Polar cap absorption events of November 2001 at Terra Nova Bay, Antarctica

Abstract. Polar cap absorption (PCA) events recorded during November 2001 are investigated by observations of ionospheric absorption of a 30MHz riometer installed at Terra Nova Bay (Antarctica), and of solar proton flux, monitored by the NOAA-GOES8 satellite in geo-synchronous orbit. During this period three solar proton events (SPE) on 4, 19 and 23 November occurred. Two of these are among the dozen most intense events since 1954 and during the current solar cycle (23rd), the event of 4 November shows the greatest proton flux at energies >10MeV. Many factors contribute to the peak intensity of the two SPE biggest events, one is the Coronal Mass Ejection (CME) speed, other factors are the ambient population of SPE and the shock front due to the CME. During these events absorption peaks of several dB (~20dB) are observed at Terra Nova Bay, tens of minutes after the impact of fast halo CMEs on the geomagnetic field. Results of a cross-correlation analysis show that the first hour of absorption is mainly produced by 84–500MeV protons in the case of the 4 November event and by 15–44MeV protons for the event of 23 November, whereas in the entire event the contribution to the absorption is due chiefly to 4.2–82MeV (4 November) and by 4.2–14.5MeV (23 November). Good agreement is generally obtained between observed and calculated absorption by the empirical flux-absorption relationship for threshold energy E0=10MeV. From the residuals one can argue that other factors (e.g. X-ray increases and geomagnetic disturbances) can contribute to the ionospheric absorption.Key words. Ionosphere (Polar Ionosphere, Particle precipitation) – Solar physics (Flares and mass ejections)

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A comparison between polynya area and associated ice production with mooring-based measurements of temperature, salinity and currents in the southwestern Ross Sea, Antarctica

Annals of Glaciology ◽

10.3189/172756411795931705 ◽

2011 ◽

Vol 52 (57) ◽

pp. 291-300 ◽

Cited By ~ 3

Author(s):

Stefan Kern ◽

Stefano Aliani

Keyword(s):

Ross Sea ◽

Time Lag ◽

Ice Formation ◽

Terra Nova Bay ◽

In Situ Observations ◽

Satellite Microwave ◽

Terra Nova ◽

Ice Production ◽

The Impact

AbstractWintertime (April–September) area estimates of the Terra Nova Bay polynya (TNBP), Antarctica, based on satellite microwave radiometry are compared with in situ observations of water salinity, temperature and currents at a mooring in Terra Nova Bay in 1996 and 1997. In 1996, polynya area anomalies and associated anomalies in polynya ice production are significantly correlated with salinity anomalies at the mooring. Salinity anomalies lag area and/or ice production anomalies by about 3 days. Up to 50% of the variability in the salinity at the mooring position can be explained by area and/or ice production anomalies in the TNBP for April–September 1996. This value increases to about 70% when considering shorter periods like April–June or May–July, but reduces to 30% later, for example July–September, together with a slight increase in time lag. In 1997, correlations are smaller, less significant and occur at a different time lag. Analysis of ocean currents at the mooring suggests that in 1996 conditions were more favourable than in 1997 for observing the impact of descending plumes of salt-enriched water formed in the polynya during ice formation on the water masses at the mooring depth.

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Source identification of atmospheric particle-bound metals at Terra Nova Bay, Antarctica

Environmental Chemistry ◽

10.1071/en14185 ◽

2015 ◽

Vol 12 (2) ◽

pp. 245 ◽

Cited By ~ 7

Author(s):

Andrea Bazzano ◽

Francesco Soggia ◽

Marco Grotti

Keyword(s):

Temporal Trends ◽

Austral Summer ◽

Anthropogenic Sources ◽

Anthropogenic Source ◽

Katabatic Wind ◽

High Concentration ◽

Sea Ice Extent ◽

Terra Nova Bay ◽

Terra Nova ◽

The Impact

Environmental context The atmosphere above Antarctica, the cleanest part of the Earth’s troposphere, serves as a valuable laboratory for studying natural atmospheric processes and for monitoring the impact of human activities on the global environment. Central to these studies is an understanding of long-range transport of pollutants to Antarctica, and distinguishing the relative contribution of natural and anthropogenic sources. We use chemical tracers and isotopic analysis to assess the origin of metals associated with atmospheric particulates in Antarctica. Abstract During the 2010–2011 austral summer, size-segregated aerosol samples were collected at a coastal Antarctic site (Terra Nova Bay, Victoria Land) and analysed for major and trace elements and lead isotopic composition, in order to provide a better understanding of the sources of metals and their transportation pathways towards Antarctica. Aerosol size fractionation was performed by a cascade impactor, able to collect aerosol particles of aerodynamic diameter 10–7.2, 7.2–3.0, 3.0–1.5, 1.5–0.95 and 0.95–0.49µm. It was found that Al, Co, Fe, Li, Mn, Rb, Y and V were mainly related to crustal inputs, whereas the marine contribution was significant for Li, Mg, Na and Rb. An additional anthropogenic source influencing the concentration of Cr, Cu, Mo and Pb was clearly demonstrated. The concentration of the elements associated to the crustal and marine inputs showed high values in the coarse mode (7.2–3.0µm), whereas the anthropogenic elements were also characterised by a high concentration in the finer (1.5–0.95µm) particles. The study of the temporal trends of the measured chemical markers along with the meteorological variables revealed that both the crustal and anthropogenic elements were related to the air masses carried by the katabatic wind from the inland, whereas the marine input appeared to be higher in January when the sea-ice extent was reduced. Finally, lead isotope ratios pointed out that the anthropogenic input was likely related to the polluted aerosols from South America and Australia, representing the predominant fraction (50–70%) of the lead measured in the samples.

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Low frequency geomagnetic field variations at Dome C (Antarctica)

Annales Geophysicae ◽

10.5194/angeo-21-923-2003 ◽

2003 ◽

Vol 21 (4) ◽

pp. 923-932 ◽

Cited By ~ 5

Author(s):

S. Lepidi ◽

L. Cafarella ◽

P. Francia ◽

A. Meloni ◽

P. Palangio ◽

...

Keyword(s):

Solar Wind ◽

Wind Speed ◽

Geomagnetic Field ◽

Solar Wind Speed ◽

Low Frequency ◽

Mhd Waves ◽

Polar Cap ◽

Ionospheric Currents ◽

Terra Nova Bay ◽

Terra Nova

Abstract. We conduct an analysis of the geomagnetic field variations recorded at the new Antarctic station Dome C, located very close to the geomagnetic pole, which has been operating for approximately one month during the 1999–2000 campaign. We also perform a comparison with simultaneous measurements at the Italian Antarctic station Terra Nova Bay, in order to investigate the spatial extension of the phenomena observed at very high latitude. Our results show that between the two stations the daily variation is similar and the fluctuations with f ~ 1 mHz are coherent, provided that in both cases the comparison is made between geographically oriented components, suggesting that ionospheric currents related to the geographic position, more than field-aligned currents, are responsible for the lowest frequency variations; conversely, higher frequency (Pc5) fluctuations are substantially decoupled between the two stations. We also found that at Dome C the fluctuation power in the 0.55–6.7 mHz frequency band is well related with the solar wind speed during the whole day and that at Terra Nova Bay the correlation is also high, except around local geomagnetic noon, when the station approaches the polar cusp. These results indicate that the solar wind speed control of the geomagnetic field fluctuation power is very strict in the polar cap and less important close to the polar cusp.Key words. Magnetospheric physics (MHD waves and instabilities; Polar cap phenomena; Solar wind-magnetosphere interactions)

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On solar protons and polar cap absorption: constraints on an empirical relationship

Annales Geophysicae ◽

10.5194/angeo-22-1133-2004 ◽

2004 ◽

Vol 22 (4) ◽

pp. 1133-1147 ◽

Cited By ~ 19

Author(s):

A. J. Kavanagh ◽

S. R. Marple ◽

F. Honary ◽

I. W. McCrea ◽

A. Senior

Keyword(s):

Empirical Relationship ◽

Cosmic Ray ◽

Solar Proton ◽

Proton Flux ◽

High Solar Activity ◽

Square Root ◽

Polar Cap ◽

Integral Flux ◽

Solar Proton Events ◽

The Relationship

Abstract. A large database of Solar Proton Events (SPE) from the period 1995 to 2001 is used to investigate the relationship between proton flux at geostationary orbit and Cosmic Noise Absorption (CNA) in the auroral zone. The effect of solar illumination on this relationship is studied in a statistical manner by deriving correlation coefficients of integral flux and absorption as a function of solar zenith angle limit, thus both an upper limit on the angle and the best correlated integral flux of protons are determined (energies in excess of 10MeV). By considering the correlation of various energy ranges (from the GOES 8 differential proton flux channels) with CNA the range of proton energies for which the relationship between flux and absorption is best defined is established (15 to 44MeV), thus confirming previous predictions about which proton energy ranges are most effective in giving rise to absorption during Polar Cap Absorption (PCA) events. An empirical relationship between the square root of the integral proton flux and the absorption, measured by the imaging riometer at Kilpisjärvi (IRIS), is determined and departures from linearity and possible causes are examined. Variations in spectral "hardness" and in collision frequency are demonstrated not to be significant causes of the observed departures from a linear relationship. Geomagnetic activity may be a significant factor in changing the relationship between the absorption and the square root of the integral proton flux, although it is concluded that the cause is likely to be more complex than a straightforward dependence on Kp. It is suggested that the most significant factor might be a bias in the absorption estimates imposed by the presence of Solar Radio Emission (SRE), which is not routinely measured at the operating frequency of IRIS, making its precise effect difficult to quantify. SRE is known to be most prevalent under conditions of high solar activity, such as those that might give rise to solar proton events. Key words. Ionosphere (particle precipitation; solar radiation and cosmic ray effects; polar ionosphere)

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Polarization pattern of low and mid-frequency magnetic pulsations in the polar cap: A comprehensive analysis at Terra Nova Bay (Antarctica)

Advances in Space Research ◽

10.1016/j.asr.2008.10.009 ◽

2009 ◽

Vol 43 (7) ◽

pp. 1135-1142 ◽

Cited By ~ 6

Author(s):

U. Villante ◽

P. Francia ◽

M. Vellante ◽

M. De Lauretis

Keyword(s):

Comprehensive Analysis ◽

Polarization Pattern ◽

Polar Cap ◽

Terra Nova Bay ◽

Magnetic Pulsations ◽

Terra Nova

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Predator–prey relationship between the nototheniid fish Trematomus bernacchii and the Antarctic scallop Adamussium colbecki at Terra Nova Bay (Ross Sea)

Antarctic Science ◽

10.1017/s0954102000000092 ◽

2000 ◽

Vol 12 (1) ◽

pp. 64-68 ◽

Cited By ~ 19

Author(s):

Marino Vacchi ◽

R. Cattaneo-Vietti ◽

M. Chiantore ◽

M. Dalu

Keyword(s):

Ross Sea ◽

Size Structure ◽

Medium Size ◽

Predator Prey ◽

Size Classes ◽

Terra Nova Bay ◽

Trematomus Bernacchii ◽

Terra Nova ◽

The Impact ◽

Adamussium Colbecki

Little information is available regarding predator-prey interactions in High-Antarctic coastal systems. In this study, the predation of Trematomus bernacchii (Pisces: Nototheniidae) on Adamussium colbecki (Mollusca: Pectinidae) is described and the related impact on the population structure of the mollusc is hypothesized. Fishes and scallops were collected during several expeditions between 1990/91 and 1997/98 summers, in nearshore waters at Terra Nova Bay (Antarctica). Adamussium colbecki was the main food item of T. bernacchii and an ontogenetic prey-size selection was observed. The predation was mainly on medium size classes of the scallop. These were lacking in the A. colbecki population sampled in the same period suggesting that the impact of fish-feeding on the size structure of the natural population of the mollusc may be substantial. Two size classes of the Adamussium population were not preyed on. Large adults avoid predation either because of the limits for mouth gape in the fish or by swimming avoidance capability, while smaller scallops may not be preyed upon because they are attached through byssus threads to very mobile large adults.

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