TY  - JOUR
A1  - Schewe, Jacob
A1  - Levermann, Anders
A1  - Cheng, Hai
T1  - A critical humidity threshold for monsoon transitions
JF  - Climate of the past : an interactive open access journal of the European Geosciences Union
N2  - Monsoon systems around the world are governed by the so-called moisture-advection feedback. Here we show that, in a minimal conceptual model, this feedback implies a critical threshold with respect to the atmospheric specific humidity q(o) over the ocean adjacent to the monsoon region. If q(o) falls short of this critical value q(o)(c), monsoon rainfall over land cannot be sustained. Such a case could occur if evaporation from the ocean was reduced, e.g. due to low sea surface temperatures. Within the restrictions of the conceptual model, we estimate q(o)(c) from present-day reanalysis data for four major monsoon systems, and demonstrate how this concept can help understand abrupt variations in monsoon strength on orbital timescales as found in proxy records.
Y1  - 2012
U6  - https://doi.org/10.5194/cp-8-535-2012
SN  - 1814-9324
VL  - 8
IS  - 2
SP  - 535
EP  - 544
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Lechleitner, Franziska A.
A1  - Breitenbach, Sebastian Franz Martin
A1  - Cheng, Hai
A1  - Plessen, Birgit
A1  - Rehfeld, Kira
A1  - Goswami, Bedartha
A1  - Marwan, Norbert
A1  - Eroglu, Deniz
A1  - Adkins, Jess F.
A1  - Haug, Gerald
T1  - Climatic and in-cave influences on delta O-18 and delta C-13 in a stalagmite from northeastern India through the last deglaciation
JF  - Quaternary research : an interdisciplinary journal
N2  - Northeastern (NE) India experiences extraordinarily pronounced seasonal climate, governed by the Indian summer monsoon (ISM). The vulnerability of this region to floods and droughts calls for detailed and highly resolved paleoclimate reconstructions to assess the recurrence rate and driving factors of ISM changes. We use stable oxygen and carbon isotope ratios (delta O-18 and delta C-13) from stalagmite MAW-6 from Mawmluh Cave to infer climate and environmental conditions in NE India over the last deglaciation (16-6ka). We interpret stalagmite delta O-18 as reflecting ISM strength, whereas delta C-13 appears to be driven by local hydroclimate conditions. Pronounced shifts in ISM strength over the deglaciation are apparent from the delta O-18 record, similarly to other records from monsoonal Asia. The ISM is weaker during the late glacial (LG) period and the Younger Dryas, and stronger during the BOlling-Allerod and Holocene. Local conditions inferred from the delta C-13 record appear to have changed less substantially over time, possibly related to the masking effect of changing precipitation seasonality. Time series analysis of the delta O-18 record reveals more chaotic conditions during the late glacial and higher predictability during the Holocene, likely related to the strengthening of the seasonal recurrence of the ISM with the onset of the Holocene.
KW  - Indian Summer Monsoon
KW  - stalagmite
KW  - oxygen isotopes
KW  - carbon isotopes
KW  - deglaciation
Y1  - 2017
U6  - https://doi.org/10.1017/qua.2017.72
SN  - 0033-5894
SN  - 1096-0287
VL  - 88
SP  - 458
EP  - 471
PB  - Cambridge Univ. Press
CY  - New York
ER  - 
TY  - JOUR
A1  - Breitenbach, Sebastian Franz Martin
A1  - Rehfeld, Kira
A1  - Goswami, Bedartha
A1  - Baldini, James U. L.
A1  - Ridley, H. E.
A1  - Kennett, D. J.
A1  - Prufer, K. M.
A1  - Aquino, Valorie V.
A1  - Asmerom, Yemane
A1  - Polyak, V. J.
A1  - Cheng, Hai
A1  - Kurths, Jürgen
A1  - Marwan, Norbert
T1  - Constructing Proxy Records from Age models (COPRA)
JF  - Climate of the past : an interactive open access journal of the European Geosciences Union
N2  - Reliable age models are fundamental for any palaeoclimate reconstruction. Available interpolation procedures between age control points are often inadequately reported, and very few translate age uncertainties to proxy uncertainties. Most available modeling algorithms do not allow incorporation of layer counted intervals to improve the confidence limits of the age model in question.
 We present a framework that allows detection and interactive handling of age reversals and hiatuses, depth-age modeling, and proxy-record reconstruction. Monte Carlo simulation and a translation procedure are used to assign a precise time scale to climate proxies and to translate dating uncertainties to uncertainties in the proxy values. The presented framework allows integration of incremental relative dating information to improve the final age model. The free software package COPRA1.0 facilitates easy interactive usage.
Y1  - 2012
U6  - https://doi.org/10.5194/cp-8-1765-2012
SN  - 1814-9324
VL  - 8
IS  - 5
SP  - 1765
EP  - 1779
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Westphal, Niko
A1  - Charles, Christopher D.
A1  - Cobb, Kim M.
A1  - Cheng, Hai
A1  - Edwards, R. Lawrence
A1  - Haug, Gerald H.
T1  - ENSO record in mid-late Holocene fossil corals from Line Islands : forced response or internal variability?
Y1  - 2009
UR  - http://www.sciencedirect.com/science/journal/00167037
U6  - https://doi.org/10.1016/j.gca.2009.05.027
SN  - 0016-7037
ER  - 
TY  - JOUR
A1  - Comas-Bru, Laia
A1  - Harrison, Sandy P.
A1  - Werner, Martin
A1  - Rehfeld, Kira
A1  - Scroxton, Nick
A1  - Veiga-Pires, Cristina
A1  - Ahmad, Syed Masood
A1  - Brahim, Yassine Ait
A1  - Mozhdehi, Sahar Amirnezhad
A1  - Arienzo, Monica
A1  - Atsawawaranunt, Kamolphat
A1  - Baker, Andy
A1  - Braun, Kerstin
A1  - Breitenbach, Sebastian Franz Martin
A1  - Burstyn, Yuval
A1  - Chawchai, Sakonvan
A1  - Columbu, Andrea
A1  - Deininger, Michael
A1  - Demeny, Attila
A1  - Dixon, Bronwyn
A1  - Hatvani, Istvan Gabor
A1  - Hu, Jun
A1  - Kaushal, Nikita
A1  - Kern, Zoltan
A1  - Labuhn, Inga
A1  - Lachniet, Matthew S.
A1  - Lechleitner, Franziska A.
A1  - Lorrey, Andrew
A1  - Markowska, Monika
A1  - Nehme, Carole
A1  - Novello, Valdir F.
A1  - Oster, Jessica
A1  - Perez-Mejias, Carlos
A1  - Pickering, Robyn
A1  - Sekhon, Natasha
A1  - Wang, Xianfeng
A1  - Warken, Sophie
A1  - Atkinson, Tim
A1  - Ayalon, Avner
A1  - Baldini, James
A1  - Bar-Matthews, Miryam
A1  - Bernal, Juan Pablo
A1  - Boch, Ronny
A1  - Borsato, Andrea
A1  - Boyd, Meighan
A1  - Brierley, Chris
A1  - Cai, Yanjun
A1  - Carolin, Stacy
A1  - Cheng, Hai
A1  - Constantin, Silviu
A1  - Couchoud, Isabelle
A1  - Cruz, Francisco
A1  - Denniston, Rhawn
A1  - Dragusin, Virgil
A1  - Duan, Wuhui
A1  - Ersek, Vasile
A1  - Finne, Martin
A1  - Fleitmann, Dominik
A1  - Fohlmeister, Jens Bernd
A1  - Frappier, Amy
A1  - Genty, Dominique
A1  - Holzkamper, Steffen
A1  - Hopley, Philip
A1  - Johnston, Vanessa
A1  - Kathayat, Gayatri
A1  - Keenan-Jones, Duncan
A1  - Koltai, Gabriella
A1  - Li, Ting-Yong
A1  - Lone, Mahjoor Ahmad
A1  - Luetscher, Marc
A1  - Mattey, Dave
A1  - Moreno, Ana
A1  - Moseley, Gina
A1  - Psomiadis, David
A1  - Ruan, Jiaoyang
A1  - Scholz, Denis
A1  - Sha, Lijuan
A1  - Smith, Andrew Christopher
A1  - Strikis, Nicolas
A1  - Treble, Pauline
A1  - Unal-Imer, Ezgi
A1  - Vaks, Anton
A1  - Vansteenberge, Stef
A1  - Voarintsoa, Ny Riavo G.
A1  - Wong, Corinne
A1  - Wortham, Barbara
A1  - Wurtzel, Jennifer
A1  - Zhang, Haiwei
T1  - Evaluating model outputs using integrated global speleothem records of climate change since the last glacial
JF  - Climate of the past : an interactive open access journal of the European Geosciences Union
N2  - Although quantitative isotope data from speleothems has been used to evaluate isotope-enabled model simulations, currently no consensus exists regarding the most appropriate methodology through which to achieve this. A number of modelling groups will be running isotope-enabled palaeoclimate simulations in the framework of the Coupled Model Intercomparison Project Phase 6, so it is timely to evaluate different approaches to using the speleothem data for data–model comparisons. Here, we illustrate this using 456 globally distributed speleothem δ18O records from an updated version of the Speleothem Isotopes Synthesis and Analysis (SISAL) database and palaeoclimate simulations generated using the ECHAM5-wiso isotope-enabled atmospheric circulation model. We show that the SISAL records reproduce the first-order spatial patterns of isotopic variability in the modern day, strongly supporting the application of this dataset for evaluating model-derived isotope variability into the past. However, the discontinuous nature of many speleothem records complicates the process of procuring large numbers of records if data–model comparisons are made using the traditional approach of comparing anomalies between a control period and a given palaeoclimate experiment. To circumvent this issue, we illustrate techniques through which the absolute isotope values during any time period could be used for model evaluation. Specifically, we show that speleothem isotope records allow an assessment of a model's ability to simulate spatial isotopic trends. Our analyses provide a protocol for using speleothem isotope data for model evaluation, including screening the observations to take into account the impact of speleothem mineralogy on δ18O values, the optimum period for the modern observational baseline and the selection of an appropriate time window for creating means of the isotope data for palaeo-time-slices.
Y1  - 2019
U6  - https://doi.org/10.5194/cp-15-1557-2019
SN  - 1814-9324
SN  - 1814-9332
VL  - 15
IS  - 4
SP  - 1557
EP  - 1579
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Apaestegui, James
A1  - Cruz, Francisco William
A1  - Vuille, Mathias
A1  - Fohlmeister, Jens Bernd
A1  - Carlo Espinoza, Jhan
A1  - Sifeddine, Abdelfettah
A1  - Strikis, Nicolas
A1  - Guyot, Jean Loup
A1  - Ventura, Roberto
A1  - Cheng, Hai
A1  - Edwards, R. Lawrence
T1  - Precipitation changes over the eastern Bolivian Andes inferred from speleothem (delta O-18) records for the last 1400 years
JF  - Earth & planetary science letters
N2  - Here we present high-resolution delta O-18 records obtained from speleothems collected in the eastern Bolivian Andes. The stable isotope records are related to the regional- to large-scale atmospheric circulation over South America and allow interpreting changes in delta O-18 during the last 1400 yr as a function of changes in precipitation regimes over the southern tropical Andes. Two distinct phases with more negative delta O-18 values, interpreted as periods of increased convective activity over the eastern Andean Cordillera in Bolivia are observed concomitantly with periods of global climate anomalies during the last millennium, such as the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) respectively. Changes in the Bolivian delta O-18 record during the LIA are apparently related to a southward displacement of the Intertropical Convergence Zone (ITCZ), which acts as a main moisture driver to intensify convection over the tropical continent. During the MCA, however, the increased convective activity observed in the Bolivian record is likely the result of a different mechanism, which implies moisture sourced mainly from the southern tropical Atlantic. This interpretation is consistent with paleoclimate records further to the north in the tropical Andes that show progressively drier conditions during this time period, indicating a more northerly position of the ITCZ. The transition period between the MCA and the LIA shows a slight tendency toward increased delta O-18 values, indicating weakened convective activity. Our results also reveal a non-stationary anti-phased behavior between the delta O-18 reconstructions from Bolivia and northeastern Brazil that confirms a continental-scale east-west teleconnection across South America during the LIA.
KW  - speleothems
KW  - stable isotopes
KW  - MCA
KW  - LIA
KW  - Bolivia
KW  - South American Monsoon
Y1  - 2018
U6  - https://doi.org/10.1016/j.epsl.2018.04.048
SN  - 0012-821X
SN  - 1385-013X
VL  - 494
SP  - 124
EP  - 134
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Atsawawaranunt, Kamolphat
A1  - Comas-Bru, Laia
A1  - Mozhdehi, Sahar Amirnezhad
A1  - Deininger, Michael
A1  - Harrison, Sandy P.
A1  - Baker, Andy
A1  - Boyd, Meighan
A1  - Kaushal, Nikita
A1  - Ahmad, Syed Masood
A1  - Brahim, Yassine Ait
A1  - Arienzo, Monica
A1  - Bajo, Petra
A1  - Braun, Kerstin
A1  - Burstyn, Yuval
A1  - Chawchai, Sakonvan
A1  - Duan, Wuhui
A1  - Hatvani, Istvan Gabor
A1  - Hu, Jun
A1  - Kern, Zoltan
A1  - Labuhn, Inga
A1  - Lachniet, Matthew
A1  - Lechleitner, Franziska A.
A1  - Lorrey, Andrew
A1  - Perez-Mejias, Carlos
A1  - Pickering, Robyn
A1  - Scroxton, Nick
A1  - Atkinson, Tim
A1  - Ayalon, Avner
A1  - Baldini, James
A1  - Bar-Matthews, Miriam
A1  - Pablo Bernal, Juan
A1  - Breitenbach, Sebastian Franz Martin
A1  - Boch, Ronny
A1  - Borsato, Andrea
A1  - Cai, Yanjun
A1  - Carolin, Stacy
A1  - Cheng, Hai
A1  - Columbu, Andrea
A1  - Couchoud, Isabelle
A1  - Cruz, Francisco
A1  - Demeny, Attila
A1  - Dominguez-Villar, David
A1  - Dragusin, Virgil
A1  - Drysdale, Russell
A1  - Ersek, Vasile
A1  - Finne, Martin
A1  - Fleitmann, Dominik
A1  - Fohlmeister, Jens Bernd
A1  - Frappier, Amy
A1  - Genty, Dominique
A1  - Holzkamper, Steffen
A1  - Hopley, Philip
A1  - Kathayat, Gayatri
A1  - Keenan-Jones, Duncan
A1  - Koltai, Gabriella
A1  - Luetscher, Marc
A1  - Li, Ting-Yong
A1  - Lone, Mahjoor Ahmad
A1  - Markowska, Monika
A1  - Mattey, Dave
A1  - McDermott, Frank
A1  - Moreno, Ana
A1  - Moseley, Gina
A1  - Nehme, Carole
A1  - Novello, Valdir F.
A1  - Psomiadis, David
A1  - Rehfeld, Kira
A1  - Ruan, Jiaoyang
A1  - Sekhon, Natasha
A1  - Sha, Lijuan
A1  - Sholz, Denis
A1  - Shopov, Yavor
A1  - Smith, Andrew
A1  - Strikis, Nicolas
A1  - Treble, Pauline
A1  - Unal-Imer, Ezgi
A1  - Vaks, Anton
A1  - Vansteenberge, Stef
A1  - Veiga-Pires, Cristina
A1  - Voarintsoa, Ny Riavo
A1  - Wang, Xianfeng
A1  - Wong, Corinne
A1  - Wortham, Barbara
A1  - Wurtzel, Jennifer
A1  - Zong, Baoyun
T1  - The SISAL database
BT  - a global resource to document oxygen and carbon isotope records from speleothems
JF  - Earth System Science Data
N2  - Stable isotope records from speleothems provide information on past climate changes, most particularly information that can be used to reconstruct past changes in precipitation and atmospheric circulation. These records are increasingly being used to provide "out-of-sample" evaluations of isotope-enabled climate models. SISAL (Speleothem Isotope Synthesis and Analysis) is an international working group of the Past Global Changes (PAGES) project. The working group aims to provide a comprehensive compilation of speleothem isotope records for climate reconstruction and model evaluation. The SISAL database contains data for individual speleothems, grouped by cave system. Stable isotopes of oxygen and carbon (delta O-18, delta C-13) measurements are referenced by distance from the top or bottom of the speleothem. Additional tables provide information on dating, including information on the dates used to construct the original age model and sufficient information to assess the quality of each data set and to erect a standardized chronology across different speleothems. The metadata table provides location information, information on the full range of measurements carried out on each speleothem and information on the cave system that is relevant to the interpretation of the records, as well as citations for both publications and archived data.
Y1  - 2018
U6  - https://doi.org/10.5194/essd-10-1687-2018
SN  - 1866-3508
SN  - 1866-3516
VL  - 10
IS  - 3
SP  - 1687
EP  - 1713
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Fohlmeister, Jens Bernd
A1  - Plessen, Birgit
A1  - Dudashvili, Alexey Sergeevich
A1  - Tjallingii, Rik
A1  - Wolff, Christian Michael
A1  - Gafurov, Abror
A1  - Cheng, Hai
T1  - Winter precipitation changes during the Medieval Climate Anomaly and the Little Ice Age in arid Central Asia
JF  - Quaternary science reviews : the international multidisciplinary research and review journal
N2  - The strength of the North Atlantic Oscillation (NAO) is considered to be the main driver of climate changes over the European and western Asian continents throughout the last millennium. For example, the predominantly warm Medieval Climate Anomaly (MCA) and the following cold period of the Little Ice Age (LIA) over Europe have been associated with long-lasting phases with a positive and negative NAO index. Its climatic imprint is especially pronounced in European winter seasons. However, little is known about the influence of NAO with respect to its eastern extent over the Eurasian continent. Here we present speleothem records (PC, 8180 and Sr/Ca) from the southern rim of Fergana Basin (Central Asia) revealing annually resolved past climate variations during the last millennium. The age control of the stalagmite relies on radiocarbon dating as large amounts of detrital material inhibit accurate 230Th dating. Present-day calcification of the stalagmite is most effective during spring when the cave atmosphere and elevated water supply by snow melting and high amount of spring precipitation provide optimal conditions. Seasonal precipitation variations cause changes of the stable isotope and Sr/ Ca compositions. The simultaneous changes in these geochemical proxies, however, give also evidence for fractionation processes in the cave. By disentangling both processes, we demonstrate that the amount of winter precipitation during the MCA was generally higher than during the LIA, which is in line with climatic changes linked to the NAO index but opposite to the higher mountain records of Central Asia. Several events of strongly reduced winter precipitation are observed during the LIA in Central Asia. These dry winter events can be related to phases of a strong negative NAO index and all results reveal that winter precipitation over the central Eurasian continent is tightly linked to atmospheric NAO modes by the westerly wind systems. (C) 2017 Elsevier Ltd. All rights reserved.
Y1  - 2017
U6  - https://doi.org/10.1016/j.quascirev.2017.10.026
SN  - 0277-3791
VL  - 178
SP  - 24
EP  - 36
PB  - Elsevier
CY  - Oxford
ER  -