Concluding remarks on the pre-instrumental period

This page is part of the topic Antarctic climate and environment history in the pre-instrumental period

This chapter has summarised our current understanding of Antarctic climate and environment history prior to the instrumental record, and the biological effects of climate and environmental change. Although the broad features of the climate and environmental history of Antarctica are being progressively documented, improvements can still be made in understanding the detailed sequence of events with better resolution both temporally (for instance, in the phasing of changes in Antarctic climate, environmental parameters and atmospheric composition) and spatially, particularly in near coastal regions. This calls for enhanced geographical coverage of high resolution records and a better understanding of climate dynamics.

Research priorities for the ice core community in Antarctica include collecting a 1.5 million year record of climate and greenhouse gases from Antarctica (spanning the time period where Earth’s climate shifted from 40,000 year to 100,000 year cycles); a 40,000 year bipolar network of records of climate forcing (to improve understanding of the detailed sequence of events across Termination 1, particularly at coastal sites representative of different oceanic basins), and a network of ice core climate and climate forcing records for the last two millennia (IPICS, 2008). These will help to progress understanding of the climate and biogeochemical cycle responses to climate forcings, the climate variability around Antarctica and its source areas. Similarly, and despite the strong correlation between CO₂ variations and Antarctic temperature, identifying the mechanisms involved in glacial-interglacial changes in greenhouse gas concentrations and their lags with Antarctic temperature is still a challenge for modellers (Köhler et al., 2005). In addition, for a better understanding of climate dynamics, new ice cores are also needed to improve the knowledge of Antarctic ice sheet dynamics over the past deglaciation. In particular, results from new ice cores from Detriot Plateau and James Ross Island in the Antarctic Peninsula region are eagerly anticipated as these are located in the fastest warming region of Antarctica.

For marine and terrestrial records the priority is to improve the geographical coverage and spatial resolution of the data so that the underlying links with climate forcing mechanisms emerge. A particular challenge is to constrain the timing of major climate events so that leads and lags may be identified. For example, records of climate optima in the marine and terrestrial environment in the mid to late Holocene are often out of phase and, with the exception of the Antarctic Peninsula (Bentley et al., 2009), little attention has been paid to identifying the mechanisms driving the different palaeoclimate patterns in various archives at a regional scale. Another example is the occurrence of a later Holocene climate optimum in the Ross Sea which is in phase with a marked cooling observed in ice cores from coastal and inland locations (Masson et al., 2000; Masson-Delmotte et al., 2004). These differences in the timing of warm events in different records, and in different regions, point to a number of mechanisms that we have yet to identify. Priority areas include coastal Antarctica, the Dronning Maud Land region, West Antarctica and specific regions of the Antarctic Peninsula. Here, modellers can also be of significant help in carrying out data model comparisons and providing sound theoretical frameworks within which to identify and answer the major questions

In terms of glacial history further work on the response of the ice sheet to climate change is required, particularly geological records of past ice sheet extent, including submarine surveys, and records of past relative sea level change. New biological evidence of floras that have survived through glacial cycles also challenges existing ice sheet models where most of the available habitats are covered at the LGM.

For past sea ice studies more marine sediment core data are needed to reconstruct past sea ice extent particularly in the Pacific sector of the Southern Ocean. Further detailed comparisons are required of marine sediment core-based and ice core-based sea ice reconstructions on a region by region basis. Sea ice is also a factor that remains poorly constrained in computer simulations of past and future climate change primarily because of this paucity of historical and palaeo records of sea ice extent.

The study of the response of biological communities in Antarctica and the Southern Ocean to historical and contemporary climate change, beyond the instrumental record, is still in its infancy, and nearly absent at smaller (microorganism to molecular) scales, yet this potentially offers many analogues with which to better understand the climate changes predicted to occur in the next 100 years. For example, on the Antarctic Peninsula, which is the fastest warming region of Antarctica, there is a pressing need for high resolution stratigraphic records that include evidence of changing species distributions. This region is likely to have been amongst the most responsive to climate changes of the past and already increasing temperatures in the last 50 years have resulted in the local expansion of population ranges of a number of plant and animal species, and the establishment (albeit with human assistance) of new species that appear not to have survived on the continent before. Similarly, climate impacts on biodiversity and production on land and in the ocean are still poorly constrained despite their wider economic consequences.