Radiocarbon variations from the southern hemisphere, 10,350-9700 cal BP

We have made AMS measurements on a series of 10-ring samples from a subfossil Huon pine log found in western Tasmania (42degreesS, 145degreesE). The results show a pronounced rise in Delta(14)C over the first 200 years, and a decrease over the following 160 years. Tree-ring width measurements indicate that this log (catalogue SRT-447) can be cross-dated with another subfossil log (SRT-416) for which a series of high-precision radiometric C-14 measurements have previously been made. When the two tree-ring series are thus aligned, SRT-447 is the older of the two logs, and there is a 139-year overlap. We then have a Huon pine floating chronology spanning 680 years, with C-14 measurements attached. The C-14 data sets agree well within the period of overlap indicated by the tree-rings. The C-14 variations from Huon pine show excellent agreement with those from German oak and pine for the period 10,350-9670 cal BP. Aligning the Huon pine C-14 Series with that from German oak and pine allows us to examine the inter-hemispheric offset in C-14 dates in the early Holocene. (C) 2004 Elsevier B.V. All rights reserved.

Ancient colour vision: Multiple opsin genes in the ancestral vertebrates

Molecular investigation of the origin of colour vision has discovered five visual pigment (opsin) genes, all of which are expressed in an agnathan (jawless) fish, the lamprey Geotria australis. Lampreys are extant representatives of an ancient group of vertebrates whose origins are thought to date back to at least the early Cambrian, approximately 540 million years ago [1.]. Phylogenetic analysis has identified the visual pigment opsin genes of G. australis as orthologues of the major classes of vertebrate opsin genes. Therefore, multiple opsin genes must have originated very early in vertebrate evolution, prior to the separation of the jawed and jawless vertebrate lineages, and thereby provided the genetic basis for colour vision in all vertebrate species. The southern hemisphere lamprey Geotria australis (Figure 1A,B) possesses a predominantly cone-based visual system designed for photopic (bright light) vision [2. S.P. Collin, I.C. Potter and C.R. Braekevelt, The ocular morphology of the southern hemisphere lamprey Geotria australis Gray, with special reference to optical specializations and the characterisation and phylogeny of photoreceptor types. Brain Behav. Evol. 54 (1999), pp. 96–111.2. and 3.]. Previous work identified multiple cone types suggesting that the potential for colour vision may have been present in the earliest members of this group. In order to trace the molecular evolution and origins of vertebrate colour vision, we have examined the genetic complement of visual pigment opsins in G. australis.

Levels and probable origin of predatory scarring on humpback whales (Megaptera novaeangliae) in east Australian waters

To investigate the incidence of non-lethal predation in Southern Hemisphere whales, more than 3400 fluke-identification photographs from resight histories of 1436 east Australian humpback whales were examined for evidence of predatory markings. Photographs were obtained from 1984 to 1996 at various locations along the east coast of Australia, from northern Queensland to southern New South Wales. Photographs were classified in terms of the level and type of scarring. The possible predator and whether the markings appeared fresh were also noted. In all, 17% of identified east Australian humpbacks possessed some form of predatory scarring, 57% of which was minor and 43% major. Almost all predatory scarring was consistent with that inflicted by killer whales. Only three whales demonstrated an increase in the level of predatory scarring after their first sightings. Two incidents of fresh scarring were recorded, and one fatal killer whale attack on a humpback whale calf was directly observed. The overall level of predatory scarring found in this study is comparable to those found in studies for Northern Hemisphere humpback whales. The low incidence of adult whales showing their first sign of predatory scarring after their initial sighting, and the small number possessing recent scarring, support the idea that east Australian humpback whales experience most predatory attacks early in life.

The Hi content of compact groups of galaxies

The Hi content of Hickson Compact Groups in the southern hemisphere is measured using data from the Hi Parkes All-Sky Survey (HIPASS), and dedicated observations using the narrow band filter on the Multibeam instrument on the Parkes telescope. The expected Hi mass of these groups was estimated using the luminosity, diameter, and morphological types of the member galaxies, calibrated from published data. Taking careful account of non-detection limits, the results show that the compact group population that has been detected by these observations has an Hi content similar to that of galaxies in the reference field sample. The upper limits for the undetected groups lie within the normal range; improvement of these limits will require a large increase in sensitivity.

Radiocarbon in tropical tree rings during the Little Ice Age

Cross-dated tree-ring cores (Pinus merkusii) from north-central Thailand, spanning AD 1620-1780, were used to investigate atmospheric C-14 for the tropics during the latter part of the Little Ice Age. In addition, a cross-dated section of Huon pine from western Tasmania, covering the same period of time, was investigated. A total of 16 pairs of decadal samples were extracted to alpha-cellulose for AMS C-14 analysis using the ANTARES facility at ANSTO. The C-14 results from Thailand follow the trend of the southern hemisphere, rather than that of the northern hemisphere. This is a surprising result, and we infer that atmospheric C-14 for north-central Thailand, at 17degrees N, was strongly influenced by the entrainment of southern hemisphere air parcels during the southwest Asian monsoon, when the Inter-Tropical Convergence Zone moves to the north of our sampling site. Such atmospheric transport and mixing are therefore considered to be one of the principal mechanisms for regional C-14 offsets. (C) 2004 Elsevier B.V. All rights reserved.

Review of tropospheric bomb C-14 data for carbon cycle modeling and age calibration purposes

Comprehensive published radiocarbon data from selected atmospheric records, tree rings, and recent organic matter were analyzed and grouped into 4 different zones (three for the Northern Hemisphere and one for the whole Southern Hemisphere). These C-14 data for the summer season of each hemisphere were employed to construct zonal, hemispheric, and global data sets for use in regional and global carbon model calculations including calibrating and comparing carbon cycle models. In addition, extended monthly atmospheric C-14 data sets for 4 different zones were compiled for age calibration purposes. This is the first time these data sets were constructed to facilitate the dating of recent organic material using the bomb C-14 curves. The distribution of bomb C-14 reflects the major zones of atmospheric circulation.

Integration of ice-core, marine and terrestrial records for the Australian Last Glacial Maximum and Termination: a contribution from the OZ INTIMATE group

The degree to which Southern Hemisphere climatic changes during the end of the last glacial period and early Holocene (30-8 ka) were influenced or initiated by events occurring in the high latitudes of the Northern Hemisphere is a complex issue. There is conflicting evidence for the degree of hemispheric 'teleconnection' and an unresolved debate as to the principle forcing mechanism(s). The available hypotheses are difficult to test robustly, however, because the few detailed palaeoclimatic records in the Southern Hemisphere are widely dispersed and lack duplication. Here we present climatic and environmental reconstructions from across Australia, a key region of the Southern Hemisphere because of the range of environments it covers and the potentially important role regional atmospheric and oceanic controls play in global climate change. We identify a general scheme of events for the end of the last glacial period and early Holocene but a detailed reconstruction proved problematic. Significant progress in climate quantification and geochronological control is now urgently required to robustly investigate change through this period. Copyright (c) 2006 John Wiley & Sons, Ltd.

Climatic variability in the southwest Pacific during the Last Termination (20-10 kyr BP)

The degree to which palaeoclimatic changes in the Southern Hemisphere co-varied with events in the high latitude Northern Hemisphere during the Last Termination is a contentious issue, with conflicting evidence for the degree of 'teleconnection' between different regions of the Southern Hemisphere. The available hypotheses are difficult to test robustly, however, because there are few detailed palaeoclimatic records in the Southern Hemisphere. Here we present climatic reconstructions from the southwestern Pacific, a key region in the Southern Hemisphere because of the potentially important role it plays in global climate change. The reconstructions for the period 20-10 kyr BP were obtained from five sites along a transect from southern New Zealand, through Australia to Indonesia, supported by 125 calibrated C-14 ages. Two periods of significant climatic change can be identified across the region at around 17 and 14.2 cal kyr BP, most probably associated with the onset of warming in the West Pacific Warm Pool and the collapse of Antarctic ice during Meltwater Pulse-1A, respectively. The severe geochronological constraints that inherently afflict age models based on radiocarbon dating and the lack of quantified climatic parameters make more detailed interpretations problematic, however. There is an urgent need to address the geochronological limitations, and to develop more precise and quantified estimates of the pronounced climate variations that clearly affected this region during the Last Termination. (c) 2005 Elsevier Ltd. All rights reserved.