@misc{KienelWulfBowenByrneetal.2009,
  author    = {Kienel, Ulrike and Wulf Bowen, Sabine and Byrne, Roger and Park, Jungjae and B{\"o}hnel, Harald and Dulski, Peter and Luhr, James F. and Siebert, Lee and Haug, Gerald H. and Negendank, J{\"o}rg F. W.},
  title     = {First lacustrine varve chronologies from Mexico},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe},
  number    = {860},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-43279},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-432794},
  pages     = {587 -- 609},
  year      = {2009},
  abstract  = {We present varve chronologies for sediments from two maar lakes in the Valle de Santiago region (Central Mexico): Hoya La Alberca (AD 1852-1973) and Hoya Rincn de Parangueo (AD 1839-1943). These are the first varve chronologies for Mexican lakes. The varved sections were anchored with tephras from Colima (1913) and Paricutin (1943/1944) and (210)Pb ages. We compare the sequences using the thickness of seasonal laminae and element counts (Al, Si, S, Cl, K, Ti, Mn, Fe, and Sr) determined by micro X-ray fluorescence spectrometry. The formation of the varve sublaminae is attributed to the strongly seasonal climate regime. Limited rainfall and high evaporation rates in winter and spring induce precipitation of carbonates (high Ca, Sr) enriched in (13)C and (18)O, whereas rainfall in summer increases organic and clastic input (plagioclase, quartz) with high counts of lithogenic elements (K, Al, Ti, and Si). Eolian input of Ti occurs also in the dry season. Moving correlations (5-yr windows) of the Ca and Ti counts show similar development in both sequences until the 1930s. Positive correlations indicate mixing of allochthonous Ti and autochthonous Ca, while negative correlations indicate their separation in sublaminae. Negative excursions in the correlations correspond with historic and reconstructed droughts, El Nio events, and positive SST anomalies. Based on our data, droughts (3-7 year duration) were severe and centred around the following years: the early 1850s, 1865, 1880, 1895, 1905, 1915 and the late 1920s with continuation into the 1930s. The latter dry period brought both lake systems into a critical state making them susceptible to further drying. Groundwater overexploitation due to the expansion of irrigation agriculture in the region after 1940 induced the transition from calcite to aragonite precipitation in Alberca and halite infiltration in Rincn. The proxy data indicate a faster response to increased evaporation for Rincn, the lake with the larger maar dimensions, solar radiation receipt and higher conductivity, whereas the smaller, steeper Alberca maar responded rapidly to increased precipitation.},
  language  = {en}
}
@article{BakkeLieHeegaardetal.2009,
  author    = {Bakke, Jostein and Lie, {\O}yvind and Heegaard, Einar and Dokken, Trond and Haug, Gerald H. and Birks, Hilary H. and Dulski, Peter and Nilsen, Trygve},
  title     = {Rapid oceanic and atmospheric changes during the Younger Dryas cold period},
  issn      = {1752-0894},
  doi       = {10.1038/ngeo439},
  year      = {2009},
  abstract  = {The Younger Dryas event, which began approximately 12,900 years ago, was a period of rapid cooling in the Northern Hemisphere, driven by large-scale reorganizations of patterns of atmospheric and oceanic circulation(1-3). Environmental changes during this period have been documented by both proxy-based reconstructions(3) and model simulations(4), but there is currently no consensus on the exact mechanisms of onset, stabilization or termination of the Younger Dryas(5-8). Here we present high-resolution records from two sediment cores obtained from Lake Krakenes in western Norway and the Nordic seas. Multiple proxies from Lake Krakenes are indicative of rapid alternations between glacial growth and melting during the later Younger Dryas. Meanwhile, reconstructed sea surface temperature and salinity from the Nordic seas show an alternation between sea-ice cover and the influx of warm, salty North Atlantic waters. We suggest that the influx of warm water enabled the westerly wind systems to drift northward, closer to their present-day positions. The winds thus brought relatively warm maritime air to Northern Europe, resulting in rising temperatures and the melting of glaciers. Subsequent input of this fresh meltwater into the ocean spurred the formation of sea ice, which forced the westerly winds back to the south, cooling Northern Europe. We conclude that rapid alternations between these two states immediately preceded the termination of the Younger Dryas and the permanent transition to an interglacial state.},
  language  = {en}
}
@article{JaccardGalbraithSigmanetal.2009,
  author    = {Jaccard, Samuel Laurent and Galbraith, Eric D. and Sigman, Daniel M. and Haug, Gerald H. and Francois, Roger and Pedersen, Thomas F. and Dulski, Peter and Thierstein, Hans R.},
  title     = {Subarctic Pacific evidence for a glacial deepening of the oceanic respired carbon pool},
  issn      = {0012-821X},
  doi       = {10.1016/j.epsl.2008.10.017},
  year      = {2009},
  abstract  = {Measurements of benthic foraminiferal cadmium:calcium (Cd/Ca) have indicated that the glacial-interglacial change in deep North Pacific phosphate (PO4) concentration was minimal which has been taken by some, workers as a sign that the biological pump did not store more carbon in the deep glacial ocean. Here we present sedimentary redox- sensitive trace metal records from Ocean Drilling Program (ODP) Site 882 (NW subarctic Pacific, water depth 3244 m) to make inferences about changes in deep North Pacific oxygenation and thus respired carbon storage - over the past 150,000 yr. These observations are complemented with biogenic barium and opal measurements as indicators for past organic carbon export to separate the influences of deep-water oxygen concentration and sedimentary organic carbon respiration on the redox state of the sediment. Our results suggest that the deep subarctic Pacific water mass was deleted in ox en during glacial maxima, though it was not anoxic. We reconcile our results with the existing benthic foraminiferal Cd/Ca by invoking a decrease in the fraction of the deep ocean nutrient inventory that was preformed, rather than remineralized. This change would have corresponded to an increase in the deep Pacific storage of respired carbon, which Would have lowered atmospheric carbon dioxide (CO2) by sequestering CO2 away from the atmosphere and by increasing ocean alkalinity through a transient dissolution event in the deep sea. The magnitude of change in preformed nutrients suggested by the North Pacific data Would have accounted for a majority of the observed decrease in glacial atmospheric PCO2.},
  language  = {en}
}
@article{KienelBowenByrneetal.2009,
  author    = {Kienel, Ulrike and Bowen, Sabine Wulf and Byrne, Roger and Park, Jungjae and Boehnel, Harald and Dulski, Peter and Luhr, James F. and Siebert, Lee and Haug, Gerald H. and Negendank, Joerg F. W.},
  title     = {First lacustrine varve chronologies from Mexico : impact of droughts, ENSO and human activity since AD 1840 as recorded in maar sediments from Valle de Santiago},
  issn      = {0921-2728},
  doi       = {10.1007/s10933-009-9307-x},
  year      = {2009},
  abstract  = {We present varve chronologies for sediments from two maar lakes in the Valle de Santiago region (Central Mexico): Hoya La Alberca (AD 1852-1973) and Hoya Rincn de Parangueo (AD 1839-1943). These are the first varve chronologies for Mexican lakes. The varved sections were anchored with tephras from Colima (1913) and Paricutin (1943/ 1944) and Pb-210 ages. We compare the sequences using the thickness of seasonal laminae and element counts (Al, Si, S, Cl, K, Ti, Mn, Fe, and Sr) determined by micro X-ray fluorescence spectrometry. The formation of the varve sublaminae is attributed to the strongly seasonal climate regime. Limited rainfall and high evaporation rates in winter and spring induce precipitation of carbonates (high Ca, Sr) enriched in C-13 and O-18, whereas rainfall in summer increases organic and clastic input (plagioclase, quartz) with high counts of lithogenic elements (K, Al, Ti, and Si). Eolian input of Ti occurs also in the dry season. Moving correlations (5-yr windows) of the Ca and Ti counts show similar development in both sequences until the 1930s. Positive correlations indicate mixing of allochthonous Ti and autochthonous Ca, while negative correlations indicate their separation in sublaminae. Negative excursions in the correlations correspond with historic and reconstructed droughts, El Nio events, and positive SST anomalies. Based on our data, droughts (3-7 year duration) were severe and centred around the following years: the early 1850s, 1865, 1880, 1895, 1905, 1915 and the late 1920s with continuation into the 1930s. The latter dry period brought both lake systems into a critical state making them susceptible to further drying. Groundwater overexploitation due to the expansion of irrigation agriculture in the region after 1940 induced the transition from calcite to aragonite precipitation in Alberca and halite infiltration in Rincn. The proxy data indicate a faster response to increased evaporation for Rincn, the lake with the larger maar dimensions, solar radiation receipt and higher conductivity, whereas the smaller, steeper Alberca maar responded rapidly to increased precipitation.},
  language  = {en}
}
@article{WolffKristenJennySchettleretal.2014,
  author    = {Wolff, Christian Michael and Kristen-Jenny, Iris and Schettler, Georg and Plessen, Birgit and Meyer, Hanno and Dulski, Peter and Naumann, Rudolf and Brauer, Achim and Verschuren, Dirk and Haug, Gerald H.},
  title     = {Modern seasonality in Lake Challa (Kenya/Tanzania) and its sedimentary documentation in recent lake sediments},
  series = {Limnology and oceanography},
  volume    = {59},
  journal   = {Limnology and oceanography},
  number    = {5},
  publisher = {Wiley},
  address   = {Waco},
  issn      = {0024-3590},
  doi       = {10.4319/lo.2014.59.5.1621},
  pages     = {1621 -- 1636},
  year      = {2014},
  abstract  = {From November 2006 to January 2010, a sediment trap that was cleared monthly was deployed in Lake Challa, a deep stratified freshwater lake on the eastern slope of Mt. Kilimanjaro in southern Kenya. Geochemical data from sediment trap samples were compared with a broad range of limnological and meteorological parameters to characterize the effect of single parameters on productivity and sedimentation processes in the crater basin. During the southern hemisphere summer (November-March), when the water temperature is high and the lake is biologically productive (nondiatom algae), calcite predominated in the sediment trap samples. During the "long rain" season (March-May) a small amount of organic matter and lithogenic material caused by rainfall appeared. This was followed by the cool and windy months of the southern hemisphere winter (June-October) when diatoms were the main component, indicating a diatom bloom initiated by improvement of nutrient availability related to upwelling processes. The sediment trap data support the hypothesis that the light-dark lamination couplets, which are abundant in Lake Challa cores, reflect seasonal delivery to the sediments of diatom-rich particulates during the windy months and diatom-poor material during the wet season. However, interannual and spatial variability in upwelling and productivity patterns, as well as El Nino-Southern Oscillation (ENSO)-related rainfall and drought cycles, exert a strong influence on the magnitude and geochemical composition of particle export to the hypolimnion of Lake Challa.},
  language  = {en}
}