Reconstruction of Little Ice Age Events in the Canadian Rocky Mountains

The well-developed moraines of the Little Ice Age represent the most significant regional Holocene glacial event in the Canadian Rocky Mountains. The application of dating techniques (documentary sources, dendrochronology, lichenometry and radiocarbon dating) appropriate to this timeframe are briefly reviewed and summary data from 33 glaciers are presented. Three main periods of moraine development are recognised (i) 1500-1700 A.D., represented by small fragments of poorly dated moraines, (ii) early 1700's when about one-third of the glaciers show a maximum advance, (iii) mid-to-late-nineteenth century when major readvances built moraines close to or beyond (i) and (ii). In addition to these periods, 14C dates from overridden trees indicate a 12th/13th century glacial advance to within 400 and 1400 m of the Little Ice Age Maximum positions at Robson and Kiwa (Premier Range) Glaciers respectively. Prior to this advance a period of warmer conditions is inferred between ca. 700-1100 A.D. from the presence of large, 14C-dated snags at tree-line near the Athabasca Glacier, including a 1000 14C yr-old larch (probably Larix lyallii) about 90 km northwest of its present limit. Tree-line may have readvanced at the Athabasca site between ca. 1300-1700 A.D. but receded again during the eighteenth and nineteenth centuries. Future research should be directed towards using the relatively long tree-ring records (500-1000 yrs, with cross-dating) of this area for climatic reconstructions.Les moraines bien développées mises en place au cours du Petit Âge glaciaire sont les témoins les plus importants des glaciations holocènes dans les Rocheuses. On passe ici en revue les principales techniques de datation (sources de documentation, dendrochronologie, lichénométrie et datations au radiocarbone) appropriées à cette période et on présente les données résumées sur 33 glaciers. On a reconnu trois principales phases de développement des moraines caractérisées par: i) quelques tronçons de moraines imparfaitement datées entre 1500 et 1700 ap. J.-C. ; ii) une avancée maximale au début du XVIIIe s. pour environ le tiers des glaciers; iii) des récurrences majeures survenues de la deuxième moitié à la fin du XIXe s. qui ont rejoint sinon dépassé les positions atteintes en i) et ii). Certaines datations au radiocarbone à partir d'arbres ravagés démontrent qu'une avancée glaciaire aux XIIe et XIIIe s. s'est approchée, jusqu'à 400 et 1400 m respectivement, des positions atteintes à l'apogée du Petit Age glaciaire aux glaciers Robson et Kiwa. De grosses souches datées au 14C, situées à la limite des arbres près du glacier d'Athabaska, et notamment un mélèze vieux de 1000 ans (probablement Larix lyallii) trouvé à 90 km au nord-ouest de la limite actuelle des arbres, démontrent qu'un épisode plus chaud a prévalu entre 700 et 1100 ap. J.-C. La limite des arbres était probablement non loin de ce site vers 1300-1700 ap. J.-C, mais elle a de nouveau reculé au cours des XVIIIe et XIXe s. Les recherches sur les reconstitutions climatiques dans la région devront certainement tenir compte de cette longue série de données (500-1000 ans) sur les anneaux de croissance.Die gut entwickelten Morànen der "kleinen Eiszeit" sind das wichtigste régionale Eiszeit-Ereignis in den kanadischen Rocky Mountains wàhrend des Holozân. Die Anwendung von zu diesem Zeitrahmen passenden Datierungstechniken (dokumentarische Quellen, Dendrochronologie, Lichénométrie und Radiokarbondatierungen) werden kurz besprochen und zusammengefaBte Daten von 33 Gletschern werden vorgestellt. Drei Hauptperioden der Morànen-Entwicklung werden festgestellt : (i) 1500-1700 v.u.Z., charakterisiert durch kleine Fragmente ungenùgend datierter Morànen; (ii) eine Période des frùhen 17. Jahrhunderts, als etwa ein Drittel der Gletscher einen maximalen VorstoB aufweisen; (iii) mittleres bis spates 19. Jahrhundert, als HauptrùckvorstôBe zur Bildung von Morànen fùhrten, die denjenigen von (i) und (ii) glichen oder darùber hinausgingen. Zusâtzlich zu diesen Perioden zeigen 14C Daten von zerstôrten Bâumen einen EisvorstoB im 12./13. Jahrhundert, der sich bis auf 400 bzw. 1400 m den Maximal-Positionen der kleinen Eiszeit am Robson und Kiwagletscher nâherte. Vor diesem VorstoB wird auf eine Période wàrmerer Bedingungen geschlossen zwischen etwa 700-1100 v.u.Z., auf Grund des Vorkommens von auf 14C datierten groBen Baumstùmpfen an der Baumgrenze in der Nahe des Athabasca-Gletschers, einschlieBlich einer 1000 Jahre alten 14C Lârche (wahrscheinlich Larix lyallii), die etwa 90 km nordwestlich ihrer gegenwârtigen Grenze gefungen wurde. Die Baumgrenze ist môglicherweise zwischen 1300-1700 v.u.Z. bis zum Athabasca-Gebiet rùckvorgestoBen, dann aber wieder wàhrend des 18. und 19. Jahrhunderts zurùckgewichen. Zukùnftige Forschung ùber die klimatische Rekonstruktion sollte in diesem Gebiet auf die Nutzung der relativ langen Baumring-Belege gerichtet werden (500-1000 Jahre, mit Quer-Datierung)

The Paleoecological Record of 6 ka BP Climate in the Canadian Prairie Provinces

Synthesis of available paleoecological studies in the Prairie provinces of Canada indicates that although the peak in postglacial aridity that characterized early Holocene climate of the western foothills and plains had passed, conditions remained warmer and drier than present throughout the region ca. 6000 yr BP Compared to today, treeline elevations were higher and alpine glaciers were reduced in size in the Rocky Mountains, lake levels were lower over much of the Interior Plains, and the grassland and boreal forest ecozones extended north of their present positions. Forest fires were more prevalent ca. 6000 yr BP than they are today, aiding westward migration of jack pine (Pinus banksiana) through the boreal forest and increasing the area occupied by grassland in boreal and montane forest regions. Attempts to quantify the magnitude of 6 ka temperature and precipitation differences have produced variable results, but suggest that mean annual temperature was 0.50°C to 1.50°C higher than today (summer temperature may have been up to 3°C higher) and mean annual precipitation was reduced by 65 mm (or summer precipitation was reduced by 50 mm), compared to present. The nature and scale of these changes suggests that a vigorous zonal atmospheric circulation pattern, similar to that of the 1930s but shifted northward, prevailed at 6 ka.La synthèse des études paléoécologiques montrent qu'à 6 ka le maximum d'aridité, qui caractérisait l'Holocène inférieur, avait été atteint, mais le climat demeurait plus chaud et plus sec que maintenant dans toute la région. Les différentes limites des arbres étaient plus élevées qu'aujourd'hui et la superficie des glaciers alpins étaient plus petite, les niveaux lacustres étaient moins élevés dans la plus grande partie des plaines intérieures et les écozones des Prairies et de la forêt boréale s'étendaient plus au nord qu'aujourd'hui. Les feux de forêt étaient plus fréquents à 6 ka qu'actuellement, ce qui a favorisé la migration du pin gris (Pinus banksiana) vers l'ouest à travers la forêt boréale et accru la superficie de la prairie dans les zones de forêts boréale et alpine. Les essais faits dans le but de mesurer l'ampleur des différences de températures et de précipitations à 6 ka ont donné des résultats variables, mais montrent que la température était de 0,5 à 1,5°C plus élevé que maintenant (avec une température estivale jusqu'à 3°C plus élevée) et les précipitations annuelles moyennes étaient de 65 mm inférieures (avec des précipitations estivales de 50 mm inférieures) à maintenant. La nature et le degré des changements laissent croire qu'une forte circulation atmosphérique zonale, semblable à celle des années 1930, mais plus nordique, existait à 6 ka.Die Synthèse der verfùgbaren palâoôkologischen Studien in den Prârie-Provinzen Kanadas zeigt, daf3 das Klima in der ganzen Region um etwa 6000 Jahre v.u.Z. warmer und trockener als gegenwârtig blieb, wenn auch das Maximum an postglazialer Trockenheit, welches im frùhen Holozàn das Klima der westlichen Gebirgsauslâufer und Ebenen charakterisierte, vorùber war. Verglichen mit heute waren die Baumgrenzen hôher und die alpinen Gletscher in den Rocky Mountains kleiner, die Seehôhen waren niedriger im grôBten Teil der inneren Ebenen, und die Ôkozonen von Grasland und nôrdlichem WaId erstreckten sich weiter nôrdlich als heute. Waldbrânde traten um etwa 6000 v.u.Z. hâufiger als gegenwârtig auf und haben so die Westwàrtswanderung von Graukiefer (Pinus banksiana) durch den nôrdlichen WaId begùnstigt und die Graslandflàchen in den Gebieten des nôrdlichen und alpinen Waldes vergrôBert. Versuche, den Umfang der Unterschiede in Temperatur und Niederschlàgen um 6 ka zu bestimmen, ergaben wechselnde Ergebnissse, doch zeigen sie, daB die durchschnittliche jâhrliche Temperatur 0.5° C bis 1.50C hôher als gegenwârtig war (die Sommertemperatur dûrfte bis zu 3°C hôher gewesen sein) und die durchschnittlichen jâhrlichen Niederschlâge waren um 65 mm geringer (oder die Sommer-Niederschlàge waren um 50 mm geringer) verglichen mit heute. Die Natur und der Grad dieser Wechsel lassen vermuten, daB eine krâftige zonale atmosphàrische Strômung, àhnlich der von den 1930 iger Jahren aber nôrdlicher gelagert, um 6 ka vorherrschte

Proxy Climatic Data from Tree Rings at Lake Louise, Alberta : A Preliminary Report

Preliminary results are presented of studies using oxygen isotopes and tree-ring densitometry to derive proxy climatic data from Picea engelmannii and Abies Iasiocarpa in the Canadian Rockies. Significant correlations occur between mean annual temperatures and δ18O determinations from five year groups of tree rings from three trees. However, unexplained anomalies in these relationships indicate that ring-width effects may reduce this correlation in some cases and that further exploratory work is necessary. Indexed chronologies for the period 1705-1980 were developed for 15 tree-ring variables derived by X-ray densitometry from 16 Picea cores. Principal components analysis was used to identify three groups of highly inter-correlated variables related to ring width, earlywood density and latewood characteristics. Each group responds differently to climatic controls increasing the potential for development of proxy climatic data over ring-width measures alone. Transfer function development is incomplete but preliminary results for summer temperature (June and July, R2 = 0,46) and December-March precipitation (R2 = 0,40) are presented as examples. Using these equations preliminary reconstructions for the period 1710-1980 are presented.On présente ici les résultats préliminaires d'études dont le but est d'obtenir des données climatiques par l'intermédiaire, chez Picea engelmannii et Abies lasiocarpa, dans les Rocheuses du Canada, des isotopes d'oxygène et de la densité des anneaux de croissance. On obtient des corrélations significatives entre les températures moyennes annuelles et les déterminations au δ18O sur les anneaux de croissance de trois arbres, par périodes de 5 ans. Toutefois, des anomalies encore inexpliquées révèlent que certaines caractéristiques de la largeur des anneaux pourraient, dans certains cas, réduire la corrélation. Il est donc nécessaire de poursuivre les recherches dans ce domaine. On a dressé des répertoires chronologiques, allant de 1705 à 1980. Ils tiennent compte de 15 variables provenant des anneaux de croissance et obtenues par densitométrie ra-diologique sur 16 noyaux de Picea. On a ensuite réparti les variables en trois groupes principaux en se fondant sur la largeur des anneaux, la densité du bois de printemps et les particularités du bois d'automne. Chaque groupe réagit différemment au climat, si bien que les données climatiques indirectes risquent d'être plus importantes que celles que fournissent les seules mesures de largeur des anneaux de croissance. L'élaboration de la fonction de transfert est incomplète, mais on donne, à titre d'exemple, les résultats préliminaires touchant les températures d'été de juin à juillet (R2 = 0,46) et les précipitations de décembre à mars (R2 = 0,40). À l'aide de ces équations on a pu effectuer des reconstitutions climatiques préliminaires pour la période allant de 1710 à 1980.Es werden vorlâufige Ergebnisse vorgestellt von Studien. die mittels Sauerstoff-lsotopen und der Dichte der Baumjahresringe indirekte klimatische Daten von Picea engelmannii und Abies Iasiocarpa in den kanadischen Rockies gewinnen. Es erscheinen signifikante Korrelationen zwischen durchschnittlichen Jahrestemperaturen und den δ18O Bestimmungen auf den Jahresringen von drei Bâu-men in fùnf Jahresgruppen. Jedoch weisen unerklàrte Anomalien in diesen Beziehungen darauf hin, daB Wirkungen der Ring-Breite dièse Korrelation in manchen Fallen reduzieren kann, und dafî weitere Forschungsarbeit notwendig ist. Fur die Zeit von 1705-1980 wurden chronologische Register entwickelt fur 15 Baum-Ring-Variablen. Dièse wurden durch Messung der Dichte von 16 Picea Kernen mittels Rôntgenaufnahmen gewonnen. Die Analyse der hauptsàchlichen Komponenten diente der Identifizierung von drei Gruppen von Variablen, die in intensiver Wechselbeziehung stehen, wobei man sich auf die Breite der Ringe, die Dichte des Frùhjahrsbaumwuchses und die Charakteristika des Herbstbaumwuchses bezog. Jede Gruppe reagiert anders auf klimatische Einflùsse, so daB die indirekt gewonnenen klimatischen Daten wichtiger sind, als die allein durch Messung der Ring-Weite gewonnenen. Die Ausarbeitung der Transferfunktion ist unvollstândig, aber vorlâufige Ergebnisse fur Sommertemperatur (Juni und JuIi, R2 = 0.46) und Dezember bis Màrz Niederschlag (R2 = 0.40) werden als Beispiel dargestellt. Mittels dieser Gleichungen werden vorlâufige Rekonstruktionen fur die Période von 1710 bis 1980 vorgestellt

Rapidly changing subglacial hydrological pathways at a tidewater glacier revealed through simultaneous observations of water pressure, supraglacial lakes, meltwater plumes and surface velocities

This work was funded by the Conoco Phillips-Lundin Northern Area Program through the CRIOS project (Calving Rates and Impact On Sea level, http://www.researchinsvalbard.no/project/7037). Penelope How is supported by a NERC PhD studentship.Subglacial hydrological processes at tidewater glaciers remain poorly understood due to the difficulty in obtaining direct measurements and lack of empirical verification for modelling approaches. Here, we investigate the subglacial hydrology of Kronebreen, a fast-flowing tidewater glacier in Svalbard during the 2014 melt season. We combine observations of borehole water pressure, supraglacial lake drainage, surface velocities and plume activity with modelled run-off and water routing to develop a conceptual model that thoroughly encapsulates subglacial drainage at a tidewater glacier. Simultaneous measurements suggest that an early-season episode of subglacial flushing took place during our observation period, and a stable efficient drainage system effectively transported subglacial water through the northern region of the glacier tongue. Drainage pathways through the central and southern regions of the glacier tongue were disrupted throughout the following melt season. Periodic plume activity at the terminus appears to be a signal for modulated subglacial pulsing, i.e. an internally driven storage and release of subglacial meltwater that operates independently of marine influences. This storage is a key control on ice flow in the 2014 melt season. Evidence from this work and previous studies strongly suggests that long-term changes in ice flow at Kronebreen are controlled by the location of efficient/inefficient drainage and the position of regions where water is stored and released.Publisher PDFPeer reviewe

Streamflow variations across the Andes (18°–55°S) during the instrumental era

The rivers originating in the southern Andes (18°–55°S) support numerous ecosystems and a large number of human populations and socio-economic activities in the adjacent lowlands of Chile, Argentina and Bolivia. Here we show that ca. 75% of the total variance in the streamflow records from this extensive region can be explained by only eight spatially coherent patterns of variability. Five (three) of these Andean patterns exhibit extreme dry (wet) conditions in recent years, with strong interannual variations in northern Chile; long-term drying trends between 31° and 41°S; a transitional pattern in the central Patagonian Andes; and increasing trends in northwestern Argentina and southern Bolivia, the Fueguian Andes, and the eastern portion of the South Patagonian Icefield. Multivariate regression analyses show that large-scale indices of ENSO variability can predict 20% to 45% of annual runoff variability between 28° and 46°S. The influence of Antarctic and North Pacific indices becomes more relevant south of 43°S and in northwestern Argentina and southern Bolivia, respectively, but their overall skill as predictors of Andean streamflows is weak. The analyses provide relevant new information to improve understanding of the spatial coherence, the main temporal features, and the ocean-atmospheric forcings of surface runoff across the southern Andes.Fil: Masiokas, Mariano Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Cara Ramirez, Leandro Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Pitte, Pedro Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Luckman, B. H.. University of Western Ontario; CanadáFil: Toum, Jorge Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Christie, D. A.. Universidad Austral de Chile; Chile. Center For Climate And Resilience Research; ChileFil: Le Quesne, C.. Universidad Austral de Chile; ChileFil: Mauget, S.. United States Department of Agriculture. Agriculture Research Service; Estados Unido

Physical conditions of fast glacier flow:3. Seasonally-evolving ice deformation on Store Glacier, West Greenland

Temporal variations in ice sheet flow directly impact the internal structure within ice sheets through englacial deformation. Large‐scale changes in the vertical stratigraphy within ice sheets have been previously conducted on centennial to millennial timescales; however, intra‐annual changes in the morphology of internal layers have yet to be explored. Over a period of 2 years, we use autonomous phase‐sensitive radio‐echo sounding to track the daily displacement of internal layers on Store Glacier, West Greenland, to millimeter accuracy. At a site located ∼30 km from the calving terminus, where the ice is ∼600 m thick and flows at ∼700 m/a, we measure distinct seasonal variations in vertical velocities and vertical strain rates over a 2‐year period. Prior to the melt season (March–June), we observe increasingly nonlinear englacial deformation with negative vertical strain rates (i.e., strain thinning) in the upper half of the ice column of approximately −0.03 a⁻¹, whereas the ice below thickens under vertical strain reaching up to +0.16 a⁻¹. Early in the melt season (June–July), vertical thinning gradually ceases as the glacier increasingly thickens. During late summer to midwinter (August–February), vertical thickening occurs linearly throughout the entire ice column, with strain rates averaging 0.016 a⁻¹. We show that these complex variations are unrelated to topographic setting and localized basal slip and hypothesize that this seasonality is driven by far‐field perturbations in the glacier's force balance, in this case generated by variations in basal hydrology near the glacier's terminus and propagated tens of kilometers upstream through transient basal lubrication longitudinal coupling

Creative aspiration and the betrayal of promise? The experience of new creative workers

The promise of ‘doing what you love’ continues to attract new aspirants to creative work, yet most creative industries are so characterised by low investment, shifting foci and ongoing technological innovation that all promises must be unreliable. Some would-be creative workers negotiate their own pathways from the outset, ‘following their dream’ as they attempt to convert personal enthusiasms and amateur activities into income-earning careers. Others look to the proliferation of available training and education options, including higher education courses, as possible pathways into creative work. This chapter reviews recent research from the USA, Australia and the UK on the effectiveness – or otherwise – of higher education as preparation for a creative career. The chapter discusses the obstacles that many creative workers, including graduates, encounter on their creative pathways, for instance, as a result of informal work practices and self-employment. The chapter also looks at sources of advantage and disadvantage, such as those associated with particular geographic locations or personal identities. The chapter concludes by introducing the subsequent chapters in the collection. These critically explore the experience of new creative workers in a wide range of national contexts including Australia, Belgium, China, Ireland, Italy, Finland, the Netherlands, Russia and the United Kingdom

Spatiotemporal interpolation of elevation changes derived from satellite altimetry for Jakobshavn Isbræ, Greenland

Estimation of ice sheet mass balance from satellite altimetry requires interpolation of point-scale elevation change (dHdt) data over the area of interest. The largest dHdt values occur over narrow, fast-flowing outlet glaciers, where data coverage of current satellite altimetry is poorest. In those areas, straightforward interpolation of data is unlikely to reflect the true patterns of dHdt. Here, four interpolation methods are compared and evaluated over Jakobshavn Isbr, an outlet glacier for which widespread airborne validation data are available from NASAs Airborne Topographic Mapper (ATM). The four methods are ordinary kriging (OK), kriging with external drift (KED), where the spatial pattern of surface velocity is used as a proxy for that of dHdt, and their spatiotemporal equivalents (ST-OK and ST-KED)

Extensive retreat of Greenland tidewater glaciers 2000-2010

Overall mass loss from the Greenland ice sheet nearly doubled during the early 2000s resulting in an increased contribution to sea-level rise, with this step-change being mainly attributed to the widespread frontal retreat and accompanying dynamic thinning of tidewater glaciers. Changes in glacier calving-front positions are easily derived from remotely sensed imagery and provide a record of dynamic change. However, ice-sheet-wide studies of calving fronts have been either spatially or temporally limited. In this study multiple calving-front positions were derived for 199 Greenland marine-terminating outlet glaciers with width greater than 1 km using Landsat imagery for the 11-year period 2000–2010 in order to identify regional seasonal and inter-annual variations. During this period, outlet glaciers were characterized by sustained and substantial retreat summing to more than 267 km, with only 11 glaciers showing overall advance. In general, the pattern of mass loss detected by GRACE (Gravity Recovery and Climate Experiment) and other measurements is reflected in the calving record of Greenland glaciers. Our results suggest several regions in the south and east of the ice sheet likely share controls on their dynamic changes, but no simple single control is apparent

A Reconciled Estimate of Ice-Sheet Mass Balance

We combined an ensemble of satellite altimetry, interferometry, and gravimetry data sets using common geographical regions, time intervals, and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of Earth's polar ice sheets. We find that there is good agreement between different satellite methods-especially in Greenland and West Antarctica-and that combining satellite data sets leads to greater certainty. Between 1992 and 2011, the ice sheets of Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula changed in mass by -142 plus or minus 49, +14 plus or minus 43, -65 plus or minus 26, and -20 plus or minus 14 gigatonnes year(sup 1), respectively. Since 1992, the polar ice sheets have contributed, on average, 0.59 plus or minus 0.20 millimeter year(sup 1) to the rate of global sea-level rise