Sean J. Fitzsimons

Regional insolation forcing of late Quaternary climate change in the Southern Hemisphere

In agreement with the Milankovitch orbital forcing hypothesis it is often assumed that glacial–interglacial climate transitions occurred synchronously in the Northern and Southern hemispheres of the Earth. It is difficult to test this assumption, because of the paucity of long, continuous climate records from the Southern Hemisphere that have not been dated by tuning them to the presumed Northern Hemisphere signals. Here we present an independently dated terrestrial pollen record from a peat bog on South Island, New Zealand, to investigate global and local factors in Southern Hemisphere climate changes during the last two glacial–interglacial cycles. Our record largely corroborates the Milankovitch model of orbital forcing but also exhibits some differences: in particular, an earlier onset and longer duration of the Last Glacial Maximum. Our results suggest that Southern Hemisphere insolation may have been responsible for these differences in timing. Our findings question the validity of applying orbital tuning to Southern Hemisphere records and suggest an alternative mechanism to the bipolar seesaw for generating interhemispheric asynchrony in climate change.

Climate sensitivity of a high-precipitation glacier in New Zealand

The sensitivity of glaciers to climatic change is key information in assessing the response and sea-level implications of projected future warming. New Zealand glaciers are important globally as an example of how maritime glaciers will contribute to sea-level rise. A spatially distributed energy- balance model is applied to Brewster Glacier, New Zealand, in order to calculate glacier mass balance, run-off and sensitivity to climate change. The model successfully simulates four annual mass-balance cycles. Close to half (52%) of the energy available for melt on the glacier is supplied by turbulent heat fluxes, with radiation less important, except during the winter. Model sensitivity to temperature change is one of the largest reported on Earth, at -2.0 m w.e. a -1 8C -1 . In contrast, a 50% change in precipitation is required to offset the mass-balance change resulting from a 18C temperature change. Meltwater run- off sensitivity is also very high, increasing 60% with a 18C warming. The extreme sensitivity of mass balance to temperature change suggests that significant ice loss will occur with even moderate climate warming.

Lake sediments record cycles of sediment flux driven by large earthquakes on the Alpine fault, New Zealand

Large earthquakes in mountain regions commonly trigger extensive landsliding and are important drivers of erosion, but the contribution of this landsliding to long-term erosion rates and seismic hazard remains poorly understood. Here we show that lake sediments record postseismic landscape response as a sequence of turbidites that can be used to quantify erosion related to large (moment magnitude, M w > 7.6) earthquakes on the Alpine fault, New Zealand. Alpine fault earthquakes caused a threefold increase in sediment flux over the ∼50 yr duration of each postseismic landscape response; this represents considerable delayed hazard following earthquake-induced strong ground motion. Earthquakes were responsible for 27% of the sediment flux from the lake catchment over the past 1100 yr, leading us to conclude that Alpine fault earthquakes are one of the most important drivers of erosion in the range front of the Southern Alps.

Abundance and Dynamics of Dissolved Organic Carbon in Glacier Systems

Abstract The biogeochemical cycling of organic carbon (OC) has important implications for aquatic system ecology because the abundance and molecular characteristics of OC influence contaminant transport and bioavailability, and determine its suitability as a substrate for microbial metabolism. There have been few studies of OC cycling in glacier systems and questions remain regarding the abundance, provenance, and biogeochemical transformations of OC in these environments. To address these questions, the abundance and fluorescence characteristics of dissolved organic carbon (DOC) were investigated at John Evans Glacier and Outre Glacier, Canada, and Victoria Upper Glacier, Antarctica. These systems are characterized by different thermal and hydrological regimes, and have different potential DOC sources. Where possible, samples of supraglacial runoff, glacier ice and basal ice, and subglacial meltwater were collected. The DOC concentration in each sample was measured (high-temperature combustion and non-dispersive IR detection), and emission and/or synchronous fluorescence spectroscopy were used to characterize the DOC from each environment. DOC exists in detectable quantities (0.06–46.6 ppm) in all of these glacier systems. The fluorescence characteristics of DOC vary between glaciers, between environments at the same glacier, and over time within a single environment. These results suggest that quality of available OC and glacier hydrological flow routing influence the characteristics of DOC, and that microbial cycling of OC may be active in glacier systems.

Characterization of dissolved organic matter (DOM) from glacial environments using total fluorescence spectroscopy and parallel factor analysis.

Abstract Aquatic dissolved organic matter (DOM) is a major reservoir of reduced organic carbon and has a significant influence on heterotrophic biological productivity and water quality in marine and freshwater environments. Although the forms and transformations of DOM in temperate aquatic and soil environments have been studied extensively, this is not the case for glacial environments. In this study, fluorescent excitation–emission matrices (EEMs), parallel factor analysis (PARAFAC) and cluster analysis were used to characterize the fluorescing components of DOM in ice and water samples from supraglacial, englacial, subglacial and proglacial environments of seven glaciers in the Canadian Arctic, Norway and Antarctica. At least five significant fluorescent DOM fractions were identified, which accounted for 98.2% of the variance in the dataset. These included four protein-like components and one humic-like component. The predominantly proteinaceous character of DOM from these glaciers is very different from the more humic character of DOM described previously from lacustrine, fluvial, estuarine and marine environments. DOM from the sampled glaciers is broadly similar in character despite their geographically distinct locations, different thermal regimes and inter- and intra-site differences in potential organic matter sources. Glacier ice samples had a relatively low ratio of humic-like :protein-like fluorescence while meltwater samples had a higher ratio.

Late cainozoic glaciation in western tasmania, Australia

Abstract Four major Quaternary glaciations, with associated interglaciations and interstadials, have been identified in Tasmania, for which some chronological cotrol is given by radiocarbon and amino-acid assays, pollen analysis and relative weathering characteristics. The glaciations are known as the Margaret, Henty, Moore and Linda. The Margaret Glaciations has two clear stadial intervals (Isotope Stages 4 and 2), separated by the Tullabardine Interstadial dated at ca. 50-25 ka BP. An interglaciation corresponding to Isotope Stage 5 (Pieman Interglaciation) is characterised by sediments containing a pollen assemblage of a temperate rain forest. Weathered glacial deposits lying beneath the Pieman sediments are inferred to be those of the Penultimate Glaciation; three stadial moraines are identified. A preceding interglaciation (Langdon) contains wood that yielded an amino-acid ratio equivalent to the age of marine Isotope Stage 7. The following Moore Glaciation had three stadial intervals, two of which are separated by a clear interstadial (Baxter) with organic sediments that have amino-acid ‘ages’ equivalent to Isotope Stage 10; the non-glacial sediments have a DRM of normal polarity and are inferred to be of Mid-Quaternary age. The oldest interglaciation (Regency) is identified from organic-rich sediments (pollen assemblage of a temperate rain forest) overlying intensely weathered glacial deposits that have a DRM with reversed polarity (i.e. > 730 ka). The Linda Glaciation is the most extensive of all in Tasmania; although dating is uncertain, it has been assigned tentatively to the Early Quaternary.

Ice-marginal depositional processes in a polar maritime environment, Vestfold Hills, Antarctica

Fig. 1. Location map of Vestfold Hills showing the position of the edge of the continental ice sheet, Sersdal Glacier, and the position of the three localities examined in detail. Vestfold Hills are a small ice-free area in Princess Elizabeth Land, Antarctica (Fig. 1). The edge of the continental ice sheet runs from north to south and the southern limit of the ice-free area is formed by Sorsdal Glacier, which is the major outlet glacier of the area and forms a small ice shelf (Fig. 1). The hills consist of a complex low-relief topography composed of valleys at and below sea-level and ridges up to 158m in altitude. Glacial sediments and land forms are absent from most of the ice-free area. They are concentrated in ice-marginal areas where most moraines are ice-

The formation and hydrological significance of cryoconite holes

Cryoconite holes have been discussed in the literature since Nordenskiölds 1870 crossing of Greenland. They are found in high latitude and high alpine glaciers where sediment is transported onto the glacier surface, causing differential ablation. While studied periodically since 1870, in the last decade there has been a resurgence of interest in understanding the hydrology, biogeochemistry and ecology of cryoconite holes, and so it is timely to take stock of the current state of understanding, and to compile a roadmap for future endeavours. This paper combines past findings into a systems framework so as to identify the key integrative findings of cryoconite holes as single entities, and as a part of the wider glacier system.

Molecular characterization of dissolved organic matter in glacial ice: coupling natural abundance 1H NMR and fluorescence spectroscopy.

Glaciers and ice sheets are the second largest freshwater reservoir in the global hydrologic cycle, and the onset of global climate warming has necessitated an assessment of their contributions to sea-level rise and the potential release of nutrients to nearby aquatic environments. In particular, the release of dissolved organic matter (DOM) from glacier melt could stimulate microbial activity in both glacial ecosystems and adjacent watersheds, but this would largely depend on the composition of the material released. Using fluorescence and (1)H NMR spectroscopy, we characterize DOM at its natural abundance in unaltered samples from a number of glaciers that differ in geographic location, thermal regime, and sample depth. Parallel factor analysis (PARAFAC) modeling of DOM fluorophores identifies components in the ice that are predominantly proteinaceous in character, while (1)H NMR spectroscopy reveals a mixture of small molecules that likely originate from native microbes. Spectrofluorescence also reveals a terrestrial contribution that was below the detection limits of NMR; however, (1)H nuclei from levoglucosan was identified in Arctic glacier ice samples. This study suggests that the bulk of the DOM from these glaciers is a mixture of biologically labile molecules derived from microbes.

Geology and Geomorphology of the European Alps and the Southern Alps of New Zealand

Abstract The European Alps (Alps) and Southern Alps of New Zealand (Southern Alps) are both high mountain ranges formed by the collision of tectonic plates. The Alps resulted from collision of the African and European Plates, which produced complex lithological and structural patterns associated with the development of a series of overthrusted nappes. In contrast, the plate margin deformation that created the Southern Alps produced a relatively simple structural and lithological pattern dominated by a single right lateral oblique slip fault zone known as the Alpine Fault. Strong contrasts are also apparent in the contemporary rates of landscape development. The Alps currently experience modest rates of uplift and denudation because deformation along the plate boundary has slowed. High rates of compressional strain along the Alpine Fault in New Zealand result in very high rates of uplift. These processes and the position of the mountain range across the prevailing atmospheric westerly circulation system result in exceptionally high rates of denudation. Although there are strong contrasts in the lithology and structure of the Alps and Southern Alps, both experienced the growth and decay of expanded valley and piedmont glaciers during the Quaternary. The impact of multiple Quaternary ice advances has left a strong imprint on the landscapes. Both mountain ranges have particularly well-developed, over-deepened troughs and widespread glacial sediments and landforms, which heavily influence modern geomorphic processes and land use. Today numerous glaciers in both regions show strong reactions to global warming since the end of the Little Ice Age.