The characteristics of, and the mechanisms causing, multi-decadal variability are currently receiving much attention. This undertaking is particularly challenging in the sub-Antarctic region because of the paucity of data, and the complexity of the governing physical processes.

In this paper we report on aspects of high-southern-latitude variability which appear in the European Centre for Medium-range Weather Forecasts twice-daily analyses for the period 1 January 1980 to 31 August 1996 and in the results of global climate model experiments. We show that the number of cyclone positions in the 50-70°S latitude band exhibits considerable interannual variability, as well as changes on longer time-scales. The seasonal distribution of cyclones is linked with the “semi-annual oscillation". We show that the variability of this phenomenon in a 1000 year run of the GFDL coupled model shows “red” characteristics fand on decadal time-scales is similar to that displayed in the available observationsi. The interaction with the ocean and sea ice is siressed as an important factor in determining the nature of climate variability in sub-Antarctic latitudes.

The glaciers of the Antarctic Peninsula are believed to react rapidly to climatic fluctuations. Thus it is of great interest to find methods for monitoring regional climate variability in this region, Two small glaciers on the Antarctic Peninsula were chosen to monitor the accumulation and ablation pattern of the snow cover in respect to climate variations. During two summer seasons, synthetic aperture radar pulse-repetition interval images from the European ERS-1 active microwave satellite instrument were collected. Simultaneously, micro-meteorological measurements with simple automatic weather stations were carried out at three locations on the glaciers. Energy available for snowmelt was computed using the bulk transfer equations. Incorporating a digital terrain model and a model for shortwave irradiance, estimates of the energy available for melt were then calculated for the entire glaciers. The resulting time series of spatially distributed information on available energy can be used to separate periods and areas with snow-melt from periods and areas with completely frozen snow cover. The same separation can be achieved from the ERS-1 imagery. Integrating both the remote-sensing technique and the ground observations, it may be possible to establish a combined method to monitor the effects of weather patterns on a seasonal basis.

Air temperatures at the Marambio (MAR), Esperanza (ESP) and Matienzo (MAT) stations have been analyzed to investigate recent climate change on the eastern part of the Antarctic Peninsula. They are compared with data from the Oreadas station on the South Orkney Islands, the longest record available in Antarctica, and from the Faraday (FAR) station on the western coast of the Peninsula. Though the interannual variability is comparatively high and the stations are located in different climatic regimes, a pronounced warming trend shows up in all records. At MAR a temperature increase of 1.5°C has been observed since the beginning of the record in 1971. This is of similar magnitude to the increase at FAR on the west coast, which was 2.5°C for the longer period since 1945. The steady retreat and collapse of the northern Larsen Ice Shelf (LIS) coincided with this warming trend. of particular importance for the ice-shelf mass balance in this region are the summer temperatures which show a statistically significant warming trend at MAR and ESP. The representativity of the summer temperatures of MAR for northern LIS is confirmed by intercomparison with the parallel measurements at MAT which is located on the ice shelf.

Comparison of aerial photos shows that the ice cliff in Marian Cove, Maxwell Bay, southwestern King George Island, retreated approximately 250 m between 1956 and 1986, but advanced about 40 m between December 1986 and January 1989. The advance in the late 1980s seems to be related to the cold austral winters of 1986-88. A topographic survey in January 1994 revealed that the ice cliff in Marian Cove had again retreated around 270 m since January 1989; approximately the same as from December 1956 to December 1986. in Potter Cove, the ice cliff retreated approximately 400 m from 1956-89. The more pronounced retreat here may be attributable to shallower water depths (<30m). These ice cliffs retreats are discussed as a possible consequence of recent regional warming.

Aerial photography has been used as a mapping tool in the Antarctic Peninsula region sinre the late 1920s. Following pioneering work by Wilkins in 1928, Ellsworth in 1934 and the British Graham Land Expedition in 1934-37, the Falkland Islands and Dependencies Aerial Survey Expedition carried out extensive aerial photography during the period 1955-57. Since then, many other aerial surveys have been carried out, and the result is an archive of aerial photography that, for some localities, spans 40 years. The production of maps both from different generations of photographs and satellite images has revealed many changes in the extent of ice cover with time. For example, changes in ice shelves such as the Wordie Ice Shelf, Larsen Ice Shelf and Müller Ice Shelf, are well recorded, and the termini of some glaciers have retreated. However, the most pervasive change is the consistent decline in the extent of small bodies of snow and ice. This paper shows how perennial snow or ice cover has decreased in the northern Marguerite Bay area, at 68°S. The correlation of the change with elevation and with climate records from Adelaide and Rothera research stations in the Antarctic Peninsula region is examined.

Ice-front change may well be a sensitive indicator of regional climate change. We have studied the western Oates Coast from Cape Kinsey (158°50' E, 69°19' S) to Cape Hudson (153°45' Ε, 68°20' S) and the entire George V Coast, from Cape Hudson to Point Alden (142°02' E, 66°48' S). The glaciers here drain part of the Dome Charlie and Talos Dome areas (640 000 km2). A comparison between various documents, dated several years apart, has allowed an estimate of the surficial ice discharge, the ice-front fluctuation and the iceberg-calving flux during the last 50 years. The ice-front discharge of the studied coast has been estimated at about 90 ± 12 km3a−1 in 1989-91, 8.5 km3a−1 for western Oates Coast and 82 km3a−1 for George V Coast. From 1962-63 to 1973-74 the floating glaciers underwent a net reduction that continued from 1973-74 to 1989-91. On the other hand, from 1989-91 to 1996 the area of floating glaciers increased. Ninnis Glacier Tongue and the western part of Cook Ice Shelf underwent a significant retreat after 1980 and 1947, respectively. Satellite-image analysis of large icebergs has provided information about ice-ocean interaction and the existence of an “iceberg trap” along George V Coast. A first estimate of the mass balance of the drainage basin of Mertz and Ninnis Glaciers shows a value close to zero or slightly negative.

The association of the European “Little Ice Age” (1550- 1850; Lamb, 1982) with a period of significantly reduced solar activity (Eddy, 1976) suggests a significant mechanism of climate variation remains to be determined. Recent optical observations of connections between the tops of thunderstorm systems and altitudes of 70-90 km (Sentman and Wescott, 1996) demonstrate a linkage between the troposphere and the lower reaches of the ionosphere. If thunderstorm development is affecled by its electrical environment, then solar modulation of the geoelectric field provides a viable solar-variability-climate mechanism (see, e.g., Tinsley 1996). The high, dry Antarctic plateau provides an ideal site for demonstrating that solar variability can influence the geoelectric field. in this paper, we present evidence that the geoelectric field at Vostok is modulated by the duskward component of the Interplanetary Magnetic Field (IMF By) when Vostok rotates under the region magnetically linked to the dayside interaction region between the solar wind and the Earth's magnetic field.

Specific parameters determined from continental ice sheet or glacier cores can be used to reconstruct former climate. Tο use this scientific resource effectively, an information system is needed which guarantees consistent long-term data storage and provides easy access. Such a system, to archive any data of paleoclimatic relevance, together with the related metadata, raw data and evaluated paleoclimatic data, is presented. It is based on a relational database and provides standardized import and export routines, easy access with uniform retrieval functions and tools for visualizing the data. The network is designed as a client-server system, providing access through the Internet with proprietary client software including a high functionality or read-only access to published data via the World Wide Web (www.pangaea.de).

The Southern Ocean is the largest of the high-nutrient, low-chlorophyll (HNLC) regions of the world ocean. Phytoplankton production fails to utilise completely the pool of inorganic nutrients in the euphotic zone, giving rise to low phytoplankton bio-mass and leaving relatively high summer nutrient concentrations. This enigma is of considerable significance for our understanding of the role of the oceans in the global carbon cycle. Various limiting factors have been considered: low light, low temperature, absence of necessary trace elements, grazing pressure and other means of biomass removal.

The dynamics of nitrogen uptake by phytoplankton are of particular importance. Classically, nitrate mixed into the surface layer during winter provides the nitrogen pool for growth in the spring bloom. Some organic material is exported to depth, whilst the remainder is recycled, providing ammonium and other reduced species as nitrogenous substrates for growth during the remainder of the season. The oxidation state of the inorganic nitrogen supply thus identifies new and recycled carbon fixation. Whilst this is convenient “shorthand” for the nitrogen nutrition of carbon export in much of the ocean, it is an inappropriate model for the Southern Ocean. Here, nitrate and ammonium use are simultaneous, and nitrate is never exhausted by the annual phytoplankton production.

We speculate that a range of environmental factors combine to make the large pool of nitrate partially inaccessible to phytoplankton. in addition to the documented effects of low iron availability and high ammonium concentrations, the low temperatures characteristic of the Southern Ocean may decrease nitrate availability because of the increased energetic overheads in its uptake and reduction. This in turn makes ammonium an important nitrogenous substrate, and its production by zooplankton and heterotrophic microorganisms is an important component of the plankton nitrogen cycle. There is some evidence that ammonium production by large grazing animals may stimulate phytoplankton growth. Microbial removal of nitrogen from sedimenting phytoplankton cells may result in local decoupling between the carbon and nitrogen cycles, allowing some reduced nitrogen to remain in the euphotic zone whilst carbon is exported to depth.

The polar mesopause region (80-100 km) is the coldest region of the Earth's atmosphere and is expected to be sensitive to global change. Reported increases in observations of polar mesospheric clouds over the last 100 years have been postulated to be related to decreased temperatures (associated with tropospheric warming) and increased water vapour at mesospheric altitudes (a result of increased methane concentrations in the troposphere). The temperature of this region can be monitored by spectroscopic techniques utilising hydroxyl (OH) emissions which originate near 87 km. The Australian Antarctic Division, Atmospheric and Space Physics group has been analyzing OH (6-2) band spectra recorded with a Czerny—Turner scanning spectrometer at Davis Station, Antarctica (68.6° S, 78.0° E) to optimise temperature determinations for climate change studies. A number of difficulties were encountered, some of which have been overcome and all of which can be overcome. The mid-winter average temperature of the OH layer for May-July 1990 has been measured as 224 ±2 K. The equivalent value for 1996 is 215±2 K. Possible reasons for the difference are discussed.

Changes in the lead concentration in Antarctic snow over the past 30 years are considered as a response of the environment to a well-documented environmental change (decrease of lead emissions into the atmosphere). New data confirm the recent decreasing trend of lead concentration in snow as revealed by previous studies. Furthermore, comparing changes in the lead concentration in Antarctic snow layers with lead emissions from different anthropic sources, we can hypothesise that under present-day climatic conditions, lead-enriched aerosols reaching the Atlantic and Pacific sectors of East Antarctica originate mainly in South America and Australia, respectively.

The chemical (Na+, K+, Mg2+, Ca2+, CH3SO3− (MSA), Cl− , NO3− , SO42-) and isotopic (δl8O) composition of snow and firn samples from Campbell Glacier, northern Victoria Land, Antarctica, was studied to evaluate the accumulation rate of snow and to investigate the chemical contribution from some emission sources (marine biogenic activity, sea and crust). During the 1994-95 Italian Antarctic Expedition, snow and firn were collected from snow pits and from cores obtained from drilling at three sites (A: 74°41'S, 164°30' E; B: 74°15' S, 164° '04' E; C: 73°45' S, 163°20' E), located ai 50 m (on the floating glacier tongue), 800 m and 1580 m a.s.l., respectively.

The mean concentration of sea salt decreased with increasing distance from the coast and with altitude. Generally, the Na+/K+ and Na+/Ca2+ ratios were much lower than the bulk sea-water ratios at sites B and C. The MSA showed mean concentrations (0.27 and 0.17 ¿teq 1 at sites B and C, respectively) consistent with data obtained from other Antarctic sites. The mean concentrations of NO3 ranged from 2.1 μeq 1−1 (site A) to 0.97 μeq1 1 (site C).The mean nss (non-sea-salt) SO42-/SO42- ratio was -0.055,0.54 and 0.42 at sites A, B and C, respectively. Moreover, the relationship between a2+, nssCa2+, SO42- and nssSO4 was quite different at sites B and C. in order to expla in the relationships between the elements and compounds studied at these sites, chemical fractionation and/or reactions inside air masses and différent origin of the air masses at the two sites should be considered.

A comparison of the isotopic and chemical profiles was carried out in order to provide a more reliable chronological scale. The chemical and δ18O seasonal variations recorded along the firn cores from the upper site of Campbell Glacier seem to be fairly homogeneous. This made it possible to identify many annual cycles (14-18 years for the 7 m firn core). Using the measured density values, the accumulation rale was also calculated for lower and upper Campbell Glacier. It did not appear to differ between the two sites (150-170 kg m −2a−1 at site B and 140-180 kg m−2a−1at site C) and is in keeping with rates calculated previously for the same area.

One of the unusual features of Lakes Fryxell and Hnare in Taylor Valley, southern Victoria Land, Antarctica, is their perennial ice cover. This ice cover limits gas exchange between the atmosphere and the lake water, and causesa very stable stratification of the lakes. We analyzed a series of water samples from profiles of these lakes and their tributaries for δ13C of the dissolved inorganic carbon (DIC) in order to qualify the carbon flux from the streams into the lakes, and to investigate the carbon cycling with in the lakes. Isotopic values in the uppermost waters (δ13C = +l.3‰ to 5.3‰ in Lake Hoare, +0.4‰ to +3.0‰ in Lake Fryxell) are close to the carbon-isotope values encountered in the streams feeding Lake Fryxell, but distinctively heavier than in streams feeding Lake Hoare (δ13C= — 2.3%n to 1.4%). These ratios are much heavier than ratios found in the moat that forms around the lakes injanuary February (δC = -10.1%). in the oxic photic zones of the lakes, photosynthesis clearly influences the isotopic composition, with layers of high productivity having enriched carbon-isotope signatures δ13C= +2.7‰ to +6.1‰). in both lakes, the isotopic values become lighter with depth, reaching minima of 3.2‰ and 4.0% in Lakes Fryxell and Hoare, respectively. These minima are caused by the microbial remineralization of isotopically light organic carbon. We present DIC flux calculations that help to interpret the isotopic distribution. For example, in Lake Hoare the higher utilization of CO2aq, and a substantially smaller inflow of CO2 from streams cause the heavier observed isotopic ratios. Differences in the hydrology and stream morphologies of the tributaries also greatly influence the carbon budgets of the basins.

Lakes are a major feature of Arctic and Antarctic landscapes and are likely to be sensitive indicators ofclimate change. New bio-optical technologies for in situ measurements (e.g. UV-profiling) and remote sensing (e.g. light detection and ranging) now offer a suite of options for long-term monitoring at these sites. Certain properties of high-latitude lakes are highly responsive to changes in climate forcing and could be targeted within a monitoring strategy based on optical properties; these include lake levels, lake-ice dynamics, phytoplankton biomass and chromophoric dissolved organic matter (CDOM). High-latitude lakes are optically sensitive to changes in CDOM export from their surrounding catchments that could result from climate effects on hydrology and vegetation. Using a new model based on biologically weighted transparency, we show that a 20% change in GDOM concentration (as measured by dissolved organic carbon) can have a much greater effect on UV inhibition of phytoplankton than a similar percentage change in stratospheric ozone. Much of this effect is due to UV-A, because the reduced photodamaging effect per unit energy (i.e. low biological weighting) in this waveband is offset by its higher incident flux at the lake surface relative to UV-B and its deeper penetration into the water column. These transparency calculations also show that small changes in CDOM in polar lakes will have a large effect on underwater light availability for photosynthesis. The spectral absorption and fluorescence properties of CDOM lend themselves to a variety of optical monitoring approaches. Future research on the paleo-optics of GDOM will allow the interpretation of current optical trends in high-latitude lakes relative to the scales of natural variability in the past.

Eight sediment gravity cores, collected from the joides and Drygalski basins, were analysed in order to understand late Pleistocene-Holocene biogenic flux changes in the Ross Sea, driven by paleoenvironmental changes. Core lithologies and magnetic-susceptibility depth profiles were used for core logging and stratigraphic correlation. Nineteen AMS radiocarbon dates of bulk organic matter were used to set chronological constraints and calculate sediment accumulation rates. These rates, which vary from 1.4-38 cm ka−1. were used to obtain the burial fluxes of biogenic components. The highest fluxes occur in the deepest parts of the basins (TOC, 0.05-0.2 g cm −2 ka−1; biogenic silica, 1.5-5 g cm−1 ka−1), where as topographic highs show the lowest values (TOC, 0.01-0.1 g cm−2 ka−1 ; biogenic silica, 0.1-1.4 g cm−2 ka−1). Dramatic changes in both physical properties and fluxes record the establishment of open marine-sedimentation conditions which occurred first in the joides basin and then, with a delay of ca. 6000 years, in the Drygalski basin. Both TOC and biogenic-silica fluxes increase through the Holocene, though slightly differently. The high fluxes of both 10Be and biogenic Ba suggest that sediment accumulation at basin sites is strongly influenced by lateral transport.