparticulate (i.e., aerosol) and gas concentrations in Arctic air masses are being assessed currently as a result of a large-scale, multinational cooperative study made this spring. It turns out that many of the ideas about the origin of Arctic haze, industrial pollution, soil particles from the great desert regions of eastern China and Mongolia, and seasonal effects, to name a few, may all be valid. A recent report about the first extended airborne measurements of Arctic haze that were made during March and April of this year stated: “Most of the scientists on board the NOAA plane found the haze to be much denser and more extensive than they anticipated” (Environ. Sci. Technol., June 1983). The results of WP-30 Orion research aircraft flights over the Arctic ice cap suggest that in some locations the haze extends upward of 8.5 km at this time of the year. The haze was found to exist at all latitudes in the northern polar region with unbroken continuity to an altitude of approximately 3 km. At higher altitudes there was a banding of discontinuous haze layers.

Bell, Peter M.

359

Vortex crystals in fluids  

NASA Astrophysics Data System (ADS)

It is common in geophysical flows to observe localized regions of enhanced vorticity. This observation can be used to derive model equations to describe the motion and interaction of these localized regions, or vortices, and which are simpler than the original PDEs. The best known vortex model is derived from the incompressible Euler equations, and treats vortices as points in the plane. A large part of this dissertation utilizes this particular model, but we also survey other point vortex and weakly viscous models. The main focus of this thesis is an object known as the vortex crystal. These remarkable configurations of vortices maintain their basic shapes for long times, while perhaps rotating or translating rigidly in space. We study existence and stability of families of vortex crystals in the special case where N vortices have small and equal circulation and one vortex has large circulation. As the small circulation tends to zero, the weak vortices tend to a circle centered on the strong vortex. A special potential function of this limiting problem can be used to characterize orbits and stability. Whenever a critical point of this function is nondegenerate, we prove that the orbit can be continued via the Implicit Function Theorem, and its linear stability is determined by the eigenvalues of the Hessian matrix of the potential. For general N, we find at least three distinct families of critical points, one of which continues to a linearly stable class of vortex crystals. Because the stable family is most likely to be observed in nature, we study it extensively. Continuation methods allow us to follow these critical points to nonzero weak vortex strength and investigate stability and bifurcations. In the large N limit of this family, we prove that there is a unique one parameter family of distributions which minimize a "generalized" potential. Finally, we use point vortex and weakly viscous vortex models to analyze vortex crystal configurations observed in hurricane eyes and related numerical simulations. We find striking numerical and analytical agreement, thus validating the use of simplified vortex models to describe geophysical phenomena.

Barry, Anna M.

360

Trends in long-term gaseous mercury observations in the Arctic and effects of temperature and other atmospheric conditions  

NASA Astrophysics Data System (ADS)

Gaseous elemental mercury (GEM) measurements at Alert, Canada, from 1995 to 2007 were analyzed for statistical time trends and for correlations with meteorological and climate data. A significant decreasing trend in annual GEM concentration is reported at Alert, with an estimated slope of -0.0086 ng m-3 yr-1 (-0.6% yr-1) over this 13-year period. It is shown that there has been a shift in the month of minimum mean GEM concentration from May to April due to a change in the timing of springtime atmospheric mercury depletion events (AMDEs). These AMDEs are found to decrease with increasing local temperature within each month, both at Alert and at Amderma, Russia. These results support the temperature dependence suggested by previous experimental results and theoretical kinetic calculations on both bromine generation and mercury oxidation and highlight the potential for changes in Arctic mercury chemistry with climate. A correlation between total monthly AMDEs at Alert and the Polar/Eurasian Teleconnection Index was observed only in March, perhaps due to higher GEM inputs in early spring in those years with a weak polar vortex. A correlation of AMDEs at Alert with wind direction supports the origin of mercury depletion events over the Arctic Ocean, in agreement with a previous trajectory study of ozone depletion events. Interannual variability in total monthly depletion event frequency at Alert does not appear to correlate significantly with total or first-year northern hemispheric sea ice area or with other major teleconnection patterns. Nor do AMDEs at either Alert or Amderma correlate with local wind speed, as might be expected if depletion events are sustained by stable, low-turbulence atmospheric conditions. The data presented here - both the change in timing of depletion events and their relationship with temperature - can be used as additional constraints to improve the ability of models to predict the cycling and deposition of mercury in the Arctic.

Cole, A. S.; Steffen, A.

2010-05-01

361

Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions  

NASA Astrophysics Data System (ADS)

Significant reductions in stratospheric ozone occur inside the polar vortices each spring when chlorine radicals produced by heterogeneous reactions on cold particle surfaces in winter destroy ozone mainly in two catalytic cycles, the ClO dimer cycle and the ClO/BrO cycle. Chlorofluorocarbons (CFCs), which are responsible for most of the chlorine currently present in the stratosphere, have been banned by the Montreal Protocol and its amendments, and the ozone layer is predicted to recover to 1980 levels within the next few decades. During the same period, however, climate change is expected to alter the temperature, circulation patterns and chemical composition in the stratosphere, and possible geo-engineering ventures to mitigate climate change may lead to additional changes. To realistically predict the response of the ozone layer to such influences requires the correct representation of all relevant processes. The European project RECONCILE has comprehensively addressed remaining questions in the context of polar ozone depletion, with the objective to quantify the rates of some of the most relevant, yet still uncertain physical and chemical processes. To this end RECONCILE used a broad approach of laboratory experiments, two field missions in the Arctic winter 2009/10 employing the high altitude research aircraft M55-Geophysica and an extensive match ozone sonde campaign, as well as microphysical and chemical transport modelling and data assimilation. Some of the main outcomes of RECONCILE are as follows: (1) vortex meteorology: the 2009/10 Arctic winter was unusually cold at stratospheric levels during the six-week period from mid-December 2009 until the end of January 2010, with reduced transport and mixing across the polar vortex edge; polar vortex stability and how it is influenced by dynamic processes in the troposphere has led to unprecedented, synoptic-scale stratospheric regions with temperatures below the frost point; in these regions stratospheric ice clouds have been observed, extending over >106km2 during more than 3 weeks. (2) Particle microphysics: heterogeneous nucleation of nitric acid trihydrate (NAT) particles in the absence of ice has been unambiguously demonstrated; conversely, the synoptic scale ice clouds also appear to nucleate heterogeneously; a variety of possible heterogeneous nuclei has been characterised by chemical analysis of the non-volatile fraction of the background aerosol; substantial formation of solid particles and denitrification via their sedimentation has been observed and model parameterizations have been improved. (3) Chemistry: strong evidence has been found for significant chlorine activation not only on polar stratospheric clouds (PSCs) but also on cold binary aerosol; laboratory experiments and field data on the ClOOCl photolysis rate and other kinetic parameters have been shown to be consistent with an adequate degree of certainty; no evidence has been found that would support the existence of yet unknown chemical mechanisms making a significant contribution to polar ozone loss. (4) Global modelling: results from process studies have been implemented in a prognostic chemistry climate model (CCM); simulations with improved parameterisations of processes relevant for polar ozone depletion are evaluated against satellite data and other long term records using data assimilation and detrended fluctuation analysis. Finally, measurements and process studies within RECONCILE were also applied to the winter 2010/11, when special meteorological conditions led to the highest chemical ozone loss ever observed in the Arctic. In addition to quantifying the 2010/11 ozone loss and to understand its causes including possible connections to climate change, its impacts were addressed, such as changes in surface ultraviolet (UV) radiation in the densely populated northern mid-latitudes.

von Hobe, M.; Bekki, S.; Borrmann, S.; Cairo, F.; D'Amato, F.; Di Donfrancesco, G.; Dörnbrack, A.; Ebersoldt, A.; Ebert, M.; Emde, C.; Engel, I.; Ern, M.; Frey, W.; Griessbach, S.; Grooß, J.-U.; Gulde, T.; Günther, G.; Hösen, E.; Hoffmann, L.; Homonnai, V.; Hoyle, C. R.; Isaksen, I. S. A.; Jackson, D. R.; Jánosi, I. M.; Kandler, K.; Kalicinsky, C.; Keil, A.; Khaykin, S. M.; Khosrawi, F.; Kivi, R.; Kuttippurath, J.; Laube, J. C.; Lefèvre, F.; Lehmann, R.; Ludmann, S.; Luo, B. P.; Marchand, M.; Meyer, J.; Mitev, V.; Molleker, S.; Müller, R.; Oelhaf, H.; Olschewski, F.; Orsolini, Y.; Peter, T.; Pfeilsticker, K.; Piesch, C.; Pitts, M. C.; Poole, L. R.; Pope, F. D.; Ravegnani, F.; Rex, M.; Riese, M.; Röckmann, T.; Rognerud, B.; Roiger, A.; Rolf, C.; Santee, M. L.; Scheibe, M.; Schiller, C.; Schlager, H.; Siciliani de Cumis, M.; Sitnikov, N.; Søvde, O. A.; Spang, R.; Spelten, N.; Stordal, F.; Sumi?ska-Ebersoldt, O.; Viciani, S.; Volk, C. M.; vom Scheidt, M.; Ulanovski, A.; von der Gathen, P.; Walker, K.; Wegner, T.; Weigel, R.; Weinbuch, S.; Wetzel, G.; Wienhold, F. G.; Wintel, J.; Wohltmann, I.; Woiwode, W.; Young, I. A. K.; Yushkov, V.; Zobrist, B.; Stroh, F.

2012-11-01

362

Polaronic pinning of vortex in magnetic superconductors and magnetic-superconducting multilayers  

NASA Astrophysics Data System (ADS)

We present a new type of vortex pinning by enhancing the viscosity of vortex in magnetic superconductors with long relaxation time of magnetization and large magnetic susceptibility. In the absence of current, vortices are dressed by nonuniform magnetic polarization and form vortex-polarons. Under a small current and consequently low Lorentz force, the magnetic polarization follows the vortex motion. However, at long magnetic relaxation time of magnetization, there is additional dragging force by the magnetization besides the Bardeen-Stephen one, thus the effective viscosity of vortex is significantly enhanced resulting in suppression of dissipation. For a large current, the magnetic polarization cannot follow the vortex motion and the vortex-polaron dissociates, i.e. the magnetization and vortex become decoupled. In the IV characteristic, the decoupling transition shows as a voltage jump and can be identified as a depinning transition. The polaronic pinning mechanism successfully explains the observed enhancement of critical current in the ErNiBC superconductor at low temperatures. The polaronic pinning can be optimized in magnetic-superconducting multilayers. We show also that vortex-polaron creep is suppressed at low temperatures.

Lin, Shi-Zeng; Bulaevskii, Lev

2013-03-01

363

Dynamics of magnetic vortex core switching in Fe nanodisks by applying in-plane magnetic field pulse  

NASA Astrophysics Data System (ADS)

We investigated the influence of the magnetic field pulse parameters and the size of the Fe element to the vortex core switching by micromagnetic modeling. When the magnetic field pulse with an appropriate strength and duration is applied to 30 nm thick Fe circular disks with diameters between 100 nm and 1 ?m, the vortex configuration is perturbed away from the equilibrium state, and the circular symmetric distribution of the in-plane magnetization around the vortex core deforms. This leads to the creation of a new vortex core with the opposite polarity and an antivortex. With increasing time, the vortex-antivortex pair annihilates. As a result of the annihilation, a single vortex core with opposite polarity remains and a vortex core switch is realized. The process of core switching, however, strongly depends on the amplitude and duration of the magnetic pulse.

Xiao, Q. F.; Rudge, J.; Girgis, E.; Kolthammer, J.; Choi, B. C.; Hong, Y. K.; Donohoe, G. W.

2007-11-01

364

In situ measurements of BrO in the Arctic stratosphere  

Microsoft Academic Search

Mixing ratios of BrO have been measured in the Arctic lower stratosphere with an instrument mounted on the NASA ER-2 aircraft. Observations from fourteen flights above the Arctic Circle in January and February of 1989 defined mixing ratios within the vortex of 4{plus minus}2 parts per trillion by volume (pptv) at a potential temperature of 400 K, rising to 8{plus

D. W. Toohey; J. G. Anderson; W. H. Brune; K. R. Chan

1990-01-01

365

The surface UV-B irradiation in the Arctic: observations at the Polish polar station, Hornsund \\/(77°N,15°E), 1996-1997  

Microsoft Academic Search

Measurements of the UV-B radiation reaching ground level at the Polish polar station, Hornsund (Svalbard, 77°N, \\/15°30'E, 11 m a.s.l.), have been carried out since February 1996 by means of a temperature stabilized Robertson-Berger-type meter. The seasonal pattern of UV dose and UV index, and factors affecting the UV-B level there are studied for the period March-October of 1996 and

J. W. Krzyscin; P. S. Sobolewski

2001-01-01

366

The surface UV-B irradiation in the Arctic: observations at the Polish polar station, Hornsund (77°N,15°E), 1996–1997  

Microsoft Academic Search

Measurements of the UV-B radiation reaching ground level at the Polish polar station, Hornsund (Svalbard, 77°N, 15°30?E, 11 m a.s.l.), have been carried out since February 1996 by means of a temperature stabilized Robertson–Berger-type meter. The seasonal pattern of UV dose and UV index, and factors affecting the UV-B level there are studied for the period March–October of 1996 and

Janusz W. Krzy?cin; Piotr S. Sobolewski

2001-01-01

367

Optical vortex coronagraph.  

PubMed

We describe a method to observe dim exoplanets that eliminates light from the parent star across the entire exit pupil without sacrificing light from the planet by use of a vortex mask of topological charge m = 2. PMID:16389814

Foo, Gregory; Palacios, David M; Swartzlander, Grover A

2005-12-15

368

Reversal of the dipole vortex in a negative index of refraction material  

Microsoft Academic Search

When a small particle is illuminated by a circularly polarized laser beam, the induced electric dipole moment rotates in a plane. The flow lines of the emitted electromagnetic energy are the field lines of the Poynting vector. When the particle is embedded in a dielectric, these field lines have a vortex structure, and the rotation in the vortex has the

Xin Li; Henk F. Arnoldus

2010-01-01

369

Wave–Vortex Interactions  

Microsoft Academic Search

\\u000a This chapter presents a theoretical investigation of wave–vortex interactions in fluid systems of interest to atmosphere and\\u000a ocean dynamics. The focus is on strong interactions in the sense that the induced changes in the vortical flow should be significant. In essence, such strong wave–vortex\\u000a interactions require significant changes in the potential vorticity (PV) of the flow either by advection of

O. Bühler

2010-01-01

370

Improved vortex reactor system  

DOEpatents

An improved vortex reactor system is described for affecting fast pyrolysis of biomass and Refuse Derived Fuel (RDF) feed materials comprising: a vortex reactor having its axis vertically disposed in relation to a jet of a horizontally disposed steam ejector that impels feed materials from a feeder and solids from a recycle loop along with a motive gas into a top part of said reactor. 12 figs.

Diebold, J.P.; Scahill, J.W.

1995-05-09

371

Vortex diode jet  

SciTech Connect

A fluid transfer system is described that combines a vortex diode with a jet ejector to transfer liquid from one tank to a second tank by a gas pressurization method having no moving mechanical parts in the fluid system. The vortex diode is a device that has a high resistance to flow in one direction and a low resistance to flow in the other. 10 figures.

Houck, E.D.

1994-05-17

372

Arctic Warming - a Perspective from Svalbard  

Microsoft Academic Search

During the International Polar Year many projects connected to IGBP science will be implemented, mostly within the Arctic and Antarctic areas. This glaciology project is connected to the IPY via the projects IPY-GLACIODYN and IPY-KINNVIKA, and has been carried out since 1997 on the Lomosovfonna ice field on central Spitsbergen in the Svalbard archipelago, and, in this respect, has a

V. Pohjola

2007-01-01

373

Arctic and Antarctic Birds: Unit Outlines  

NSDL National Science Digital Library

This article assembles free resources from the Arctic and Antarctic Birds issue of the Beyond Penguins and Polar Bears cyberzine into a unit outline based on the 5E learning cycle framework. Outlines are provided for Grades K-2 and 3-5.

Fries-Gaither, Jessica; Shiverdecker, Terry

374

Radiative consequences of recent Arctic variability  

Microsoft Academic Search

Surface cloud forcing in polar regions may either be positive, and encourage warming and ice melt, or negative, and cool or promote re-freeze. Prior to 2001, the cloud forcing calculated at the Arctic surface in polynyas and leads indicated that the clouds were preferentially scattering light, leading to a cooling or negative forcing. However, in recent years, pronounced sea ice

E. L. Key; P. J. Minnett

2005-01-01

375

The large-scale frozen-in anticyclone in the 2011 Arctic summer stratosphere  

NASA Astrophysics Data System (ADS)

The 2011 Arctic stratospheric final warming was characterized by a large-scale frozen-in anticyclone (FrIAC) that rapidly displaced the winter polar vortex, establishing unusually strong polar easterlies. A comprehensive overview of the 2011 FrIAC is provided using meteorological analyses, Microwave Limb Sounder (MLS) N2O observations, and N2O simulations from the Global Modeling Initiative (GMI) 3-D chemistry and transport model and the Van Leer Icosahedral Triangular Advection (VITA) 2-D (latitude × longitude) isentropic transport model. A vortex edge diagnostic is used to determine the FrIAC boundary, allowing quantification of several FrIAC properties. The 2011 FrIAC originated over North Africa in late March and traveled eastward and poleward over 2 weeks, forming a strong anticyclone that extended from ~580-2100 K potential temperature (~25-50 km). Low potential vorticity (PV) was transported to the pole with the FrIAC in early April; during May, most of the PV signature decayed due to diabatic processes. A small remnant negative PV anomaly persisted near the pole until mid-June. Tracer equivalent latitude was low initially and remained low throughout the summer. GMI, VITA, and MLS showed elevated N2O in the FrIAC, although the peak value was smaller in GMI due to a subtropical low bias. The high-resolution (~20 km) VITA filamentary structure quantitatively matched most of the features observed by MLS when smoothed to match the MLS resolution. The high-N2O anomaly persisted in the middle stratosphere over 4 months until late August, when it was destroyed by horizontal and vertical shearing, combined with photochemical processes.

Allen, Douglas R.; Douglass, Anne R.; Strahan, Susan E.

2013-03-01

376

Chiral-specific electron-vortex-beam spectroscopy  

NASA Astrophysics Data System (ADS)

Chiral electron-vortex beams, carrying a well-defined orbital angular momentum (OAM) about the propagation axis, are potentially useful as probes of magnetic and other chiral materials. We present an effective operator, expressible in a multipolar form, describing the inelastic processes in which electron-vortex beams interact with atoms, including those present in Bose-Einstein condensates, involving exchange of OAM. We show clearly that the key properties of the processes are dependent on the dynamical state and location of the atoms involved as well as the vortex-beam characteristics. Our results can be used to identify scenarios in which chiral-specific electron-vortex spectroscopy can probe magnetic sublevel transitions normally studied using circularly polarized photon beams with the advantage of atomic-scale spatial resolution.

Yuan, J.; Lloyd, S. M.; Babiker, M.

2013-09-01

377

Ferromagnetic resonance force spectroscopy of a magnetic vortex  

NASA Astrophysics Data System (ADS)

Due to its nanometer size (of the order the exchange length), probing the high frequency dynamics of a magnetic vortex core is an experimental challenge. Precessional dynamics of the magnetization of individual nano-disks of NiMnSb perpendicularly magnetized is measured in a wide range of bias magnetic fields using a magnetic resonance force microscope (MRFM). A full dynamic phase diagram, demonstrating excitation of a Kittel-type dipolar mode in the saturated disks and the gyrotropic mode of vortex core rotation in the vortex-state unsaturated disks, is established. Switching of the vortex core polarity in a negative (anti-parallel to core) bias magnetic field is registered dynamically. Analytic theory and micromagnetic simulations provide a quantitative description of the experimental results.

de Loubens, G.; Klein, O.; Riegler, A.; Lochner, F.; Schmidt, G.; Molenkamp, L. W.; Hurdequint, H.; Boust, F.; Vukadinovic, N.; Slavin, A. N.

2009-03-01

378

Evaluation of Whole Atmosphere Community Climate Model simulations of ozone during Arctic winter 2004-2005  

NASA Astrophysics Data System (ADS)

The work presented here evaluates polar stratospheric ozone simulations from the Whole Atmosphere Community Climate Model (WACCM) for the Arctic winter of 2004-2005. We use the Specified Dynamics version of WACCM (SD-WACCM), in which temperatures and winds are nudged to meteorological assimilation analysis results. Model simulations of ozone and related constituents generally compare well to observations from the Earth Observing System Microwave Limb Sounder (MLS). At most times, modeled ozone agrees with MLS data to within ~10%. However, a systematic high bias in ozone in the model of ~18% is found in the lowermost stratosphere in March. We attribute most of this ozone bias to too little heterogeneous processing of halogens late in the winter. We suggest that the model under-predicts ClONO2 early in the winter, which leads to less heterogeneous processing and too little activated chlorine. Model HCl could also be overestimated due to an underestimation of HCl uptake into supercooled ternary solution (STS) particles. In late winter, the model overestimates gas-phase HNO3, and thus NOy, which leads to an over-prediction of ClONO2 (under-prediction of activated chlorine). A sensitivity study, in which temperatures for heterogeneous chemistry reactions were reduced by 1.5 K, shows significant improvement of modeled ozone. Chemical ozone loss is inferred from the MLS observations using the pseudo-passive subtraction approach. The inferred ozone loss using this method is in agreement with or less than previous independent results for the Arctic winter of 2004-2005, reaching 1.0 ppmv on average and up to 1.6 ppmv locally in the polar vortex.

Brakebusch, M.; Randall, C. E.; Kinnison, D. E.; Tilmes, S.; Santee, M. L.; Manney, G. L.

2013-03-01

379

Logic operations based on magnetic-vortex-state networks.  

PubMed

Logic operations based on coupled magnetic vortices were experimentally demonstrated. We utilized a simple chain structure consisting of three physically separated but dipolar-coupled vortex-state Permalloy disks as well as two electrodes for application of the logical inputs. We directly monitored the vortex gyrations in the middle disk, as the logical output, by time-resolved full-field soft X-ray microscopy measurements. By manipulating the relative polarization configurations of both end disks, two different logic operations are programmable: the XOR operation for the parallel polarization and the OR operation for the antiparallel polarization. This work paves the way for new-type programmable logic gates based on the coupled vortex-gyration dynamics achievable in vortex-state networks. The advantages are as follows: a low-power input signal by means of resonant vortex excitation, low-energy dissipation during signal transportation by selection of low-damping materials, and a simple patterned-array structure. PMID:22533663

Jung, Hyunsung; Choi, Youn-Seok; Lee, Ki-Suk; Han, Dong-Soo; Yu, Young-Sang; Im, Mi-Young; Fischer, Peter; Kim, Sang-Koog

2012-05-02

380

The Migration of Polar Bears.  

National Technical Information Service (NTIS)

As the polar bear roams widely over its Arctic habitat in quest of its principal food--seal meat, little is known about him. Now a technique is at hand that promises to fill some of the gaps in our knowledge of the polar bear's life. The technique involve...

V. Flyger M. R. Townsend

1968-01-01

381

Airborne investigation of Arctic tropospheric ozone depletions  

NASA Astrophysics Data System (ADS)

After polar sunrise, tropospheric ozone experiences episodic depletions for a few months, down to sub-ppb levels, before stabilizing into the summer. These ozone depletion episodes (ODEs), first discovered in the early 1980s, have been studied extensively from observatories on the shores of the Arctic Ocean, and are now understood to be due to bromine chemistry. However, it is still unclear where and how the bromine enters the atmosphere from the oceanic interface. This is due to the fact that the Arctic Ocean remains very difficult and expensive to access for in-situ measurements, and that satellite-based methods cannot resolve the trace gases of interest, on the required time scales, with the exception of bromine oxide. The PAM-ARCMIP ("Polar Airborne Measurements and Arctic Regional Climate Model Simulation Project"), a multi-year program to improve our understanding of physical processes in the inner Arctic, provides an opportunity to investigate the location, spatial extent and vertical characteristics of ozone depletions over the Arctic Ocean. Over 5 weeks in the spring of 2011, 32 research flights were conducted spanning the Arctic from Barrow, Alaska, over the Canadian Archipelago and Greenland to Longyearbyen, Spitsbergen. In-situ ozone measurements in the lower troposphere over the Arctic Ocean, with frequent vertical profiling, were performed with a UV photometric analyzer. The first 8 research flights also had on board a LIDAR for nadir profiles of the ozone concentration. An analysis of ozone in relation to aerosol particles, hydrometeors, boundary layer and ice cover characteristics will be presented.

Staebler, R. M.; Liu, P. S.; Strapp, W.; Whiteway, J. A.; Haas, C.; Herber, A.; Neuber, R.

2011-12-01

382

The extremely cold 2009-2010 winter and its relationship with the Arctic oscillation  

NASA Astrophysics Data System (ADS)

The Northern-Hemisphere high-latitude continents experienced extremely cold weathers in winter 2009-2010. In the present paper, we show that the cold winter was associated with the activity of the Arctic oscillation (AO), which demonstrated the strongest negative polarity over the past six decades and persisted from December, 2009 to March, 2010. It is found that variations of the surface AO was closely linked to stratospheric polar vortex anomalies, and that the surface AO phases followed downward propagation of stratospheric Northern-Hemisphere Annular mode (NAM) anomalies during the winter. The case of 2009-2010 winter provides us with a typical example that anomalous stratospheric signals can be used to improve skills of long-range weather forecast and intra-seasonal climate prediction in winter time. We also show that the El Niño event, which started developing from May 2009, might contribute the formation of exceptionally negative and persistent AO and stratospheric NAM, particularly over North Pacific and North America.

Wen, Xin-Yu; Hu, Yong-Yun; Liu, Ji-Ping

2013-10-01

383

Dynamical characterization of the 2010/2011 winter Arctic ozone depletion replaced in a climatologic context  

NASA Astrophysics Data System (ADS)

The 2010/2011 stratospheric winter has recorded one of the strongest ozone depletion in the Arctic region since observations began. Such phenomenon is currently very difficult to predict as it strongly depends on winter dynamical conditions. The aim of this study is to characterize winter/spring dynamical stratospheric conditions and the ozone depletion yield. We used the AURA-MLS (Microwave Limb Sounder) measurements, the ECMWF (European Centre for Medium-Range Weather Forecasts) Era-Interim meteorological fields and the results of the potential vorticity contour advection model MIMOSA (Modélisation Isentrope du transport Méso-échelle de l'Ozone Stratosphérique par Advection). Dynamical processes associated with the 2010/2011 winter have been investigated and replaced in a climatologic context by comparing this winter to previous similar and different winter/spring seasons over the last 20 years. Preliminary results show that the polar night jet in 2010/2011 was of an extraordinary strength during February-March, as for the same period in 1995/1996 where the ozone depletion was close to 30 %. Using MIMOSA model, we also show that the polar vortex during February-March 2010/2011 was more centred above the pole than the climatologic location. Wave activity and heat fluxes deduced from ECMWF data allow us to evaluate the specific conditions encountered during this 2010/2011 winter and mechanisms which lead to such extreme situation.

Thiéblemont, R.; Huret, N.; Hauchecorne, A.; Drouin, M.

2011-12-01

384

Ground-based measurements of stratospheric ClO over Spitzbergen in the Arctic spring of 1997  

NASA Astrophysics Data System (ADS)

We have measured stratospheric chlorine monoxide (ClO) at Ny Ålesund (79°N), on the Arctic island of Spitzbergen, during the spring of 1997 as part of a ground-based millimeter-wave radiometer intercomparison campaign. The presence of ClO in the stratosphere is a direct result of the catalytic destruction of ozone by chlorine and can provide a good measure of this process. Spitzbergen remained well inside the strong, cold polar spring vortex of 1997 during most of our observation period, which ran from February 7 through March 17. Measurements show a strong enhancement of lower stratospheric ClO from mid-February through mid-March, in substantial agreement with other measurements, and consistent with increasing daily exposure to photolytic processes liberating active chlorine. A comparison of these results with ClO observations made at McMurdo Station (78°S), Antarctica, during the austral spring of 1997 shows ClO amounts in the Arctic stratosphere that were comparable to Antarctic stratospheric values when temperatures and solar exposures were similar over a relatively short time.

Nagar, V. C.; McDonald, M. K.; de Zafra, R. L.

1999-09-01

385

Arctic Rabies - A Review  

PubMed Central

Rabies seems to persist throughout most arctic regions, and the northern parts of Norway, Sweden and Finland, is the only part of the Arctic where rabies has not been diagnosed in recent time. The arctic fox is the main host, and the same arctic virus variant seems to infect the arctic fox throughout the range of this species. The epidemiology of rabies seems to have certain common characteristics in arctic regions, but main questions such as the maintenance and spread of the disease remains largely unknown. The virus has spread and initiated new epidemics also in other species such as the red fox and the racoon dog. Large land areas and cold climate complicate the control of the disease, but experimental oral vaccination of arctic foxes has been successful. This article summarises the current knowledge and the typical characteristics of arctic rabies including its distribution and epidemiology.

M?rk, Torill; Prestrud, Pal

2004-01-01

386

Alaskan Arctic Tundra.  

National Technical Information Service (NTIS)

Alaskan Arctic Tundra is the proceedings volume of the 25th Anniversary Celebration of the Naval Arctic Research Laboratory (NARL). There are 15 papers in the proceedings -- 7 speeches, 7 technical papers, and an introduction. Each technical paper focuses...

M. E. Britton

1973-01-01

387

Vertical structure of recent Arctic warming.  

PubMed

Near-surface warming in the Arctic has been almost twice as large as the global average over recent decades-a phenomenon that is known as the 'Arctic amplification'. The underlying causes of this temperature amplification remain uncertain. The reduction in snow and ice cover that has occurred over recent decades may have played a role. Climate model experiments indicate that when global temperature rises, Arctic snow and ice cover retreats, causing excessive polar warming. Reduction of the snow and ice cover causes albedo changes, and increased refreezing of sea ice during the cold season and decreases in sea-ice thickness both increase heat flux from the ocean to the atmosphere. Changes in oceanic and atmospheric circulation, as well as cloud cover, have also been proposed to cause Arctic temperature amplification. Here we examine the vertical structure of temperature change in the Arctic during the late twentieth century using reanalysis data. We find evidence for temperature amplification well above the surface. Snow and ice feedbacks cannot be the main cause of the warming aloft during the greater part of the year, because these feedbacks are expected to primarily affect temperatures in the lowermost part of the atmosphere, resulting in a pattern of warming that we only observe in spring. A significant proportion of the observed temperature amplification must therefore be explained by mechanisms that induce warming above the lowermost part of the atmosphere. We regress the Arctic temperature field on the atmospheric energy transport into the Arctic and find that, in the summer half-year, a significant proportion of the vertical structure of warming can be explained by changes in this variable. We conclude that changes in atmospheric heat transport may be an important cause of the recent Arctic temperature amplification. PMID:18172495

Graversen, Rune G; Mauritsen, Thorsten; Tjernström, Michael; Källén, Erland; Svensson, Gunilla

2008-01-01

388

Direct observation of imprinted antiferromagnetic vortex state in CoO/Fe/Ag(001) disks  

SciTech Connect

In magnetic thin films, a magnetic vortex is a state in which the magnetization vector curls around the center of a confined structure. A vortex state in a thin film disk, for example, is a topological object characterized by the vortex polarity and the winding number. In ferromagnetic (FM) disks, these parameters govern many fundamental properties of the vortex such as its gyroscopic rotation, polarity reversal, core motion, and vortex pair excitation. However, in antiferromagnetic (AFM) disks, though there has been indirect evidence of the vortex state through observations of the induced FM-ordered spins in the AFM disk, they have never been observed directly in experiment. By fabricating single crystalline NiO/Fe/Ag(001) and CoO/Fe/Ag(001) disks and using X-ray Magnetic Linear Dichroism (XMLD), we show direct observation of the vortex state in an AFM disk of AFM/FM bilayer system. We observe that there are two types of AFM vortices, one of which has no analog in FM structures. Finally, we show that a frozen AFM vortex can bias a FM vortex at low temperature.

Wu, J.; Carlton, D.; Park, J. S.; Meng, Y.; Arenholz, E.; Doran, A.; Young, A.T.; Scholl, A.; Hwang, C.; Zhao, H. W.; Bokor, J.; Qiu, Z. Q.

2010-12-21

389

Molecular evolution of haemoglobins of polar fishes  

Microsoft Academic Search

The Arctic and the Antarctic differ by age and isolation of the respective marine faunas. Antarctic fish are highly stenothermal, in response to stable water temperatures, whereas the Arctic ones are exposed to seasonal and latitudinal temperature variations. The knowledge of the mechanisms of phenotypic response to cold exposure in species of both polar habitats offers fundamental insights into the

Cinzia Verde; Daniela Giordano; Guido di Prisco

2006-01-01

390

Canadian Arctic vegetation mapping  

Microsoft Academic Search

During the next few decades the Arctic is expected to experience unprecedented changes in climate and resource development. All of these will potentially aVect land use and vegetation cover. There is a need for a comprehens- ive and consistent circumpolar map of arctic vegetation that will be useful for modelling vegetation change in the circumpolar region. The Canadian arctic vegetation

W. A. Gould; S. Edlund; S. Zoltai; M. Raynolds; D. A. Walker; H. Maier

2002-01-01

391

Vortex Domains in Ferroelectric Nano-Structures  

NASA Astrophysics Data System (ADS)

Recently the study of submicron-diameter ferroelectric disks and squares and rectangles fabricated from films of ca. 100-300 nm thick have revealed usual domain patterns, qualitatively different from the stripe domains commonly studied in macroscopic specimens in the past. These include doughnut-shaped domains, four-fold vertex closure domains, and fractal domains. The static configurations offer a variety of puzzles, and the structures differ from those in magnetic vortex domains, presumably due to the much larger anisotropy in ferroelectrics, which generally prohibits true vortex configurations with polarization forced out of plane. The dynamics also differ qualitatively from early studies: For decades ferroelectrics were thought to be highly Ising-like, but recent data and theoretical simulations favor Bloch walls and more Heisenberg-like kinetics. This talk will include data from Alina Schilling and Marty Gregg in Belfast, Marin Alexe in Halle, and modeling from Hlinka and Marton in Prague and Bellaiche and Prosandeev in Arkansas.

Scott, James F.

2011-03-01

392

Size distribution time series of a polar stratospheric cloud observed above Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) (69°N) and analyzed from multiwavelength lidar measurements during winter 2005  

NASA Astrophysics Data System (ADS)

A case study of a polar stratospheric cloud (PSC) is described using multiwavelength (355, 532, and 1064 nm) lidar measurements performed at the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) on 6 December 2005. Rotational Raman signals at 529 and 530 nm are used to derive a temperature field within the cloud using the rotational Raman technique (RRT). The PSC size distributions are retrieved between 1500 and 2000 UTC through a combination of statistical filtering and best match approaches. Several PSC types were detected between 22 and 26 km during the measurement session. Liquid ternary aerosols are identified before about 1600 and after 1900 UTC typically; their averaged retrieved size distribution parameters and associated errors at the backscatter peak are: No ? 1-10 cm-3 (50%), rm ? 0.15 ?m (20%), and ? ? 1.2 (15%). A mode of much larger particles is detected between 1600 and 1900 UTC (No ? 0.04 cm-3 (30%), rm ? 1.50 ?m (15%), and ? ? 1.37 (10%). The different PSC types are also identified using standard semiempirical classifications, based on lidar backscatter, temperature, and depolarization. Overall, the characteristics of the retrieved size distributions are consistent with these classifications. They all suggest that these very large particles are certainly nitric acid trihydrate that could have been generated by the strong gravity wave activity visible in the temperature profiles. The results demonstrate that multiwavelength lidar data coupled to both RRT temperatures and our size distribution retrieval can provide useful additional information for identification of PSC types and for direct comparisons with microphysical model simulations.

Jumelet, Julien; Bekki, Slimane; David, Christine; Keckhut, Philippe; Baumgarten, Gerd

2009-01-01

393

Vortex Characterization for Engineering Applications  

SciTech Connect

Realistic engineering simulation data often have features that are not optimally resolved due to practical limitations on mesh resolution. To be useful to application engineers, vortex characterization techniques must be sufficiently robust to handle realistic data with complex vortex topologies. In this paper, we present enhancements to the vortex topology identification component of an existing vortex characterization algorithm. The modified techniques are demonstrated by application to three realistic data sets that illustrate the strengths and weaknesses of our approach.

Jankun-Kelly, M; Thompson, D S; Jiang, M; Shannahan, B; Machiraju, R

2008-01-30

394

Wave modes of collective vortex gyration in dipolar-coupled-dot-array magnonic crystals.  

PubMed

Lattice vibration modes are collective excitations in periodic arrays of atoms or molecules. These modes determine novel transport properties in solid crystals. Analogously, in periodical arrangements of magnetic vortex-state disks, collective vortex motions have been predicted. Here, we experimentally observe wave modes of collective vortex gyration in one-dimensional (1D) periodic arrays of magnetic disks using time-resolved scanning transmission x-ray microscopy. The observed modes are interpreted based on micromagnetic simulation and numerical calculation of coupled Thiele equations. Dispersion of the modes is found to be strongly affected by both vortex polarization and chirality ordering, as revealed by the explicit analytical form of 1D infinite arrays. A thorough understanding thereof is fundamental both for lattice vibrations and vortex dynamics, which we demonstrate for 1D magnonic crystals. Such magnetic disk arrays with vortex-state ordering, referred to as magnetic metastructure, offer potential implementation into information processing devices. PMID:23877284

Han, Dong-Soo; Vogel, Andreas; Jung, Hyunsung; Lee, Ki-Suk; Weigand, Markus; Stoll, Hermann; Schütz, Gisela; Fischer, Peter; Meier, Guido; Kim, Sang-Koog

2013-01-01

395

Quantum vortex reconnections  

NASA Astrophysics Data System (ADS)

We study reconnections of quantum vortices by numerically solving the governing Gross-Pitaevskii equation. We find that the minimum distance between vortices scales differently with time before and after the vortex reconnection. We also compute vortex reconnections using the Biot-Savart law for vortex filaments of infinitesimal thickness, and find that, in this model, reconnections are time symmetric. We argue that the likely cause of the difference between the Gross-Pitaevskii model and the Biot-Savart model is the intense rarefaction wave which is radiated away from a Gross-Pitaeveskii reconnection. Finally we compare our results to experimental observations in superfluid helium and discuss the different length scales probed by the two models and by experiments.

Zuccher, S.; Caliari, M.; Baggaley, A. W.; Barenghi, C. F.

2012-12-01

396

The structure of vortex breakdown  

Microsoft Academic Search

The term 'vortex breakdown', as used in the reported investigation, refers to a disturbance characterized by the formation of an internal stagnation point on the vortex axis, followed by reversed flow in a region of limited axial extent. Two forms of vortex breakdown, which predominate, are shown in photographs. One form is called 'near-axisymmetric' (sometimes 'axisymmetric'), and the other is

S. Leibovich

1978-01-01

397

AMALi - the Airborne Mobile Aerosol Lidar for Arctic research  

Microsoft Academic Search

The Airborne Mobile Aerosol Lidar (AMALi) is an instrument developed at the Alfred Wegener Institute for Polar and Marine Research for reliable operation under the challenging weather conditions at the Earth's polar regions. Since 2003 the AMALi has been successfully deployed for measurements in ground-based installation and zenith- or nadir-pointing airborne configurations during several scientific campaigns in the Arctic. The

I. S. Stachlewska; R. Neuber; A. Lampert; C. Ritter; G. Wehrle

2010-01-01

398

Ozone Chemistry during the 2002 Antarctic Vortex Split  

Microsoft Academic Search

In September 2002, the Antarctic polar vortex was disturbed, and it split into two parts caused by an unusually early stratospheric major warming. This study discusses the chemical consequences of this event using the Chemical Lagrangian Model of the Stratosphere (CLaMS). The chemical initialization of the simulation is based on Halogen Occultation Experiment (HALOE) measurements. Because of its Lagrangian nature,

Jens-Uwe Grooß; Paul Konopka; Rolf Müller

2005-01-01

399

Vortex pairs on surfaces  

SciTech Connect

A pair of infinitesimally close opposite vortices moving on a curved surface moves along a geodesic, according to a conjecture by Kimura. We outline a proof. Numerical simulations are presented for a pair of opposite vortices at a close but nonzero distance on a surface of revolution, the catenoid. We conjecture that the vortex pair system on a triaxial ellipsoid is a KAM perturbation of Jacobi's geodesic problem. We outline some preliminary calculations required for this study. Finding the surfaces for which the vortex pair system is integrable is in order.

Koiller, Jair [Centro de Matematica Aplicada, FGV/RJ, Praia de Botafogo 190 Rio de Janeiro, RJ, 22250-40 (Brazil); Boatto, Stefanella [Instituto de Matematica da UFRJ, C.P. 68530, Cidade Universitaria Rio de Janeiro, RJ 21945-970 (Brazil)

2009-05-06

400

First order vortex dynamics  

SciTech Connect

A non-dissipative model for vortex motion in thin superconductors is considered. The Lagrangian is a Galilean invariant version of the Ginzburg{endash}Landau model for time-dependent fields, with kinetic terms linear in the first time derivatives of the fields. It is shown how, for certain values of the coupling constants, the field dynamics can be reduced to first order differential equations for the vortex positions. Two vortices circle around one another at constant speed and separation in this model. {copyright} 1997 Academic Press, Inc.

Manton, N.S. [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB3 9EW (England)

1997-05-01

401

Polar Oceans - Issue 14, May 2009  

NSDL National Science Digital Library

This issue of the free online magazine, Beyond Penguins and Polar Bears, explores the characteristics and living systems of the Arctic and Southern Oceans. Instructional resources include ocean-related lessons and informational text about blue whales.

University, The O.

402

Islands of the Arctic  

NASA Astrophysics Data System (ADS)

Few environments on Earth are changing more dramatically than the Arctic. Sea ice retreat and thinning is unprecedented in the period of the satellite record. Surface air temperatures are the warmest in centuries. The biology of Arctic lakes is changing like never before in millennia. Everything is pointing to the meltdown predicted by climate model simulations for the next 100 years. At the same time, the Arctic remains one of the most pristine and beautiful places on Earth. For both those who know the Arctic and those who want to know it, this book is worth its modest price. There is much more to the Arctic than its islands, but there's little doubt that Greenland and the major northern archipelagos can serve as a great introduction to the environment and magnificence of the Arctic. The book uses the islands of the Arctic to give a good introduction to what the Arctic environment is all about. The first chapter sets the stage with an overview of the geography of the Arctic islands, and this is followed by chapters that cover many key aspects of the Arctic: the geology (origins), weather and climate, glaciers, ice sheets, sea ice, permafrost and other frozen ground issues, coasts, rivers, lakes, animals, people, and environmental impacts. The material is pitched at a level well suited for the interested layperson, but the book will also appeal to those who study the science of the Arctic.

Overpeck, Jonathan

2004-02-01

403

Structural units of the central arctic and their relations to the mesozoic arctic plume  

Microsoft Academic Search

The integration of information obtained from onshore and offshore geological and geophysical research undertaken in the context\\u000a of the International Polar Year has led to the following results. The continental crust is widespread in the Arctic not only\\u000a beneath the shelves of polar seas in the framework of the Amerasia Basin but also in the Chukchi-Northwind, Lomonosov, and\\u000a Mendeleev ridges;

N. I. Filatova; V. E. Khain

2009-01-01

404

Arctic climate tipping points.  

PubMed

There is widespread concern that anthropogenic global warming will trigger Arctic climate tipping points. The Arctic has a long history of natural, abrupt climate changes, which together with current observations and model projections, can help us to identify which parts of the Arctic climate system might pass future tipping points. Here the climate tipping points are defined, noting that not all of them involve bifurcations leading to irreversible change. Past abrupt climate changes in the Arctic are briefly reviewed. Then, the current behaviour of a range of Arctic systems is summarised. Looking ahead, a range of potential tipping phenomena are described. This leads to a revised and expanded list of potential Arctic climate tipping elements, whose likelihood is assessed, in terms of how much warming will be required to tip them. Finally, the available responses are considered, especially the prospects for avoiding Arctic climate tipping points. PMID:22270703

Lenton, Timothy M

2012-02-01