Warming of the Antarctic ice-sheet surface since the 1957 International Geophysical Year

Assessments of Antarctic temperature change have emphasized the contrast between strong warming of the Antarctic Peninsula and slight cooling of the Antarctic continental interior in recent decades. This pattern of temperature change has been attributed to the increased strength of the circumpolar westerlies, largely in response to changes in stratospheric ozone. This picture, however, is substantially incomplete owing to the sparseness and short duration of the observations. Here we show that significant warming extends well beyond the Antarctic Peninsula to cover most of West Antarctica, an area of warming much larger than previously reported. West Antarctic warming exceeds 0.1 °C per decade over the past 50 years, and is strongest in winter and spring. Although this is partly offset by autumn cooling in East Antarctica, the continent-wide average near-surface temperature trend is positive. Simulations using a general circulation model reproduce the essential features of the spatial pattern and the long-term trend, and we suggest that neither can be attributed directly to increases in the strength of the westerlies. Instead, regional changes in atmospheric circulation and associated changes in sea surface temperature and sea ice are required to explain the enhanced warming in West Antarctica

Particulate and water-soluble carbon measured in recent snow at Summit, Greenland

Water-soluble organic carbon (WSOC), waterinsoluble particulate organic carbon (WIOC), and particulate elemental carbon (EC) were measured simultaneously for the first time on the Greenland Ice Sheet in surface snow and in a 3-meter snow pit. Snow pit concentrations reveal that, on average, WSOC makes up the majority (89%) of carbonaceous species, followed by WIOC (10%) and EC (1%). The enhancement of OC relative to EC (ratio 99:1) in Greenland snow suggests that, along with atmospheric particulate matter, gaseous organics contribute to snow-phase OC. Comparison of summer surface snow concentrations in 2006 with past summer snow pit layers (2002 – 2005) found a significant depletion in WSOC (20 – 82%) and WIOC (46 – 65%) relative to EC for 3 of the 4 years. The apparent substantial loss of WSOC and WIOC in aged snow suggests that post-depositional processes, such as photochemical reactions, need to be considered in linking ice core records of organics to atmospheric concentrations. Citation: Hagler, G. S. W., M. H. Bergin, E. A. Smith, J. E. Dibb, C. Anderson, and E. J. Steig (2007), Particulate and water-soluble carbon measured in recent snow at Summit, Greenland, Geophys. Res. Lett., 34, L16505, doi:10.1029/2007GL030110

An automated approach for annual layer counting in ice cores

A novel method for automated annual layer counting in seasonally-resolved paleoclimate records has been developed. It relies on algorithms from the statistical framework of hidden Markov models (HMMs), which originally was developed for use in machine speech recognition. The strength of the layer detection algorithm lies in the way it is able to imitate the manual procedures for annual layer counting, while being based on statistical criteria for annual layer identification. The most likely positions of multiple layer boundaries in a section of ice core data are determined simultaneously, and a probabilistic uncertainty estimate of the resulting layer count is provided, ensuring an objective treatment of ambiguous layers in the data. Furthermore, multiple data series can be incorporated and used simultaneously. In this study, the automated layer counting algorithm has been applied to two ice core records from Greenland: one displaying a distinct annual signal and one which is more challenging. The algorithm shows high skill in reproducing the results from manual layer counts, and the resulting timescale compares well to absolute-dated volcanic marker horizons where these exist

Antarctic Ice Sheet Elevation Impacts on Water Isotope Records During the Last Interglacial

Changes of the topography of the Antarctic ice sheet (AIS) can complicate the interpretation of ice core water stable isotope measurements in terms of temperature. Here, we use a set of idealised AIS elevation change scenarios to investigate this for the warm Last Interglacial (LIG). We show that LIG δ 18 O against elevation relationships are not uniform across Antarctica, and that the LIG response to elevation is lower than the preindustrial response. The effect of LIG elevation‐induced sea ice changes on δ 18 O is small, allowing us to isolate the effect of elevation change alone. Our results help to define the effect of AIS changes on the LIG δ 18 O signals, and should be invaluable to those seeking to use AIS ice core measurements for these purposes. Especially, our simulations strengthen the conclusion that ice core measurements from the Talos Dome core exclude the loss of the Wilkes Basin at around 128 ky

A 700 year record of Southern Hemisphere extratropical climate variability

Annually dated ice cores from West and East Antarctica provide proxies for past changes in atmospheric circulation over Antarctica and portions of the Southern Ocean, temperature in coastal West and East Antarctica, and the frequency of South Polar penetration of El Niño events. During the period AD 1700–1850, atmospheric circulation over the Antarctic and at least portions of the Southern Hemisphere underwent a mode switch departing from the out-of-phase alternation of multi-decadal long phases of EOF1 and EOF2 modes of the 850 hPa field over the Southern Hemisphere (as defined in the recent record by Thompson and Wallace, 2000; Thompson and Solomon, 2002) that characterizes the remainder of the 700 year long record. From AD 1700 to 1850, lower-tropospheric circulation was replaced by in-phase behavior of the Amundsen Sea Low component of EOF2 and the East Antarctic High component of EOF1. During the first phase of the mode switch, both West and East Antarctic temperatures declined, potentially in response to the increased extent of sea ice surrounding both regions. At the end of the mode switch, West Antarctic coastal temperatures rose and East Antarctic coastal temperatures fell, respectively, to their second highest and lowest of the record. Polar penetration of El Niño events increased during the mode switch. The onset of the AD 1700–1850 mode switch coincides with the extreme state of the Maunder Minimum in solar variability. Late 20th-century West Antarctic coastal temperatures are the highest in the record period, and East Antarctic coastal temperatures close to the lowest. Since AD 1700, extratropical regions of the Southern Hemisphere have experienced significant climate variability coincident with changes in both solar variability and greenhouse gase

The use of natural resources to improve household income, health, and nutrition within the forests of Kianjavato, Madagascar

Understanding natural resource extraction in Madagascar is key to developing wider conservation and management strategies that ensure the continued delivery of essential ecosystem services, and the development of health and economic strategies to meet the demands of a growing human population. In the Kianjavato lowland rainforest of southeastern Madagascar, 78% of lemur species, 83% of native carnivoran species, and 67% of frugivorous bat species are threatened with extinction. All three of these groups of mammals are commonly hunted for food in other regions of Madagascar, yet we know little about current levels of hunting or whether the use of forest resources significantly affects human welfare in this region. We used health assessments of 1267 Kianjavato residents and semi-structured interviews of members of 336 households in 17 communities in Kianjavato to investigate human-environmental interactions. We found high prevalence of child and teenage malnutrition. More than half of the population under 20 years old was stunted, more than half was underweight, and more than one fifth was wasted. Further, one in six residents were anemic. We found that Kianjavato’s forests provided essential ecosystem services for its rural communities. As Kianjavato’s forests are altered to meet the needs of a growing human population, these direct-use ecosystem services (such as the use of wild animals for food or plants for medicine) are unable to similarly expand to meet the basic needs of the families living in these forests. A worrying proportion of the Kianjavato population depends on forests to meet their healthcare, nutritional, and economic needs, yet they may be failing to do so. All surveyed households (100%) depended on forests to meet their healthcare needs and 40% of the regional economy involved the extraction of finite forest resources (i.e., precious stones). Most households consumed very little wildlife (two animals per household per year) and the great majority (83%) of the forest animals they ate were not threatened with extinction. Forty percent of wildlife were caught illegally. Although hunting is likely not imperiling local wildlife at present, 16% of the Kianjavato population hunts wildlife and 20% are malnourished. The ecosystem services of Kianjavato’s forests may currently be insufficient to meet the needs of residents. Therefore, targeted efforts to increase local access to the healthcare system and to improve household nutrition and economy by improving the production and stability of local agricultural products may increase the long-term sustainability of both wildlife hunting, household incomes, and regional food security. Efforts such as these that can expand with the growing population to meet future needs may help secure the sustainable use of essential ecosystem services for the long term, improving the health of local people and maintaining the integrity of the forests in which they live. RésuméComprendre l'utilisation des ressources naturelles à Madagascar est essentiel pour développer des stratégies de conservation et de gestion plus larges qui permettent à la fois de fournir des services écosystémiques et de développer des stratégies sanitaires et économiques afin de répondre aux besoins d'une population humaine toujours croissante. Dans la forêt tropicale humide de basse altitude de Kianjavato dans le sud-est de Madagascar, 78% des espèces de lémuriens, 83% des espèces de carnivores indigènes et 67% des espèces de chauves-souris frugivores sont menacés d'extinction. Ces trois groupes de mammifères sont généralement chassés dans d'autres régions de Madagascar, mais nous en savons peu sur les niveaux actuels de chasse ou si l'utilisation des ressources forestières affecte significativement le bien-être humain dans cette région. Nous avons conduit une évaluation sanitaire sur 1267 habitants de Kianjavato, ainsi que des entretiens semi-structurés avec des membres de 336 ménages dans 17 communautés de Kianjavato afin d’étudier les interactions entre l’Homme et l’environnement. Nous avons constaté une forte prévalence de la malnutrition chez les enfants et les adolescents. Plus de la moitié de la population âgée de moins de 20 ans souffre d'un retard de croissance, plus de la moitié d’une insuffisance pondérale et plus d'un cinquième d’émaciation. En outre, un résident sur six est anémique. Nous avons constaté que les forêts de Kianjavato fournissent des services écosystémiques essentiels à ces communautés rurales. Comme les forêts de Kianjavato sont altérées pour répondre aux besoins d'une population croissante, ces services écosystémiques à usage direct (tels que la consommation d'animaux sauvages ou des plantes médicinales) ne peuvent plus couvrir les besoins fondamentaux des familles qui y vivent. Une proportion inquiétante de la population de Kianjavato dépend des forêts quant à ses besoins sanitaires, nutritionnels et économiques, cependant ces dernières ne peuvent plus y pourvoir entièrement. Tous les ménages enquêtés (100%) comptent sur la forêt pour la satisfaction de leurs besoins sanitaires. Par ailleurs, l’exploitation de ressources forestières finies (extraction de pierres précieuses) représente 40% de l’économie régionale. La plupart des ménages consommaient très peu d'animaux sauvages (deux animaux par ménage par an) et la grande majorité (83%) des animaux forestiers qu'ils mangeaient n'étaient pas menacés d'extinction. Cependant, 40% de ces animaux forestiers ont été capturés de manière illicite. Certes la chasse ne menace pas actuellement la faune locale mais 16% de la population de Kianjavato reconnaît s’y adonner et 20% souffrent de malnutrition. Les services écosystémiques s’avèrent actuellement insuffisants pour répondre aux besoins des résidents. Il est par conséquent nécessaire de cibler les efforts pour accroître l’accès local au système de santé, ensuite pour améliorer la nutrition et l’économie des ménages (améliorer la production et la stabilité des produits agricoles locaux), et tout ceci dans le but d’augmenter la viabilité à long terme de la chasse, des revenus et de la sécurité alimentaire dans cette région. De tels efforts lorsqu’ils prennent en compte la croissance de la population - et donc ses besoins futurs accrus —peuvent aider à assurer l’utilisation durable des services écosystémiques, à améliorer la santé des populations locales, et en fin de compte, à maintenir l’intégrité des forêts dans lesquelles elles vivent

The use of natural resources to improve household income, health, and nutrition within the forests of Kianjavato, Madagascar

Understanding natural resource extraction in Madagascar is key to developing wider conservation and management strategies that ensure the continued delivery of essential ecosystem services, and the development of health and economic strategies to meet the demands of a growing human population. In the Kianjavato lowland rainforest of southeastern Madagascar, 78% of lemur species, 83% of native carnivoran species, and 67% of frugivorous bat species are threatened with extinction. All three of these groups of mammals are commonly hunted for food in other regions of Madagascar, yet we knew little about current levels of hunting or whether the use of forest resources significantly affects human welfare in this region. We used health assessments of 1 267 Kianjavato residents and semi-structured interviews of members of 336 households in 1 7 communities in Kianjavato to investigate human-environmental interactions. We found high prevalence of child and teenage malnutrition. More than half of the population under 20 years old was stunted, more than half was underweight, and more than one fifth was wasted. Further, one in six residents were anemic. We found that Kianjavato’s forests provided essential ecosystem services for its rural communities. As Kianjavato’s forests are altered to meet the needs of a growing human population, these direct-use ecosystem services (such as the use of wild animals for food or plants for medicine) are unable to similarly expand to meet the basic needs of the families living in these forests. A worrying proportion of the Kianjavato population depends on forests to meet their healthcare, nutritional, and economic needs, yet they may be failing to do so. All surveyed households (1 00%) depended on forests to meet their healthcare needs and 40% of the regional economy involved the extraction of finite forest resources (i.e., precious stones). Most  households consumed very little wildlife (two animals per household per year) and the great majority (83%) of the forest animals they ate were not threatened with extinction. Forty percent of wildlife were caught illegally. Although hunting is likely not imperiling local wildlife at present, 1 6% of the Kianjavato population hunts wildlife and 20% are malnourished. The ecosystem services of Kianjavato’s forests may currently be insufficient to meet the needs of residents. Therefore, targeted efforts to increase local access to the healthcare system and to improve household nutrition and economy by improving the production and stability of local agricultural products may increase the long-term sustainability of wildlife hunting, household incomes, and regional food security. Efforts such as these that can expand with the growing population to meet future needs may help secure the sustainable use of essential ecosystem services for the long term, improving the health of local people and maintaining the integrity of the forests in which they live

Ice sheet record of recent sea-ice behavior and polynya variability in the Amundsen Sea, West Antarctica

Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 118 (2013): 118–130, doi:10.1029/2012JC008077.Our understanding of past sea-ice variability is limited by the short length of satellite and instrumental records. Proxy records can extend these observations but require further development and validation. We compare methanesulfonic acid (MSA) and chloride (Cl–) concentrations from a new firn core from coastal West Antarctica with satellite-derived observations of regional sea-ice concentration (SIC) in the Amundsen Sea (AS) to evaluate spatial and temporal correlations from 2002–2010. The high accumulation rate (~39 g∙cm–2∙yr–1) provides monthly resolved records of MSA and Cl–, allowing detailed investigation of how regional SIC is recorded in the ice-sheet stratigraphy. Over the period 2002–2010 we find that the ice-sheet chemistry is significantly correlated with SIC variability within the AS and Pine Island Bay polynyas. Based on this result, we evaluate the use of ice-core chemistry as a proxy for interannual polynya variability in this region, one of the largest and most persistent polynya areas in Antarctica. MSA concentrations correlate strongly with summer SIC within the polynya regions, consistent with MSA at this site being derived from marine biological productivity during the spring and summer. Cl– concentrations correlate strongly with winter SIC within the polynyas as well as some regions outside the polynyas, consistent with Cl– at this site originating primarily from winter sea-ice formation. Spatial correlations were generally insignificant outside of the polynya areas, with some notable exceptions. Ice-core glaciochemical records from this dynamic region thus may provide a proxy for reconstructing AS and Pine Island Bay polynya variability prior to the satellite era.This research was supported by an award from the Department of Energy Office of Science Graduate Fellowship Program (DOE SCGF) to ASC, a James E. and Barbara V. Moltz Research Fellowship to SBD, and by grants from NSF-OPP (#ANT-0632031 & #ANT-0631973); NSF-MRI (#EAR-1126217); NASA Cryosphere Program (#NNX10AP09G); and a WHOI Andrew W. Mellon Foundation Award for Innovative Research.2013-07-2

Dust Transport to the Taylor Glacier, Antarctica, During the Last Interglacial

Changes in the composition of dust trapped in ice provide evidence of past atmospheric circulation and earth surface conditions. Investigations of dust provenance in Antarctic ice during glacial and interglacial periods indicate that South America is the primary dust source during both climate regimes. Here, we present results from a new ice core dust archive extracted from the Taylor Glacier in coastal East Antarctica during the deglacial transition from Marine Isotope Stage 6 to 5e. Radiogenic strontium and neodymium isotopes indicate that last interglacial dust is young and volcanic, in contrast to the observed preindustrial and Holocene (Marine Isotope Stage 1) dust composition. The dust composition differences from the last interglacial and current interglacial period at the site require a profound difference in atmospheric transport and environmental conditions. We consider several potential causes for enhanced transport of volcanic material to the site, including increased availability of volcanic material and large‐scale atmospheric circulation changes.Plain Language SummaryFluctuations in the isotopic composition of dust particles transported atmospherically and trapped in East Antarctic ice during glacial and interglacial periods provide glimpses into past earth surface conditions and atmospheric dynamics through time. Here we present new ice core records of dust from the Taylor Glacier (Antarctica), extending back to the transition into the last interglacial period (~130,000 years ago). Dust deposited at this site during the last interglacial period has a significantly more volcanic dust composition compared to the current interglacial dust, caused by a pronounced wind direction change and/or increased subaerial exposure of volcanic material. The distinct dust compositions during two separate interglacial periods suggest significant differences in conditions at the dust source areas and atmospheric dynamics to this peripheral Antarctic site.Key PointsLast interglacial dust composition in Taylor Glacier ice is distinct from MIS 1 recordSr and Nd isotope signatures indicate a young volcanic sourceGeochemical data suggest a change in provenance and atmospheric circulation between MIS 5e and MIS 1Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/148354/1/grl58638_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148354/2/grl58638.pd