glacier sensitivity to changes in climate – past and future
TRANSCRIPT
Abstracts / Quaternary International 279-280 (2012) 346–461418
POST-GLACIAL SPATIAL AND TEMPORAL PATTERNS OF PEATLANDINITIATION AND FORMATION PROCESSES OVER THE BOREAL NORTHERNEUROPE AND NORTH-AMERICA
Meri Ruppel. University of Helsinki/Department of Environmental, FinlandE-mail address: [email protected]
Peatlands are important ecosystems in the northern hemisphere wherethey cover vast areas, in some parts even two thirds of the land area. Theirrole in global biogeochemical processes is acknowledged and, accordingly,increasing interest to understand peatland dynamics - past, modern andfuture - is rising. Chronological and geographical data of peatland initiationhas, however, been scattered, hampering the establishment of a reliableview of post glacial spatio-temporal peatland development patterns. Herewe present, for the first time, a comprehensive broad-scale account of theinitiation and development histories of peatlands in boreal northernEurope and North-America. We used a data set of ca. 1500 basal peat agesfrom ca. 700 peatlands and literature-based sediment type interpretationsto investigate peatland formation pathways. This large data set provides anextensive spatio-temporal viewof the peatland formation processes duringthe Holocene. Based on the current data set the prevailing conception ofthe relative proportions of different initiation processes will change. Forinstance, in northern Europe and in North-America, peatland formationthrough lake infilling has been more common (ca. 30 %), than previouslyestimated. Moreover, the data set suggests that there does not exist anyexplicit link between any peatland formation process and climate,although paludification and subsequent lateral expansion of peatlandshave been slightly more intensive during wet climate phases. It also has tobe kept in mind that the gathered data may contain many error sourcesrelated to e.g. chronological control or identification of the sediment typeunderlying the basal peat. Nevertheless, this novel data set shows that inthe past all peatland formation pathways widely co-occurred, whichinformation can set a challenge for the peatland modeling community.
GLACIER SENSITIVITY TO CHANGES IN CLIMATE – PAST AND FUTURE
Summer Rupper. Brigham Young University, United StatesE-mail address: [email protected]
A suite of general circulation model (GCM) simulations and a glacierequilibrium line altitude (ELA) model are used to test the sensitivity of theglaciers of High Asia to simulated climate changes at the Last GlacialMaximum (LGM), mid-Holocene (6 ka), and future climate scenarios(2xCO2). Both intermodel differences as well as comparisons to recent andreconstructed glacier changes highlight regions where model uncertaintyis greatest, and provide a guide to focus field research where paleoclimateproxies and glacial histories are crucial in order to further constrain GCMs.In particular, the southeastern Himalaya is a region where intermodelvariability is extremely high, yet few paleoclimate proxies and glacierstudies are available to help constrain the models. This is an examplewhere numerical modelling efforts can strongly inform fieldwork. Inaddition, the suite of model simulations provides a test of glacier sensi-tivity to changes in boundary conditions. The results of this study highlighttemperature changes as being the most important influence on glacier ELAfor much of Central Asia and for all climate scenarios – past and future.However, this sensitivity is strongly dependent upon whether ablation isdominated by melt or sublimation. The ablation regime changes asboundary conditions change, therefore the glacier sensitivity to changes inclimate forcings in any given region is not stationary in time. These resultssuggest that glacier sensitivity determined for modern climatic conditionsmay not be applicable to past climates or future climate scenarios.
AN INTEGRATED APPROACH TO A MULTI-PROXY CLIMATE RECONSTRUCTION FROM LAMANAI, BELIZE, CENTRAL AMERICA
Elizabeth Rushton. University of Nottingham, United KingdomE-mail address: [email protected]
Lamanai, northern Belize (formally British Honduras), is a site of climaticvariability, ecological diversity and Mayan occupation. European colonial
involvement in the region encompasses both Spanish and British interestsand is complex. Belize forms part of the Yucatán Peninsula, a region thathas been the subject of much research due to the possible link betweenclimatic variation and associated shifts in the Maya culture and pop-ulations. Archaeological, paleolimnological and palynological data setsextend from 1500 BC to AD 1500 and show that Lamanai has beencontinuously occupied throughout a period of apparent ‘collapse’ dis-cussed in other research in the wider Yucatán region, and was occupied atthe time of the first European contact. However, there is little land-use andclimate change data from the site; or northern Belize in general, since AD1500. Exploration of documentary and instrumental sources in conjunc-tion with natural proxy data already available afford insight into therelative environmental impacts of pre- and post conquest societies in thisregion, contributing to debates surrounding the environmental impacts ofthe native population of the Americas prior to 1492, and to a widerunderstanding of human and climatic interaction in this part of Meso-america. Documentary sources to be consulted include those resultingfrom British involvement in Belize (ca. 1770s-1980s) e.g. maps, Governor'sreports and correspondence, shipping returns and blue book statistics.Archives of various missionary societies working in the region during the19th century including correspondence from those working in Belize willalso be exploited to extract direct and indirect references to local climateinformation This research seeks to highlight how instrumental, historicaland natural proxies from both local and regional scales and high and lowresolutions can be combined to provide the most complete and integratedclimate chronology possible.
ENHANCING THE CHRONOLOGY OF ARCHAEOLOGICAL SEQUENCES INCYRENAICA, NORTHERN LIBYA, USING SMALL ALIQUOT AND SINGLEGRAIN OPTICALLY STIMULATED LUMINESCENCE (OSL) DATING OFFINE SAND
Natalie Russell. Royal Holloway, University of London, United KingdomE-mail address: [email protected]
The internationally significant archaeological sequences and climaticrecords preserved in the landscape surrounding the Haua Fteah site in theCyrenaican region of Northern Libya contain an abundance of climaticproxies. While the chronology for these sequences is at present poorlyunderstood, these records offer the opportunity to further our under-standing of the local occupation sequence, and its relationship to the longterm environmental and human history of the southern Mediterraneanregion. This study reports the results of Optically Stimulated Luminescence(OSL) dating of fine sand-sized quartz from the Haua Fteah andsurrounding region. Fine sands (60-125 mm) were used due to the paucityof coarser grainedmaterial in all samples. Luminescence properties of eachsample were initially investigated to determine the optimal measurementconditions, prior to equivalent dose determinations, which were per-formed using small aliquots and hand-picked individual grains. Small-aliquot and single-grain datasets yield comparable results, indicating thatthe former approach may be suitable for application to the majority ofsamples in this study. However, some discrepancies between the twotechniques do exist. We discuss the implications of these results, withspecific focus on the potential for using fine-sands in future dating work inCyrenaica.
OPTICALLY STIMULATED LUMINESCENCE (OSL) DATING OF ADRIATICMARINE SEDIMENTS: A TEST OF THE METHOD USING THENEAPOLITAN YELLOW TUFF TEPHRA HORIZON AS AN INDEPENDENTAGE CONTROL
Natalie Russell. Royal Holloway, University of London, United KingdomE-mail address: [email protected]
Optically Stimulated Luminescence (OSL) dating currently remains rela-tively untested in the marine realm, despite offering a potential datingrange of c. 175ka, at a precision of c. 5-10%. The Adriatic Sea represents anideal region for testing the potential of new chronological techniques,since it experiences high sedimentation rates, strong regional seasonality,and a large suite of published palaeoenvironmental proxy records, which