M.K. SEJRD. KRAUSE-JENSENS. RYSGAARDL.L. SORENSEN...
8页查看更多>>摘要：Annual air–sea exchange ofCO_2 inYoung Sound,NEGreenlandwas estimated using pCO_2 surface-water measurements during summer (2006–2009) and during an ice-covered winter 2008. All surface pCO_2 values were below atmospheric levels indicating an uptake of atmospheric CO_2. During sea ice formation, dissolved inorganic carbon (DIC) content is reduced causing sea ice to be under saturated in CO_2. Approximately 1% of the DIC forced out of growing sea ice was released into the atmosphere while the remaining 99% was exported to the underlying water column. Sea ice covered the fjord 9 months a year and thereby efficiently blocked air–sea CO_2 exchange. During sea ice melt, dissolution of C_aCO_3 combined with primary production and strong stratification of the water column acted to lower surface-water pCO_2 levels in the fjord. Also, a large input of glacial melt water containing geochemically reactive carbonate minerals may contribute to the low surface-water pCO_2 levels. The average annual uptake of atmospheric CO_2was estimated at 2.7 mol CO_2m~(-2 )yr~(-1) or 32 gCm~(-2 )yr~(-1) for the study area, which is lower than estimates from the Greenland Sea.Variability in duration of sea ice cover caused significant year-to-year variation in annual gas exchange.
原文链接:
NSTL
Taylor & Francis
SOREN RYSGAARDJORGEN BENDTSENBRUNO DELILLEGERHARD S. DIECKMANN...
8页查看更多>>摘要：Although salt rejection from sea ice is a key process in deep-water formation in ice-covered seas, the concurrent rejection of CO_2 and the subsequent effect on air–sea CO_2 exchange have received little attention. We review the mechanisms by which sea ice directly and indirectly controls the air–sea CO_2 exchange and use recent measurements of inorganic carbon compounds in bulk sea ice to estimate that oceanic CO_2 uptake during the seasonal cycle of sea-ice growth and decay in ice-covered oceanic regions equals almost half of the net atmospheric CO_2 uptake in ice-free polar seas. This sea-ice driven CO_2 uptake has not been considered so far in estimates of global oceanic CO_2 uptake. Net CO_2 uptake in sea-ice–covered oceans can be driven by; (1) rejection during sea–ice formation and sinking of CO_2-rich brine into intermediate and abyssal oceanic water masses, (2) blocking of air–sea CO_2 exchange during winter, and (3) release of CO_2-depleted melt water with excess total alkalinity during sea-ice decay and (4) biological CO_2 drawdown during primary production in sea ice and surface oceanic waters.
原文链接:- NSTL
- Taylor & Francis
T. COLOMBOP. BONASONIP. CRISTOFANELLIF. CALZOLARI...
12页查看更多>>摘要：Thework focuses on the analysis ofCO_2 andO_3 surface variations observed during five summer experimental campaigns carried out at the ‘Icaro Camp’ clean air facility (74.7°S, 164.1°E, 41 m a.s.l.) of the ‘Mario Zucchelli’ Italian coastal research station. This experimental activity allowed the definition of summer average background O_3 values that ranged from 18.3±4.7 ppbv (summer 2005–2006) to 21.3 ± 4.0 ppbv (summer 2003–2004). Background CO_2 concentrations showed an average growth rate of 2.10 ppmv yr~(–1), with the highest CO_2 increase between the summer campaigns 2002–2003 and 2001–2002 (+2.85 ppmv yr~(–1)), probably reflecting the influence of the 2002/2003 ENSO event. A comparison with other Antarctic coastal sites suggested that the summer background CO_2 and O_3 at MZS-IC are well representative of the average conditions of the Ross Sea coastal regions. As shown by the analysis of local wind direction and by 3-D back-trajectory calculations, the highest CO_2 and O_3 values were recorded in correspondence to air masses flowing from the interior of the Antarctic continent. These results suggest that air mass transport from the interior of the continent exerts an important influence on air mass composition in Antarctic coastal areas.
原文链接:- NSTL
- Taylor & Francis
J. CRAWFORDS. CHAMBERSA. G. WILLIAMSW. ZAHOROWSKI...
17页查看更多>>摘要：Two-point radon gradients provide a direct, unambiguous measure of near-surface atmospheric mixing. A 31-month data set of hourly radon measurements at 2 and 50 m is used to characterize the seasonality and diurnal variability of radon concentrations and gradients at a site near Sydney. Vertical differencing allows separation of remote (fetchrelated) effects on measured radon concentrations from those due to diurnal variations in the strength and extent of vertical mixing. Diurnal composites, grouped according to the maximum nocturnal radon gradient (C_(max)), reveal strong connections between radon, wind, temperature and mixing depth on subdiurnal timescales. Comparison of the bulk Richardson Number (Ri_B) and the turbulence kinetic energy (TKE) with the radon-derived bulk diffusivity (K_B) helps to elucidate the relationship between thermal stability, turbulence intensity and the resultant mixing. On nights with large C_(max), K_B and TKE levels are low and RiB is well above the ‘critical’ value. Conversely, when C_(max) is small, K-B and TKE levels are high and RiB is near zero. For intermediate C_(max), however, Ri_B remains small whereas TKE and K_B both indicate significantly reduced mixing. The relationship between stability and turbulence is therefore non-linear, with even mildly stable conditions being sufficient to suppress mixing.
原文链接:- NSTL
- Taylor & Francis
HARALD E. RIEDERLEONHARDT M. JANCSOSTEFANIA DI ROCCOJOHANNES STAEHELIN...
15页查看更多>>摘要：We apply methods from extreme value theory to identify extreme events in high (termed EHOs) and low (termed ELOs) total ozone and to describe the distribution tails (i.e. very high and very low values) of five long-term European ground-based total ozone time series. The influence of these extreme events on observed mean values, long-term trends and changes is analysed. The results show a decrease in EHOs and an increase in ELOs during the last decades, and establish that the observed downward trend in column ozone during the 1970–1990s is strongly dominated by changes in the frequency of extreme events. Furthermore, it is shown that clear ‘fingerprints’ of atmospheric dynamics (NAO,ENSO) and chemistry [ozone depleting substances (ODSs), polar vortex ozone loss] can be found in the frequency distribution of ozone extremes, even if no attribution is possible from standard metrics (e.g. annual mean values). The analysis complements earlier analysis for the world’s longest total ozone record at Arosa, Switzerland, confirming and revealing the strong influence of atmospheric dynamics on observed ozone changes. The results provide clear evidence that in addition to ODS, volcanic eruptions and strong/moderate ENSO and NAO events had significant influence on column ozone in the European sector.
原文链接:- NSTL
- Taylor & Francis
JOST HEINTZENBERGMARKUS HERMANNANDREAS WEIGELTANTONY CLARKE...
16页查看更多>>摘要：This study extrapolates aerosol data of the CARIBIC project from 1997 until June 2008 in along trajectories to compose large-scale maps and vertical profiles of submicrometre particle concentrations in the upper troposphere and lowermost stratosphere (UT/LMS). The extrapolation was validated by comparing extrapolated values with CARIBIC data measured near the respective trajectory position and by comparing extrapolated CARIBIC data to measurements by other experiments near the respective trajectory positions. Best agreement between extrapolated and measured data is achieved with particle lifetimes longer than the maximum length of used trajectories. The derived maps reveal regions of strong and frequent new particle formation, namely the Tropical Central and Western Africa with the adjacent Atlantic, South America, the Caribbean and Southeast Asia. These regions of particle formation coincide with those of frequent deep convective clouds. Vertical particle concentration profiles for the troposphere and the stratosphere confirm statistically previous results indicating frequent new particle formation in the tropopause region. There was no statistically significant increase in Aitken mode particle concentration between the first period of CARIBIC operation,1997–2002, and the second period, 2004–2009. However, a significant increase in concentration occurred within the latter period when considering it in isolation.
原文链接:- NSTL
- Taylor & Francis
DEAN A. HEGGANTONY D. CLARKESARAH J. DOHERTYJOHAN STROM...
10页查看更多>>摘要：Simultaneous measurements of aerosol black carbon (BC) in both fresh snow and in air on Svalbard are presented.From these, washout ratios for BC are calculated and compared to sparse previous measurements of this metric in the arctic. The current ratios are significantly higher than previously found measured values. We argue that the degree of snow riming within the accretion zone can explain most of this difference. Using an analytical model of the scavenging process, BC scavenging efficiencies are estimated to lie in the range 0.25–0.5, comparable to measured values.
原文链接:- NSTL
ROLF WELLERDIETMAR WAGENBACHMICHEL LEGRANDCHRISTOPH ELS ASSER...
19页查看更多>>摘要：The aerosol climatology at the coastal Antarctic Neumayer Station (NM) was investigated based on continuous, 25-yr long observations of biogenic sulphur components (methanesulfonate and non–sea salt sulphate), sea salt and nitrate.Although significant long-term trends could only be detected for nitrate (-3.6±2.5% per year between 1983 and 1993 and +4.0±3.2% per year from 1993–2007), non-harmonic periodicities between 2 and 5 yr were typical for all species. Dedicated time series analyses revealed that relations to sea ice extent and various circulation indices are weak at best or not significant. In particular, no consistent link between sea ice extent and sea salt loadings was evident suggesting only a rather local relevance of the NM sea salt record. Nevertheless, a higher Southern Annular Mode index tended to entail a lower biogenic sulphur signal. In examining the spatial uniformity of the NM findings we contrasted them to respective 17 yr records from the coastal Dumont d’Urville Station. We found similar long-term trends for nitrate, indicating an Antarctic-wide but not identifiable atmospheric signal, although any significant impact of solar activity or pollution could be ruled out. No inter-site variability on the multiannual scale was evident for the other ionic compounds.
原文链接:- NSTL
- Taylor & Francis
CHRISTOPH ELSASSERDIETMAR WAGENBACHROLF WELLERMATTHIAS AUER...
15页查看更多>>摘要：We investigated the variability of ~(210)Pb, 7Be and 10Be in coastal Antarctic aerosol samples based on continuous,monthly and annually resolved time series obtained from Neumayer Station over the period 1983 to 2008. Clear seasonal cycles peaking in the local summer half year stand out as a common feature of all three radionuclide records. Time series analyses suggest that significant multiannual changes are confined to a 4–6 yr periodicity resembling that of the Southern Annual Mode index in case of ~(210)Pb and to the expected decadal solar cycle in case of the cosmogenic Be-isotopes. Both, changes in the meridional transport and surface inversion strength appear to drive the seasonal ~(210)Pb cycle, which generally peaks in November. In contrast, stratospheric air mass intrusions are proved to be the main reason for the Be-isotopes seasonality. This finding is revealed by enhanced ~(10)Be/~7Be ratios occurring during late summer / early autumn broadly concurrently with the individual Be-isotopes and the ~7Be/~(210)Pb ratio. The ~(10)Be and ~7Be records clearly reflect the decadal, solar-modulated production signal but, for unknown reasons, they substantially differ in their detailed pattern. It is ruled out, that an excess ~7Be production by solar energetic particles was responsible for this mismatch.
原文链接:- NSTL
- Taylor & Francis
M. VOGTE.D. NILSSONL. AHLME.M. MARTENSSON...
17页查看更多>>摘要：Size resolved aerosol and gas fluxes were measured in Stockholm from 1 April 2008 to 15 April 2009 over both urban and green sectors. CO_2 and H_2O fluxes peaked in daytime for all seasons. CO_2 concentrations peaked in winter. Due to vegetation influence the CO_2 fluxes had different diurnal cycles and magnitude in the two sectors. In the urban sector, CO_2 fluxes indicated a net source. The sector dominated by residential areas and green spaces had its highest aerosol fluxes in winter. In spring, super micrometer concentrations for both sectors were significantly higher, as were the urban sector rush hour fluxes. The submicrometer aerosol fluxes had a similar diurnal pattern with daytime maxima for all seasons. This suggests that only the super micrometer aerosol emissions are dependent on season. During spring there was a clear difference in super micrometer fluxes between wet and dry streets. Our direct flux measurements have improved the understanding of the processes behind these aerosol emissions. They support the hypothesis that the spring peak in aerosol emissions are due to road dust, produced during the winter, but not released in large quantities until the roads dry up during spring, and explain why Stockholm has problems meeting the EU directive for aerosol mass (PM_(10)).
原文链接:- NSTL
Stockholm Univ Press
