We present an update of the ‘key points’ from the Antarctic Climate Change and the Environment (ACCE) report that was published by the Scientific Committee on Antarctic Research (SCAR) in 2009. We summarise subsequent advances in knowledge concerning how the climates of the Antarctic and Southern Ocean have changed in the past, how they might change in the future, and examine the associated impacts on the marine and terrestrial biota. We also incorporate relevant material presented by SCAR to the Antarctic Treaty Consultative Meetings, and make use of emerging results that will form part of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report.

International audienceIn recent times it has become increasingly clear thatreleases of trace gases from human activity have a potentialfor causing change in the upper atmosphere. However,our knowledge of systematic changes and trends inthe temperature of the mesosphere and lower thermosphereis relatively limited compared to the Earths loweratmosphere, and not much effort has been made to synthesizethese results so far. In this article, a comprehensivereview of long-term trends in the temperature of the regionfrom 50 to 100 km is made on the basis of the availableup-to-date understanding of measurements and model calculations.An objective evaluation of the available datasets is attempted, and important uncertainly factors arediscussed. Some natural variability factors, which arelikely to play a role in modulating temperature trends,are also briefly touched upon. There are a growing numberof experimental results centered on, or consistent with,zero temperature trend in the mesopause region (80–100km). The most reliable data sets show no significant trendbut an uncertainty of at least 2 K/decade. On the otherhand, a majority of studies indicate negative trends inthe lower and middle mesosphere with an amplitude ofa few degrees (2–3 K) per decade. In tropical latitudesthe cooling trend increases in the upper mesosphere.The most recent general circulation models indicateincreased cooling closer to both poles in the middlemesosphere and a decrease in cooling toward the summerpole in the upper mesosphere. Quantitatively, thesimulated cooling trend in the middle mesosphere producedonly by CO₂ increase is usually below the observedlevel. However, including other greenhouse gasesand taking into account a “thermal shrinking” of theupper atmosphere result in a cooling of a few degreesper decade. This is close to the lower limit of the observednonzero trends. In the mesopause region, recentmodel simulations produce trends, usually below 1 K/decade,that appear to be consistent with most observationsin this regio

[1] This paper presents the first Antarctic meteor radar temperature estimates. These temperatures have been derived from meteor diffusion coefficients using two techniques: pressure model and temperature gradient model. The temperatures are compared with a temperature model derived using colocated OH spectrometer measurements and Northern Hemisphere rocket observations. Pressure model temperatures derived using rocketderived pressures show good agreement with the temperature model, while those derived using Mass Spectrometer and Incoherent Scatter (MSIS) and CIRA model pressures show good agreement in winter but poor agreement in summer. This confirms previous studies suggesting the unreliability of high-latitude CIRA pressures. The temperature gradient model temperatures show good agreement with the temperature model but show larger fluctuations than the pressure model temperatures. Meteor temperature estimates made during the Southern delta-Aquarids meteor shower are shown to be biased, suggesting that care should be taken in applying meteor temperature estimation during meteor showers. On the basis of our results we recommend the use of the pressure model technique at all sites, subject to determination of an appropriate pressure model.

[1] Pressure variations at 11 Antarctic sites and 7 Arctic sites have been examined and show significant correlations with a daily proxy for the output of the meteorological generators of the global atmospheric circuit. This proxy is derived from vertical electric field measurements made at Vostok on the Antarctic ice plateau. Taken with the finding of proportionate pressure variations correlated with atmospheric circuit changes owing to coupling with the interplanetary electric field, particularly for the Antarctic plateau (magnetic latitude > 83°) region, this provides experimental evidence that a small portion of the surface pressure variations are due to the influence of the global atmospheric circuit. The response to the interplanetary electric field is an example of Sun-weather coupling. To evaluate it, the daily average interplanetary magnetic field (IMF) east-west component (B y ) is used as a proxy for the north-south interplanetary electric field, which produces opposite ionospheric potential changes in the northern and southern polar caps. The correlation with IMF B y for the pressure variations for the Antarctic sites for a solar cycle (1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) is small (0.9% average covariance for the magnetic latitude > 83°sites) but significant (99.7% confidence level). The Arctic stations show a negative regression between pressure variations and IMF B y , a relationship expected if the linkage process operates by the atmospheric circuit, but it is only found when the interval is restricted to the peak of the sunspot cycle (1999)(2000)(2001)(2002).

Summary1. Decision support tools used for vegetation management require accurate information on the spatial array of different plant communities and a herbivore's grazing location. We tested the accuracy and precision of locations derived using the satellite navigation global positioning system (GPS). 2. Before May 2000, the accuracy and precision of GPS-derived locations were degraded by a process known as selective availability (SA); after May 2000, SA was disabled. In this study we investigated how to handle and improve the quality of data generated both when SA was enabled and when SA was disabled using relative GPS (rGPS). rGPS entails the post-processed correction of the roving GPS module with simultaneously acquired positional errors recorded at a known stationary reference location. 3. With SA enabled, GPS data were obtained at a fixed known location to obtain baseline information, and from a roving module that essentially mimicked surveying techniques or the movement of a free-ranging animal. The mean accuracy of GPS with SA enabled was 21 m for the fixed module and 25 m for the roving module. Use of rGPS and further manipulation of the data improved the mean accuracy of the data to 7 m for the fixed module and 10 m for the roving module. With SA disabled, data were similarly recorded from the fixed known location and resulted in a mean location accuracy of 5 m. The use of rGPS resulted in a significant improvement of this value to 3·6 m and precision measured by the 95% quantile was < 10 m. For mapping and wildlife tracking, such quality in terms of location accuracy and precision is unprecedented and demonstrates that rGPS may still be useful in many applications. 4. GPS enables the world-wide collection of accurate and precise location information at 1-second intervals. Furthermore, by programming the GPS receiver to overdetermine location by using information from all visible satellites, many of the limitations that arise in habitats or environments with a limited view of the sky may be overcome. 5. With SA now disabled, the potential use of GPS will increase. With further miniaturization, surveying of remote featureless landscapes or the tracking of crepuscular or far-ranging animals will become more accurate and more quantifiable than ever before.

Local temperature, wind speed, pressure, and solar wind–imposed influences on the vertical electric field observed at Vostok, Antarctica, are evaluated by multivariate analysis. Local meteorology can influence electric field measurements via local conductivity. The results are used to improve monthly diurnal averages of the electric field attributable to changes in the global convective storm contribution to the ionosphere-to-earth potential difference. Statistically significant average influences are found for temperature (−0.47 ± 0.13% V m−1 °C−1) and wind speed [2.1 ± 0.5% V m−1 (m s−1)−1]. Both associations are seasonally variable. After adjusting the electric field values to uniform meteorological conditions typical of the Antarctic plateau winter (−70°C, 4.4 m s−1, and 623 hPa), the sensitivity of the electric field to the solar wind external generator influence is found to be 0.80 ± 0.07 V m−1 kV−1. This compares with the sensitivity of 0.82 V m−1 kV−1 to the convective meteorology generator that is inferred assuming an average ionosphere-to-ground potential difference of 240 kV taken with the annual mean electric field value of 198 V m−1. Monthly means of the Vostok electric field corrected for the influence of both local meteorology and the solar wind show equinoctial (March and September) and July local maxima. The July mean electric field is greater than the December value by approximately 8%, consistent with a Northern Hemisphere summer maximum. The solar wind–imposed potential variations in the overhead ionosphere are evaluated for three models that fit satellite measurements of ionospheric potential changes to solar wind data. Correlations with Vostok electric field variations peak with a 23-min interpolated delay relative to solar wind changes at the magnetopause.

Abstract. An ensemble of space-borne and ground-based instruments has been used to evaluate the quality of the version 2.2 temperature retrievals from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS). The agreement of ACE-FTS temperatures with other sensors is typically better than 2 K in the stratosphere and upper troposphere and 5 K in the lower mesosphere. There is evidence of a systematic high bias (roughly 3-6 K) in the ACE-FTS temperatures in the mesosphere, and a possible systematic low bias (roughly 2 K) in ACE-FTS temperatures near 23 km. Some ACE-FTS temperature profiles exhibit unphysical oscillations, a problem fixed in preliminary comparisons with temperatures derived using the next version of the ACE-FTS retrieval software. Though these relatively large oscillations in temperature can be on the order of 10 K in the mesosphere, retrieved volume mixing ratio profiles typically vary by less than a percent or so. Statistical comparisons suggest these oscillations occur in about 10% of the retrieved profiles. Analysis from a set of coincident lidar measurements suggests that the random error in ACE-FTS version 2.2 temperatures has a lower limit of about ±2 K.

Temperature profiles from two satellite instruments – TIMED/SABER and Aura/MLS – have been used to calculate hydroxyl-layer equivalent temperatures for comparison with values measured from OH(6-2) emission lines observed by a ground-based spectrometer located at Davis Station, Antarctica (68° S, 78° E). The profile selection criteria – miss-distance <500 km from the ground station and solar zenith angles >97° – yielded a total of 2359 SABER profiles over 8 years (2002–2009) and 7407 MLS profiles over 5.5 years (2004–2009). The availability of simultaneous OH volume emission rate (VER) profiles from the SABER (OH-B channel) enabled an assessment of the impact of several different weighting functions in the calculation of OH-equivalent temperatures. The maximum difference between all derived hydroxyl layer equivalent temperatures was less than 3 K. Restricting the miss-distance and miss-time criteria showed little effect on the bias, suggesting that the OH layer is relatively uniform over the spatial and temporal scales considered. However, a significant trend was found in the bias between SABER and Davis OH of ~0.7 K/year over the 8-year period with SABER becoming warmer compared with the Davis OH temperatures. In contrast, Aura/MLS exhibited a cold bias of 9.9 &plusmn; 0.4 K compared with Davis OH, but importantly, the bias remained constant over the 2004–2009 year period examined. The difference in bias behaviour of the two satellites has significant implications for multi-annual and long-term studies using their data