Special issue  

This research has been an investigation of two stalagmites from two caves in NW Madagascar to reconstruct the region's paleoenvironmental changes, and to understand the linkage of such changes to the dynamics of the ITCZ. Stable isotopes, mineralogy, and petrography suggest wetter climate conditions than today during the early and late Holocene, when the mean ITCZ was south, and drier during the mid-Holocene when the ITCZ was north.

A selection of climate models have been used to simulate both pre-industrial (1750 CE) and mid-Holocene (6000 years ago) conditions. This study presents an assessment of the temperature, rainfall and flow over Australasia from those climate models. The model data are compared with available proxy data reconstructions (e.g. tree rings) for 6000 years ago to identify whether the models are reliable. Places where there is both agreement and conflict are highlighted and investigated further.

The westerly winds determine weather patterns and exert an effect on carbon dioxide (CO₂) flux in and out of the Southern Ocean, an important sink for atmospheric CO₂. Our research reconstructs changes in the westerlies over the past 5000 years, using a marine sediment core record collected from the subantarctic Auckland Islands. Our results indicate an intensification of the westerlies around 1600 years ago, contemporaneous with other records from comparable latitudes across the Pacific Ocean.

Results from Lago Edita, central-western Patagonia (47° S), allow examination of the timing and direction of paleoclimate signals during the last glacial termination (T1) in southern midlatitudes. Cold and wet conditions prevailed during T1, terminated by warm pulses at 13 000 and 11 000 yr BP. Delayed warming, relative to sites along the Pacific coast, raises the possibility that residual ice masses in the Andes induced regional cooling along downwind sectors of central Patagonia during T1.

Little is known about the climate of southern Australia during the Last Glacial Maximum and deglaciation owing to sparse records for this region. We present the first high-resolution data, derived from speleothems that grew 23–5 ka. It appears that recharge to the Flinders Ranges was higher than today, particularly during 18.9–15.8 ka, argued to be due to the enhanced availability of tropical moisture. An abrupt shift to aridity is recorded at 15.8 ka, associated with restored westerly airflow.

Our study demonstrates that a source to sink analysis in the Gouritz catchment can be used to obtain valuable paleoclimatic information form the year-round rainfall zone. In combination with SST reconstructions these data are a valuable contribution to the discussion of Southern Hemisphere palaeoenvironments and climate variability (in particular atmosphere–ocean circulation and hydroclimate change) in the South African Holocene.

Thirty-six borehole temperature–depth profiles were analysed to reconstruct the ground surface temperature history (GSTH) of eastern Tasmania for the past 5 centuries. Temperature changes were greatest around the north-east coast and decreased towards midland Tasmania. Average GSTH reconstructed from Tasmanian boreholes shows temperature increases of about 1.2 ± 0.2 °C during the past 5 centuries.

The Southern Ocean plays a fundamental role in global climate but suffers from a dearth of observational data. As the Australasian Antarctic Expedition 2013–2014 we have developed the first annually resolved temperature record using trees from subantarctic southwest Pacific (52–54˚S) to extend the climate record back to 1870. With modelling we show today's high climate variability became established in the ~1940s and likely driven by a Rossby wave response originating from the tropical Pacific.

Latitudinal shifts in the Southern Ocean westerly wind jet could explain large observed changes in the glacial to interglacial ocean CO₂ inventory. However there is considerable disagreement in modelled deglacial-warming jet shifts. Here multi-model output is used to show that expansion of sea ice during the glacial period likely caused a slight poleward shift and intensification in the westerly wind jet. Issues with model representation of the winds caused much of the previous disagreement.

This paper highlights that small dunes (lunettes) formed on the eastern side of a lake in the Australian sub-tropics at the height of the last ice age (about 21,000 years ago) and in the early part of the current interglacial (9–6,000 years ago). This means that it was fairly wet at these times and also that there were strong westerly winds to form the dunes. Today strong westerly winds occur in winter, and we infer that the same was also true at those times, suggesting no change in circulation.

Geological evidence for past changes in glacier length provides a useful source of information about pre-historic climate change. We have used glacier modelling to show that air temperature reductions of −5 to −7 °C, relative to present, are required to simulate the glacial extent in the North Island, New Zealand, during the last ice age (approx. 20000 years ago). Our results provide data to assess climate model simulations, with the aim of determining the drivers of past natural climate change.