@article{MartinezGarciaRosellMeleJaccardetal.2011, author = {Martinez-Garcia, Alfredo and Rosell-Mele, Antoni and Jaccard, Samuel L. and Geibert, Walter and Sigman, Daniel M. and Haug, Gerald H.}, title = {Southern Ocean dust-climate coupling over the past four million years}, series = {Nature : the international weekly journal of science}, volume = {476}, journal = {Nature : the international weekly journal of science}, number = {7360}, publisher = {Nature Publ. Group}, address = {London}, issn = {0028-0836}, doi = {10.1038/nature10310}, pages = {312 -- U141}, year = {2011}, abstract = {Dust has the potential to modify global climate by influencing the radiative balance of the atmosphere and by supplying iron and other essential limiting micronutrients to the ocean(1,2). Indeed, dust supply to the Southern Ocean increases during ice ages, and 'iron fertilization' of the subantarctic zone may have contributed up to 40 parts per million by volume (p. p. m. v.) of the decrease (80-100 p. p. m. v.) in atmospheric carbon dioxide observed during late Pleistocene glacial cycles(3-7). So far, however, the magnitude of Southern Ocean dust deposition in earlier times and its role in the development and evolution of Pleistocene glacial cycles have remained unclear. Here we report a high-resolution record of dust and iron supply to the Southern Ocean over the past four million years, derived from the analysis of marine sediments from ODP Site 1090, located in the Atlantic sector of the subantarctic zone. The close correspondence of our dust and iron deposition records with Antarctic ice core reconstructions of dust flux covering the past 800,000 years (refs 8, 9) indicates that both of these archives record large-scale deposition changes that should apply to most of the Southern Ocean, validating previous interpretations of the ice core data. The extension of the record beyond the interval covered by the Antarctic ice cores reveals that, in contrast to the relatively gradual intensification of glacial cycles over the past three million years, Southern Ocean dust and iron flux rose sharply at the Mid-Pleistocene climatic transition around 1.25 million years ago. This finding complements previous observations over late Pleistocene glacial cycles(5,8,9), providing new evidence of a tight connection between high dust input to the Southern Ocean and the emergence of the deep glaciations that characterize the past one million years of Earth history.}, language = {en} } @article{WolffHaugTimmermannetal.2011, author = {Wolff, Christian Michael and Haug, Gerald H. and Timmermann, Axel and Damste, Jaap S. Sinninghe and Brauer, Achim and Sigman, Daniel M. and Cane, Mark A. and Verschuren, Dirk}, title = {Reduced interannual rainfall variability in East Africa during the last Ice Age}, series = {Science}, volume = {333}, journal = {Science}, number = {6043}, publisher = {American Assoc. for the Advancement of Science}, address = {Washington}, issn = {0036-8075}, doi = {10.1126/science.1203724}, pages = {743 -- 747}, year = {2011}, abstract = {Interannual rainfall variations in equatorial East Africa are tightly linked to the El Nino Southern Oscillation (ENSO), with more rain and flooding during El Nino and droughts in La Nina years, both having severe impacts on human habitation and food security. Here we report evidence from an annually laminated lake sediment record from southeastern Kenya for interannual to centennial-scale changes in ENSO-related rainfall variability during the last three millennia and for reductions in both the mean rate and the variability of rainfall in East Africa during the Last Glacial period. Climate model simulations support forward extrapolation from these lake sediment data that future warming will intensify the interannual variability of East Africa's rainfall.}, language = {en} } @article{HainSigmanHaug2011, author = {Hain, Mathis P. and Sigman, Daniel M. and Haug, Gerald H.}, title = {Shortcomings of the isolated abyssal reservoir model for deglacial radiocarbon changes in the mid-depth Indo-Pacific Ocean}, series = {Geophysical research letters}, volume = {38}, journal = {Geophysical research letters}, number = {6}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1029/2010GL046158}, pages = {6}, year = {2011}, abstract = {Severely negative Delta(14)C anomalies from the mid-depth Pacific and the Arabian Sea have been taken as support for the hypothesized deglacial release of a previously isolated, extremely (14)C-deplete deep ocean carbon reservoir. We report box model simulations that cast doubt on both the existence of the hypothesized deep reservoir and its ability to explain the mid-depth Delta(14)C anomalies. First, the degree of ice age isolation needed to substantially reduce the deep Delta(14)C of the deep reservoir causes anoxia and the trapping of alkalinity from CaCO(3) dissolution, the latter increasing atmospheric CO(2). Second, even with a completely (14)C-free deep reservoir, achieving the mid-depth Delta(14)C anomalies of observed duration requires ad hoc stifling of aspects of deep circulation to prevent rapid dissipation of the anomalous (14)C-free carbon to the rest of the ocean and the atmosphere. We suggest that the mid-depth anomalies do not record basin-scale Delta(14)C changes but are instead local phenomena.}, language = {en} } @article{StuderMartinezGarciaJaccardetal.2012, author = {Studer, Anja S. and Martinez-Garcia, Alfredo and Jaccard, Samuel L. and Girault, France E. and Sigman, Daniel M. and Haug, Gerald H.}, title = {Enhanced stratification and seasonality in the Subarctic Pacific upon Northern Hemisphere Glaciation-New evidence from diatom-bound nitrogen isotopes, alkenones and archaeal tetraethers}, series = {Earth \& planetary science letters}, volume = {351}, journal = {Earth \& planetary science letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2012.07.029}, pages = {84 -- 94}, year = {2012}, abstract = {Coincident with the intensification of Northern Hemisphere Glaciation (WIG) around 2.73 million years (Ma) ago, sediment cores from both the open subarctic North Pacific and the Antarctic indicate a rapid decline in diatom opal accumulation flux to the seabed, representing one of the most abrupt and dramatic changes in the marine sediment record associated with the development of Pleistocene glacial cycles. In the North Pacific, bulk sediment nitrogen isotope data and alkenone-derived sea surface temperature (SST) estimates suggest that the productivity decline was driven by reduced exchange between surface and deep water, due to weaker wind-driven upwelling and/or a strengthening of the halocline (i.e. "stratification"). In this study of the 2.73 Ma transition at Ocean Drilling Program (ODP) Site 882 in the western subarctic North Pacific, diatom-bound nitrogen isotopes (delta N-15(db)), alkenone mass accumulation rate, and alkenone- and archaeal tetraether-based SST reconstructions support the stratification hypothesis, indicating perennially lower export production, generally higher nitrate consumption, and greater inter-seasonal variation in SST after the 2.73 Ma transition. In addition, the delta N-15(db) of large and small size fractions of Coscinodiscus spp. suggest that these diatoms grew mostly during the spring bloom during the late Pliocene, switching to their current fall-to-winter growth period at the 2.73 Ma transition; this view is consistent with their decline in dominance and provides further evidence for increased stratification (reduced vertical exchange) in the North Pacific after 2.73 Ma. The delta N-15(db) data indicate that, over the similar to 100 kyr period after the 2.73 Ma transition studied here, nitrate consumption did not reach late Pleistocene ice age levels and that nitrate consumption in post-2.73 Ma warm stages was similar to that before the transition, even though productivity was greatly reduced. We tentatively attribute this to relatively weak dust-borne iron inputs in the early post-2.73 Ma period.}, language = {en} } @article{SernoWincklerAndersonetal.2014, author = {Serno, Sascha and Winckler, Gisela and Anderson, Robert F. and Hayes, Christopher T. and Ren, Haojia and Gersonde, Rainer and Haug, Gerald H.}, title = {Using the natural spatial pattern of marine productivity in the Subarctic North Pacific to evaluate paleoproductivity proxies}, series = {Paleoceanography}, volume = {29}, journal = {Paleoceanography}, number = {5}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0883-8305}, doi = {10.1002/2013PA002594}, pages = {438 -- 453}, year = {2014}, abstract = {Sedimentary proxies used to reconstruct marine productivity suffer from variable preservation and are sensitive to factors other than productivity. Therefore, proxy calibration is warranted. Here we map the spatial patterns of two paleoproductivity proxies, biogenic opal and barium fluxes, from a set of core-top sediments recovered in the Subarctic North Pacific. Comparisons of the proxy data with independent estimates of primary and export production, surface water macronutrient concentrations, and biological pCO(2) drawdown indicate that neither proxy shows a significant correlation with primary or export productivity for the entire region. Biogenic opal fluxes, when corrected for preservation using Th-230-normalized accumulation rates, show a good correlation with primary productivity along the volcanic arcs (tau = 0.71, p = 0.0024) and with export productivity throughout the western Subarctic North Pacific (tau = 0.71, p = 0.0107). Moderate and good correlations of biogenic barium flux with export production (tau = 0.57, p = 0.0022) and with surface water silicate concentrations (tau = 0.70, p = 0.0002) are observed for the central and eastern Subarctic North Pacific. For reasons unknown, however, no correlation is found in the western Subarctic North Pacific between biogenic barium flux and the reference data. Nonetheless, we show that barite saturation, uncertainty in the lithogenic barium corrections, and problems with the reference data sets are not responsible for the lack of a significant correlation between biogenic barium flux and the reference data. Further studies evaluating the factors controlling the variability of the biogenic constituents in the sediments are desirable in this region.}, language = {en} } @misc{SernoWincklerAndersonetal.2017, author = {Serno, Sascha and Winckler, Gisela and Anderson, Robert F. and Jaccard, Samuel L. and Kienast, Stephanie S. and Haug, Gerald H.}, title = {Change in dust seasonality as the primary driver for orbital-scale dust storm variability in East Asia}, series = {Geophysical research letters}, volume = {44}, journal = {Geophysical research letters}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1002/2016GL072345}, pages = {3796 -- 3805}, year = {2017}, abstract = {Glacial periods are recognized to be dustier than interglacials, but the conditions leading to greater dust mobilization are poorly defined. Here we present a new high-resolution dust record based on Th-230-normalized He-4 flux from Ocean Drilling Program site 882 in the Subarctic North Pacific covering the last 170,000years. By analogy with modern relationships, we infer the mechanisms controlling orbital-scale dust storm variability in East Asia. We propose that orbital-scale dust flux variability is the result of an expansion of the dust season into summer, in addition to more intense dust storms during spring and fall. The primary drivers influencing dust flux include summer insolation at subarctic latitudes and variable Siberian alpine glaciation, which together control the cold air reservoir in Siberia. Changes in the extent of the Northern Hemisphere ice sheets may be a secondary control.}, language = {en} } @article{NaafsHefterActonetal.2012, author = {Naafs, B. David A. and Hefter, Jens and Acton, Gary and Haug, Gerald H. and Martinez-Garcia, Alfredo and Pancost, Richard and Stein, R{\"u}diger}, title = {Strengthening of North American dust sources during the late Pliocene (2.7 Ma)}, series = {Earth \& planetary science letters}, volume = {317}, journal = {Earth \& planetary science letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2011.11.026}, pages = {8 -- 19}, year = {2012}, abstract = {Here we present orbitally-resolved records of terrestrial higher plant leaf wax input to the North Atlantic over the last 3.5 Ma, based on the accumulation of long-chain n-alkanes and n-alkanl-1-ols at IODP Site U1313. These lipids are a major component of dust, even in remote ocean areas, and have a predominantly aeolian origin in distal marine sediments. Our results demonstrate that around 2.7 million years ago (Ma), coinciding with the intensification of the Northern Hemisphere glaciation (NHG), the aeolian input of terrestrial material to the North Atlantic increased drastically. Since then, during every glacial the aeolian input of higher plant material was up to 30 times higher than during interglacials. The close correspondence between aeolian input to the North Atlantic and other dust records indicates a globally uniform response of dust sources to Quaternary climate variability, although the amplitude of variation differs among areas. We argue that the increased aeolian input at Site U1313 during glacials is predominantly related to the episodic appearance of continental ice sheets in North America and the associated strengthening of glaciogenic dust sources. Evolutional spectral analyses of the n-alkane records were therefore used to determine the dominant astronomical forcing in North American ice sheet advances. These results demonstrate that during the early Pleistocene North American ice sheet dynamics responded predominantly to variations in obliquity (41 ka), which argues against previous suggestions of precession-related variations in Northern Hemisphere ice sheets during the early Pleistocene.}, language = {en} } @article{NaafsHefterFerrettietal.2011, author = {Naafs, B. David A. and Hefter, Jens and Ferretti, Patrizia and Stein, R{\"u}diger and Haug, Gerald H.}, title = {Sea surface temperatures did not control the first occurrence of Hudson Strait Heinrich Events during MIS 16}, series = {Paleoceanography}, volume = {26}, journal = {Paleoceanography}, number = {4}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0883-8305}, doi = {10.1029/2011PA002135}, pages = {10}, year = {2011}, abstract = {Hudson Strait (HS) Heinrich Events, ice-rafting events in the North Atlantic originating from the Laurentide ice sheet (LIS), are among the most dramatic examples of millennial-scale climate variability and have a large influence on global climate. However, it is debated as to whether the occurrence of HS Heinrich Events in the (eastern) North Atlantic in the geological record depends on greater ice discharge, or simply from the longer survival of icebergs in cold waters. Using sediments from Integrated Ocean Drilling Program (IODP) Site U1313 in the North Atlantic spanning the period between 960 and 320 ka, we show that sea surface temperatures (SSTs) did not control the first occurrence of HS Heinrich(-like) Events in the sedimentary record. Using mineralogy and organic geochemistry to determine the characteristics of ice-rafting debris (IRD), we detect the first HS Heinrich(-like) Event in our record around 643 ka (Marine Isotope Stage (MIS) 16), which is similar as previously reported for Site U1308. However, the accompanying high-resolution alkenone-based SST record demonstrates that the first HS Heinrich(-like) Event did not coincide with low SSTs. Thus, the HS Heinrich(-like) Events do indicate enhanced ice discharge from the LIS at the end of the Mid-Pleistocene Transition, not simply the survivability of icebergs due to cold conditions in the North Atlantic.}, language = {en} } @article{BreitenbachAdkinsMeyeretal.2010, author = {Breitenbach, Sebastian Franz Martin and Adkins, Jess F. and Meyer, Hanno and Marwan, Norbert and Kumar, Kanikicharla Krishna and Haug, Gerald H.}, title = {Strong influence of water vapor source dynamics on stable isotopes in precipitation observed in Southern Meghalaya, NE India}, issn = {0012-821X}, doi = {10.1016/j.epsl.2010.01.038}, year = {2010}, abstract = {To calibrate delta O-18 time-series from speleothems in the eastern Indian summer monsoon (ISM) region of India, and to understand the moisture regime over the northern Bay of Bengal (BoB) we analyze the delta O-18 and delta D of rainwater, collected in 2007 and 2008 near Cherrapunji, India. delta D values range from + 18.5 parts per thousand to 144.4 parts per thousand, while delta O-18 varies between +0.8 parts per thousand and 18.8 parts per thousand. The Local Meteoric Water Line (LMWL) is found to be indistinguishable from the Global Meteoric Water Line (GMWL). Late ISM (September-October) rainfall exhibits lowest delta O-18 and delta D values, with little relationship to the local precipitation amount. There is a trend to lighter isotope values over the course of the ISM, but it does not correlate with the patterns of temperature and rainfall amount delta O-18 and delta D time-series have to be interpreted with caution in terms of the 'amount effect' in this subtropical region. We find that the temporal trend in delta O-18 reflects increasing transport distance during the ISM, isotopic changes in the northern BoB surface waters during late ISM, and vapor re-equilibration with rain droplets. Using an isotope box model for surface ocean waters, we quantify the potential influence of river runoff on the isotopic composition of the seasonal freshwater plume in the northern BoB. Temporal variations in this source can contribute up to 25\% of the observed changes in stable isotopes of precipitation in NE India. To delineate other moisture sources, we use backward trajectory computations and find a strong correlation between source region and isotopic composition. Palaeoclimatic stable isotope time-series from northeast Indian speleothems likely reflect changes in moisture source and transport pathway, as well as the isotopic composition of the BoB surface water, all of which in turn reflect ISM strength. Stalagmite records from the region can therefore be interpreted as integrated measures of the ISM strength.}, language = {en} } @article{LechleitnerBreitenbachRehfeldetal.2017, author = {Lechleitner, Franziska A. and Breitenbach, Sebastian Franz Martin and Rehfeld, Kira and Ridley, Harriet E. and Asmerom, Yemane and Prufer, Keith M. and Marwan, Norbert and Goswami, Bedartha and Kennett, Douglas J. and Aquino, Valorie V. and Polyak, Victor and Haug, Gerald H. and Eglinton, Timothy I. and Baldini, James U. L.}, title = {Tropical rainfall over the last two millennia: evidence for a low-latitude hydrologic seesaw}, series = {Scientific reports}, volume = {7}, journal = {Scientific reports}, publisher = {Nature Publ. Group}, address = {London}, issn = {2045-2322}, doi = {10.1038/srep45809}, pages = {9}, year = {2017}, abstract = {The presence of a low-to mid-latitude interhemispheric hydrologic seesaw is apparent over orbital and glacial-interglacial timescales, but its existence over the most recent past remains unclear. Here we investigate, based on climate proxy reconstructions from both hemispheres, the inter-hemispherical phasing of the Intertropical Convergence Zone (ITCZ) and the low-to mid-latitude teleconnections in the Northern Hemisphere over the past 2000 years. A clear feature is a persistent southward shift of the ITCZ during the Little Ice Age until the beginning of the 19th Century. Strong covariation between our new composite ITCZ-stack and North Atlantic Oscillation (NAO) records reveals a tight coupling between these two synoptic weather and climate phenomena over decadal-to-centennial timescales. This relationship becomes most apparent when comparing two precisely dated, high-resolution paleorainfall records from Belize and Scotland, indicating that the low-to mid-latitude teleconnection was also active over annual-decadal timescales. It is likely a combination of external forcing, i.e., solar and volcanic, and internal feedbacks, that drives the synchronous ITCZ and NAO shifts via energy flux perturbations in the tropics.}, language = {en} }