TY  - JOUR
A1  - Serno, Sascha
A1  - Winckler, Gisela
A1  - Anderson, Robert F.
A1  - Jaccard, Samuel L.
A1  - Kienast, Stephanie S.
A1  - Haug, Gerald H.
T1  - Change in dust seasonality as the primary driver for orbital-scale dust storm variability in East Asia
JF  - Geophysical research letters
N2  - 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.
Y1  - 2017
U6  - https://doi.org/10.1002/2016GL072345
SN  - 0094-8276
SN  - 1944-8007
VL  - 44
SP  - 3796
EP  - 3805
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Lechleitner, Franziska A.
A1  - Breitenbach, Sebastian Franz Martin
A1  - Rehfeld, Kira
A1  - Ridley, Harriet E.
A1  - Asmerom, Yemane
A1  - Prufer, Keith M.
A1  - Marwan, Norbert
A1  - Goswami, Bedartha
A1  - Kennett, Douglas J.
A1  - Aquino, Valorie V.
A1  - Polyak, Victor
A1  - Haug, Gerald H.
A1  - Eglinton, Timothy I.
A1  - Baldini, James U. L.
T1  - Tropical rainfall over the last two millennia: evidence for a low-latitude hydrologic seesaw
JF  - Scientific reports
N2  - 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.
Y1  - 2017
U6  - https://doi.org/10.1038/srep45809
SN  - 2045-2322
VL  - 7
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Serno, Sascha
A1  - Winckler, Gisela
A1  - Anderson, Robert F.
A1  - Maier, Edith
A1  - Ren, Haojia
A1  - Gersonde, Rainer
A1  - Haug, Gerald H.
T1  - Comparing dust flux records from the Subarctic North Pacific and Greenland: Implications for atmospheric transport to Greenland and for the application of dust as a chronostratigraphic tool
JF  - Paleoceanography
N2  - We present a new record of eolian dust flux to the western Subarctic North Pacific (SNP) covering the past 27,000years based on a core from the Detroit Seamount. Comparing the SNP dust record to the North Greenland Ice Core Project (NGRIP) ice core record shows significant differences in the amplitude of dust changes to the two regions during the last deglaciation, while the timing of abrupt changes is synchronous. If dust deposition in the SNP faithfully records its mobilization in East Asian source regions, then the difference in the relative amplitude must reflect climate-related changes in atmospheric dust transport to Greenland. Based on the synchronicity in the timing of dust changes in the SNP and Greenland, we tie abrupt deglacial transitions in the Th-230-normalized He-4 flux record to corresponding transitions in the well-dated NGRIP dust flux record to provide a new chronostratigraphic technique for marine sediments from the SNP. Results from this technique are complemented by radiocarbon dating, which allows us to independently constrain radiocarbon paleoreservoir ages. We find paleoreservoir ages of 745140years at 11,653year B.P., 680228years at 14,630year B.P., and 790498years at 23,290year B.P. Our reconstructed paleoreservoir ages are consistent with modern surface water reservoir ages in the western SNP. Good temporal synchronicity between eolian dust records from the Subantarctic Atlantic and equatorial Pacific and the ice core record from Antarctica supports the reliability of the proposed dust tuning method to be used more widely in other global ocean regions.
KW  - Subarctic North Pacific
KW  - eolian dust
KW  - helium-4
KW  - atmospheric circulation
KW  - chronostratigrapy
KW  - paleoreservoir age
Y1  - 2015
U6  - https://doi.org/10.1002/2014PA002748
SN  - 0883-8305
SN  - 1944-9186
VL  - 30
IS  - 6
SP  - 583
EP  - 600
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Ren, Haojia
A1  - Studer, Anja S.
A1  - Serno, Sascha
A1  - Sigman, Daniel M.
A1  - Winckler, Gisela
A1  - Anderson, Robert F.
A1  - Oleynik, Sergey
A1  - Gersonde, Rainer
A1  - Haug, Gerald H.
T1  - Glacial-to-interglacial changes in nitrate supply and consumption in the subarctic North Pacific from microfossil-bound N isotopes at two trophic levels
JF  - Paleoceanography
N2  - Reduced nitrate supply to the subarctic North Pacific (SNP) surface during the last ice age has been inferred from coupled changes in diatom-bound delta N-15 (DB-delta N-15), bulk sedimentary delta N-15, and biogenic fluxes. However, the reliability of bulk sedimentary and DB-delta N-15 has been questioned, and a previously reported delta N-15 minimum during Heinrich Stadial 1 (HS1) has proven difficult to explain. In a core from the western SNP, we report the foraminifera-bound delta N-15 (FB-delta N-15) in Neogloboquadrina pachyderma and Globigerina bulloides, comparing them with DB-delta N-15 in the same core over the past 25 kyr. The delta N-15 of all recorders is higher during the Last Glacial Maximum (LGM) than in the Holocene, indicating more complete nitrate consumption. N. pachyderma FB-delta N-15 is similar to DB-delta N-15 in the Holocene but 2.2% higher during the LGM. This difference suggests a greater sensitivity of FB-delta(15)NZ to changes in summertime nitrate drawdown and delta N-15 rise, consistent with a lag of the foraminifera relative to diatoms in reaching their summertime production peak in this highly seasonal environment. Unlike DB-delta N-15, FB-delta N-15 does not decrease from the LGM into HS1, which supports a previous suggestion that the HS1 DB-delta N-15 minimum is due to contamination by sponge spicules. FB-delta N-15 drops in the latter half of the Bolling/Allerod warm period and rises briefly in the Younger Dryas cold period, followed by a decline into the mid-Holocene. The FB-delta N-15 records suggest that the coupling among cold climate, reduced nitrate supply, and more complete nitrate consumption that characterized the LGM also applied to the deglacial cold events.
Y1  - 2015
U6  - https://doi.org/10.1002/2014PA002765
SN  - 0883-8305
SN  - 1944-9186
VL  - 30
IS  - 9
SP  - 1217
EP  - 1232
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Wolff, Christian Michael
A1  - Kristen-Jenny, Iris
A1  - Schettler, Georg
A1  - Plessen, Birgit
A1  - Meyer, Hanno
A1  - Dulski, Peter
A1  - Naumann, Rudolf
A1  - Brauer, Achim
A1  - Verschuren, Dirk
A1  - Haug, Gerald H.
T1  - Modern seasonality in Lake Challa (Kenya/Tanzania) and its sedimentary documentation in recent lake sediments
JF  - Limnology and oceanography
N2  - 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.
Y1  - 2014
U6  - https://doi.org/10.4319/lo.2014.59.5.1621
SN  - 0024-3590
SN  - 1939-5590
VL  - 59
IS  - 5
SP  - 1621
EP  - 1636
PB  - Wiley
CY  - Waco
ER  - 
TY  - JOUR
A1  - Deplazes, Gaudenz
A1  - Lückge, Andreas
A1  - Stuut, Jan-Berend W.
A1  - Paetzold, Jürgen
A1  - Kuhlmann, Holger
A1  - Husson, Dorothee
A1  - Fant, Mara
A1  - Haug, Gerald H.
T1  - Weakening and strengthening of the Indian monsoon during Heinrich events and Dansgaard- Oeschger oscillations
JF  - Paleoceanography
N2  - The Dansgaard-Oeschger oscillations and Heinrich events described in North Atlantic sediments and Greenland ice are expressed in the climate of the tropics, for example, as documented in Arabian Sea sediments. Given the strength of this teleconnection, we seek to reconstruct its range of environmental impacts. We present geochemical and sedimentological data from core SO130-289KL from the Indus submarine slope spanning the last similar to 80 kyr. Elemental and grain size analyses consistently indicate that interstadials are characterized by an increased contribution of fluvial suspension from the Indus River. In contrast, stadials are characterized by an increased contribution of aeolian dust from the Arabian Peninsula. Decadal-scale shifts at climate transitions, such as onsets of interstadials, were coeval with changes in productivity-related proxies. Heinrich events stand out as especially dry and dusty events, indicating a dramatically weakened Indian summer monsoon, potentially increased winter monsoon circulation, and increased aridity on the Arabian Peninsula. This finding is consistent with other paleoclimate evidence for continental aridity in the northern tropics during these events. Our results strengthen the evidence that circum-North Atlantic temperature variations translate to hydrological shifts in the tropics, with major impacts on regional environmental conditions such as rainfall, river discharge, aeolian dust transport, and ocean margin anoxia.
KW  - Indian Monsoon
KW  - Arabian Sea
KW  - XRF
KW  - Dansgaard-Oeschger oscillations
KW  - Heinrich events
KW  - Sediment Transport
Y1  - 2014
U6  - https://doi.org/10.1002/2013PA002509
SN  - 0883-8305
SN  - 1944-9186
VL  - 29
IS  - 2
SP  - 99
EP  - 114
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Serno, Sascha
A1  - Winckler, Gisela
A1  - Anderson, Robert F.
A1  - Hayes, Christopher T.
A1  - McGee, David
A1  - Machalett, Bjoern
A1  - Ren, Haojia
A1  - Straub, Susanne M.
A1  - Gersonde, Rainer
A1  - Haug, Gerald H.
T1  - Eolian dust input to the Subarctic North Pacific
JF  - Earth & planetary science letters
N2  - Eolian dust is a significant source of iron and other nutrients that are essential for the health of marine ecosystems and potentially a controlling factor of the high nutrient-low chlorophyll status of the Subarctic North Pacific. We map the spatial distribution of dust input using three different geochemical tracers of eolian dust, He-4, Th-232 and rare earth elements, in combination with grain size distribution data, from a set of core-top sediments covering the entire Subarctic North Pacific. Using the suite of geochemical proxies to fingerprint different lithogenic components, we deconvolve eolian dust input from other lithogenic inputs such as volcanic ash, ice-rafted debris, riverine and hemipelagic input. While the open ocean sites far away from the volcanic arcs are dominantly composed of pure eolian dust, lithogenic components other than eolian dust play a more crucial role along the arcs. In sites dominated by dust, eolian dust input appears to be characterized by a nearly uniform grain size mode at similar to 4 mu m.
 Applying the Th-230-normalization technique, our proxies yield a consistent pattern of uniform dust fluxes of 1-2 g/m(2)/yr across the Subarctic North Pacific. Elevated eolian dust fluxes of 2-4 g/m(2)/yr characterize the westernmost region off Japan and the southern Kurile Islands south of 45 degrees N and west of 165 degrees E along the main pathway of the westerly winds. The core-top based dust flux reconstruction is consistent with recent estimates based on dissolved thorium isotope concentrations in seawater from the Subarctic North Pacific. The dust flux pattern compares well with state-of-the-art dust model predictions in the western and central Subarctic North Pacific, but we find that dust fluxes are higher than modeled fluxes by 0.5-1 g/m(2)/yr in the northwest, northeast and eastern Subarctic North Pacific. Our results provide an important benchmark for biogeochemical models and a robust approach for downcore studies testing dust-induced iron fertilization of past changes in biological productivity in the Subarctic North Pacific.
KW  - eolian dust
KW  - Subarctic North Pacific
KW  - INOPEX
KW  - helium-4
KW  - Th-232
KW  - REE
Y1  - 2014
U6  - https://doi.org/10.1016/j.epsl.2013.11.008
SN  - 0012-821X
SN  - 1385-013X
VL  - 387
SP  - 252
EP  - 263
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Serno, Sascha
A1  - Winckler, Gisela
A1  - Anderson, Robert F.
A1  - Hayes, Christopher T.
A1  - Ren, Haojia
A1  - Gersonde, Rainer
A1  - Haug, Gerald H.
T1  - Using the natural spatial pattern of marine productivity in the Subarctic North Pacific to evaluate paleoproductivity proxies
JF  - Paleoceanography
N2  - 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.
Y1  - 2014
U6  - https://doi.org/10.1002/2013PA002594
SN  - 0883-8305
SN  - 1944-9186
VL  - 29
IS  - 5
SP  - 438
EP  - 453
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Deplazes, Gaudenz
A1  - Lueckge, Andreas
A1  - Peterson, Larry C.
A1  - Timmermann, Axel
A1  - Hamann, Yvonne
A1  - Hughen, Konrad A.
A1  - Roehl, Ursula
A1  - Laj, Carlo
A1  - Cane, Mark A.
A1  - Sigman, Daniel M.
A1  - Haug, Gerald H.
T1  - Links between tropical rainfall and North Atlantic climate during the last glacial period
JF  - Nature geoscience
N2  - During the last glacial period, the North Atlantic region experienced pronounced, millennial-scale alternations between cold, stadial conditions and milder interstadial conditions-commonly referred to as Dansgaard-Oeschger oscillations-as well as periods of massive iceberg discharge known as Heinrich events(1). Changes in Northern Hemisphere temperature, as recorded in Greenland(2-4), are thought to have affected the location of the Atlantic intertropical convergence zone(5,6) and the strength of the Indian summer monsoon(7,8). Here we use high-resolution records of sediment colour-a measure of terrigenous versus biogenic content-from the Cariaco Basin off the coast of Venezuela and the Arabian Sea to assess teleconnections with the North Atlantic climate system during the last glacial period. The Cariaco record indicates that the intertropical convergence zone migrated seasonally over the site during mild stadial conditions, but was permanently displaced south of the basin during peak stadials and Heinrich events. In the Arabian Sea, we find evidence of a weak Indian summer monsoon during the stadial events. The tropical records show a more variable response to North Atlantic cooling than the Greenland temperature records. We therefore suggest that Greenland climate is especially sensitive to variations in the North Atlantic system-in particular sea-ice extent-whereas the intertropical convergence zone and Indian monsoon system respond primarily to variations in mean Northern Hemisphere temperature.
Y1  - 2013
U6  - https://doi.org/10.1038/ngeo1712
SN  - 1752-0894
VL  - 6
IS  - 3
SP  - 213
EP  - 217
PB  - Nature Publ. Group
CY  - New York
ER  - 
TY  - JOUR
A1  - Kienel, Ulrike
A1  - Plessen, Birgit
A1  - Schettler, Georg
A1  - Weise, Stephan
A1  - Pinkerneil, Sylvia
A1  - Boehnel, Harald
A1  - Englebrecht, Amy C.
A1  - Haug, Gerald H.
T1  - Sensitivity of a hypersaline crater lake to the seasonality of rainfall, evaporation, and guano supply
JF  - Fundamental and applied limnology : official journal of the International Association of Theoretical and Applied Limnology
N2  - The hypersaline crater lake and its catchment on seabird island Isabel (Pacific, off Mexico) was studied to explore the influence of strong seasonal variations in rainfall/evaporation and guano contribution on its limnology. The hypersaline lake water (HSW, 78 %) is up to 2.2-times enriched in inert ions relative to mean seawater. Rainfall during summer dilutes the HSW to form a less saline rainwater body (RWB) above a chemolimnion between 2 and 4 m water depth. The RWB is inhabited first by diatoms and ostracods followed later on by cyanobacteria and ciliates. Evaporation of > 1.5 m depth of lake water over the dry season increases the salinity of the RWB until the water column becomes isohaline at HSW concentrations in the late dry season. Differences in the stable isotope composition of water and primary producers in RWB and HSW reflect this development. Introduction of seabird guano and the decrease of salinity fuel a high primary production in the RWB with higher delta(CDIC)-C-13 and delta(13)Corg of particulate organic matter than in the HSW. The high N supply leads to high delta N-15 NH4 values (+ 39 % in the HSW) as the consequence of ammonia volatilization that is strongest during guano maturation and with evaporative salinity increase from the HSW. Precipitation of carbonate (calcite and aragonite) from the RWB and the HSW is hindered by the high concentration of guano-derived P. This inhibition may be overcome with evaporative supersaturation during particularly dry conditions. Carbonate may also precipitate during particularly wet conditions from the dilute RWB, where the P-concentration is reduced during an active phytoplankton production that raises the pH. Differences in the stable isotope signatures of carbon and oxygen in HSW and RWB (+ 5 % delta(CDIC)-C-13 and -3 % d18OH2O) suggest the processes of carbonate precipitation can be distinguished based on the isotope signature of the carbonates deposited. Changes in the lake system are indicated when lower temperatures and higher rainfall in the 2006 wet season introduced more and less mature guano to the lake. The lower pH was accompanied by lower ammonia volatilization and carbonate precipitation as indicated by an increased concentration of NH4, Ca, Sr and DIC, while delta H-2, delta(NNH4)-N-15, and salinity were lower. According to our results, the observed sediment laminations should reflect the introduction of catchment material (including guano) with runoff, the RWB plankton production, and the carbonate precipitation in relation to its origin and seasonality.
KW  - ammonia volatilization
KW  - carbonate precipitation
KW  - chemocline
KW  - guano
KW  - hypersaline lake
KW  - stable isotopes
Y1  - 2013
U6  - https://doi.org/10.1127/1863-9135/2013/0405
SN  - 1863-9135
VL  - 183
IS  - 2
SP  - 135
EP  - 152
PB  - Schweizerbart
CY  - Stuttgart
ER  -