TY  - THES
A1  - Ambili, Anoop
T1  - Lake sediments as climate and tectonic archives in the Indian summer monsoon domain
T1  - Seesedimente als Klima- und Tektonikarchive im Einflussbereich des Indischen Sommermonsuns
N2  - The Indian summer monsoon (ISM) is one of the largest climate systems on earth and impacts the livelihood of nearly 40% of the world’s population. Despite dedicated efforts, a comprehensive picture of monsoon variability has proved elusive largely due to the absence of long term high resolution records, spatial inhomogeneity of the monsoon precipitation, and the complex forcing mechanisms (solar insolation, internal teleconnections for e.g., El Niño-Southern Oscillation, tropical-midlatitude interactions). My work aims to improve the understanding of monsoon variability through generation of long term high resolution palaeoclimate data from climatically sensitive regions in the ISM and westerlies domain. To achieve this aim I have (i) identified proxies (sedimentological, geochemical, isotopic, and mineralogical) that are sensitive to environmental changes; (ii) used the identified proxies to generate long term palaeoclimate data from two climatically sensitive regions, one in NW Himalayas (transitional westerlies and ISM domain in the Spiti valley and one in the core monsoon zone (Lonar lake) in central India); (iii) undertaken a regional overview to generate “snapshots” of selected time slices; and (iv) interpreted the spatial precipitation anomalies in terms of those caused by modern teleconnections. This approach must be considered only as the first step towards identifying the past teleconnections as the boundary conditions in the past were significantly different from today and would have impacted the precipitation anomalies. As the Spiti valley is located in the in the active tectonic orogen of Himalayas, it was essential to understand the role of regional tectonics to make valid interpretations of catchment erosion and detrital influx into the lake. My approach of using integrated structural/morphometric and geomorphic signatures provided clear evidence for active tectonics in this area and demonstrated the suitability of these lacustrine sediments as palaleoseismic archives. The investigations on the lacustrine outcrops in Spiti valley also provided information on changes in seasonality of precipitation and occurrence of frequent and intense periods (ca. 6.8-6.1 cal ka BP) of detrital influx indicating extreme hydrological events in the past. Regional comparison for this time slice indicates a possible extended “break-monsoon like” mode for the monsoon that favors enhanced precipitation over the Tibetan plateau, Himalayas and their foothills. My studies on surface sediments from Lonar lake helped to identify environmentally sensitive proxies which could also be used to interpret palaeodata obtained from a ca. 10m long core raised from the lake in 2008. The core encompasses the entire Holocene and is the first well dated (by 14C) archive from the core monsoon zone of central India. My identification of authigenic evaporite gaylussite crystals within the core sediments provided evidence of exceptionally drier conditions during 4.7-3.9 and 2.0-0.5 cal ka BP. Additionally, isotopic investigations on these crystals provided information on eutrophication, stratification, and carbon cycling processes in the lake.
N2  - Der Indische Sommer Monsun (ISM) ist eines der bedeutendsten Klimaphänomene auf der Erde und hat großen Einfluss auf die Lebensbedingungen und -grundlagen von nahezu 40% der Weltbevölkerung. Trotz großer Bemühungen ist es bisher nicht gelungen ein genaues und umfassendes Verständnis der Monsun-Variabilität zu gewinnen. Hauptgründe dafür sind das Fehlen von langjährigen und hochaufgelösten Klimazeitreihen, räumlichen Inhomogenitäten in den Niederschlagsverteilungen und die Komplexität der treibenden klimatischen Mechanismen (Sonneneinstrahlung, interne Wechselwirkungen des Klimasystems, wie z.B. zwischen Tropen und mittleren Breiten oder die Auswirkungen der El Niño Oszillation). Die Zielsetzung der hier vorgestellten Arbeit ist ein verbessertes Verständnis der Monsun-Variabilität zu entwickeln, auf Basis von hochaufgelösten und weit reichenden Paläoklimazeitreihen aus klimasensitiven Regionen des ISM und der Westwindzone. Um die Zielsetzung umzusetzen habe ich: (i) Proxys identifiziert (sedimentologische, geochemische, isotopische, und mineralogische), die empfindlich auf Umweltveränderungen reagieren; (ii) die identifizierten Proxys zur Erzeugung von langjährigen Paläoklima-Daten für zwei klimasensible Regionen verwendet, eine im NW des Himalaja (Übergangs-Westwindzone und ISM Gebiet von Spity Valley) und eine in der Kernzone des Monsun (Lonar-See) in Zentralindien; (iii) Übersichts-"Momentaufnahmen" der regionalen klimatischen Bedingungen für ausgewählte Zeitpunkte der Vergangenheit erzeugt; und (iv) räumliche Niederschlagsanomalien in Hinblick auf heutige Wechselbeziehungen im Klimasystem interpretiert. Dieser Ansatz stellt allerdings nur einen ersten Schritt zur Identifizierung von paläoklimatischen Wechselbeziehungen im Monsunsystem dar, da sich die Randbedingungen in der Vergangenheit deutlich von den heutigen unterscheiden und diese einen signifikanten Einfluss auf die Niederschlagsanomalien haben. Da das Spity Valley im tektonisch aktiven Himalaja-Orogen lokalisiert ist, ist es von entscheidender Bedeutung die regionalen tektonischen Prozesse zu verstehen, um Erosionsvorgänge des Einzugsgebiets und die Einfuhr von Detritus in den See korrekt interpretieren zu können. Mein Ansatz der Nutzung kombinierter strukturell/morphometrischer und geomorphologischer Charakteristiken lieferte klare Beweise für aktive Tektonik im untersuchten Gebiet und demonstrierte damit die Eignung dieser lakustrinen Sedimente als paläoseismisches Archiv. Die Untersuchung lakustriner Aufschlüsse in Spity Valley lieferte auch Informationen saisonale Änderung der Niederschlagsverteilung sowie das Auftreten von häufigen und intensiven Perioden (ca. 6,8-6,1 cal ka BP) detritischer Einfuhr, welche auf extreme hydrologische Ereignisse in der Vergangenheit schließen lässt. Ein regionaler Vergleich dieser Periode deutet auf einen möglicherweise erweiterten „break-monsoon-like“ Modus für den Monsun hin, welcher hohe Niederschläge über dem Tibetischen Plateau, dem Himalaja und seinen Gebirgsausläufern begünstigt. Meine Studien an den Oberflächensedimenten des Lonar-Sees haben dazu beigetragen umweltsensitive Proxys zu identifizieren, die auch zur Interpretation von Paläodaten von einem ca. 10 m langen Sedimentkern genutzt wurden, der 2008 erbohrt wurde. Der Kern umfasst das gesamte Holozän und stellt das erste gut 14C-datierte Archiv aus der Kernmonsunzone Zentralindiens dar. Die Identifizierung von authigenen Evaporit-Kristallen (Gaylussite) innerhalb der Sedimente liefert einen Beweis für ungewöhnlich trockene Bedingungen in den Perioden zwischen 4,7-3,9 und 2,0-0,5 cal ka BP. Darüber hinaus lieferten Isotopen-Untersuchungen dieser Kristalle Informationen zur Eutrophierung, Stratifikation und zum Kohlenstoff-Kreislauf des Sees.
KW  - Gaylussite
KW  - Indische Sommer Monsun
KW  - Seesediment
KW  - Spity Valley
KW  - Lonarsee
KW  - Gaylussite
KW  - Indian summer monsoon
KW  - Lake sediments
KW  - Spiti valley
KW  - Lonar lake
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-64799
ER  - 
TY  - JOUR
A1  - Malik, Nishant
A1  - Bookhagen, Bodo
A1  - Marwan, Norbert
A1  - Kurths, Jürgen
T1  - Analysis of spatial and temporal extreme monsoonal rainfall over South Asia using complex networks
JF  - Climate dynamics : observational, theoretical and computational research on the climate system
N2  - We present a detailed analysis of summer monsoon rainfall over the Indian peninsular using nonlinear spatial correlations. This analysis is carried out employing the tools of complex networks and a measure of nonlinear correlation for point processes such as rainfall, called event synchronization. This study provides valuable insights into the spatial organization, scales, and structure of the 90th and 94th percentile rainfall events during the Indian summer monsoon (June-September). We furthermore analyse the influence of different critical synoptic atmospheric systems and the impact of the steep Himalayan topography on rainfall patterns. The presented method not only helps us in visualising the structure of the extreme-event rainfall fields, but also identifies the water vapor pathways and decadal-scale moisture sinks over the region. Furthermore a simple scheme based on complex networks is presented to decipher the spatial intricacies and temporal evolution of monsoonal rainfall patterns over the last 6 decades.
KW  - Indian summer monsoon
KW  - Event synchronization
KW  - Complex networks
KW  - Rainfall patterns
Y1  - 2012
U6  - https://doi.org/10.1007/s00382-011-1156-4
SN  - 0930-7575
VL  - 39
IS  - 3-4
SP  - 971
EP  - 987
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Prasad, Sushma
A1  - Anoop, A.
A1  - Riedel, N.
A1  - Sarkar, Saswati
A1  - Menzel, P.
A1  - Basavaiah, Nathani
A1  - Krishnan, R.
A1  - Fuller, D.
A1  - Plessen, Birgit
A1  - Gaye, B.
A1  - Roehl, U.
A1  - Wilkes, H.
A1  - Sachse, Dirk
A1  - Sawant, R.
A1  - Wiesner, M. G.
A1  - Stebich, M.
T1  - Prolonged monsoon droughts and links to Indo-Pacific warm pool: A Holocene record from Lonar Lake, central India
JF  - Earth & planetary science letters
N2  - Concerns about the regional impact of global climate change in a warming scenario have highlighted the gaps in our understanding of the Indian Summer Monsoon (ISM, also referred to as the Indian Ocean summer monsoon) and the absence of long term palaeoclimate data from the central Indian core monsoon zone (CMZ). Here we present the first high resolution, well-dated, multiproxy reconstruction of Holocene palaeoclimate from a 10 m long sediment core raised from the Lonar Lake in central India. We show that while the early Holocene onset of-intensified monsoon in the CMZ is similar to that reported from other ISM records, the Lonar data shows two prolonged droughts (PD, multidecadal to centennial periods of weaker monsoon) between 4.6-3.9 and 2-0.6 cal ka. A comparison of our record with available data from other ISM influenced sites shows that the impact of these PD was observed in varying degrees throughout the ISM realm and coincides with intervals of higher solar irradiance. We demonstrate that (i) the regional warming in the Indo-Pacific Warm Pool (IPWP) plays an important role in causing ISM PD through changes in meridional overturning circulation and position of the anomalous Walker cell; (ii) the long term influence of conditions like El Nino-Southern Oscillation (ENSO) on the ISM began only ca. 2 cal ka BP and is coincident with the warming of the southern IPWP; (iii) the first settlements in central India coincided with the onset of the first PD and agricultural populations flourished between the two PD, highlighting the significance of natural climate variability and PD as major environmental factors affecting human settlements.
KW  - Indian summer monsoon
KW  - ENSO
KW  - prolonged droughts
KW  - Holocene
KW  - Lonar Lake
Y1  - 2014
U6  - https://doi.org/10.1016/j.epsl.2014.01.043
SN  - 0012-821X
SN  - 1385-013X
VL  - 391
SP  - 171
EP  - 182
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Mishra, Praveen Kumar
A1  - Prasad, Sushma
A1  - Anoop, A.
A1  - Plessen, Birgit
A1  - Jehangir, Arshid
A1  - Gaye, Birgit
A1  - Menzel, Philip
A1  - Weise, Stephan M.
A1  - Yousuf, Abdul R.
T1  - Carbonate isotopes from high altitude Tso Moriri Lake (NW Himalayas) provide clues to late glacial and Holocene moisture source and atmospheric circulation changes
JF  - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences
N2  - High resolution isotopic (delta O-18 and delta C-13) investigations on endogenic carbonates (calcite/aragonite) from Tso Moriri Lake, NW Himalaya show dramatic fluctuations during the late glacial and the early Holocene, and a persistent enrichment trend during the late Holocene. Changes in this lake are largely governed by the [input (meltwater + monsoon precipitation)/evaporationj (WE) ratio, also reflected in changes in the carbonate mineralogy with aragonite being formed during periods of lowest I/E. Using new isotopic data on endogenic carbonates in combination with the available data on geochemistry, mineralogy, and reconstructed mean annual precipitation, we demonstrate that the late glacial and early Holocene carbonate delta O-18 variability resulted from fluctuating Indian summer monsoon (ISM) precipitation in NW Himalaya. This region experienced increasing ISM precipitation between ca. 13.1 and 11.7 cal ka and highest ISM precipitation during the early Holocene (11.2-8.5 cal ka). However, during the late Holocene, evaporation was the dominant control on the carbonate delta O-18. Regional comparison of reconstructed hydrological changes from Tso Moriri Lake with other archives from the Asian summer monsoon and westerlies domain shows that the intensified westerly influence that resulted in higher lake levels (after 8 cal ka) in central Asia was not strongly felt in NW Himalaya. (C) 2015 Elsevier B.V. All rights reserved.
KW  - Carbonates
KW  - Holocene
KW  - Indian summer monsoon
KW  - Isotopes
KW  - Tso Moriri Lake
Y1  - 2015
U6  - https://doi.org/10.1016/j.palaeo.2015.02.031
SN  - 0031-0182
SN  - 1872-616X
VL  - 425
SP  - 76
EP  - 83
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Mishra, Praveen Kumar
A1  - Anoop, Ambili
A1  - Schettler, Georg
A1  - Prasad, Sushma
A1  - Jehangir, Arshid
A1  - Menzel, Peter
A1  - Naumann, Rudolf
A1  - Yousuf, A. R.
A1  - Basavaiah, Nathani
A1  - Deenadayalan, Kannan
A1  - Wiesner, Martin G.
A1  - Gaye, Birgit
T1  - Reconstructed late Quaternary hydrological changes from Lake Tso Moriri, NW Himalaya
JF  - Quaternary international : the journal of the International Union for Quaternary Research
N2  - We present the results of our investigations on the radiocarbon dated core sediments from the Lake Tso Moriri, NW Himalaya aimed at reconstructing palaeohydrological changes in this climatically sensitive region. Based on the detailed geochemical, mineralogical and sedimentological analysis, we recognise several short-term fluctuations superimposed upon seven major palaeohydrological stages identified in this lake since similar to 26 cal ka. Stage I (>20.2 cal ka): shallow lake characterised by input of coarse-grained detrital sediments; Stage II (20.2-16.4 cal ka): lake deepening and intensification of this trend ca. 18 cal ka; Stage III (16.4-11.2 cal ka): rising lake levels with a short term wet phase (13.1-11.7 cal ka); Stage IV (11.2-8.5 cal ka): early Holocene hydrological maxima and highest lake levels inferred to have resulted from early Holocene Indian monsoon intensification, as records from central Asia indicate weaker westerlies during this interval; Stage V (8.5-5.5 cal ka): mid-Holocene climate deterioration; Stage VI (5.5-2.7 cal ka): progressive lowering of lake level; Stage VII (2.7-0 cal ka): onset of modern conditions. The reconstructed hydrological variability in Lake Tso Moriri is governed by temperature changes (meltwater inflow) and monsoon precipitation (increased runoff). A regional comparison shows considerable differences with other palaeorecords from peninsular India during late Holocene. (C) 2014 Elsevier Ltd and INQUA. All rights reserved.
KW  - Authigenic carbonates
KW  - Holocene
KW  - Indian summer monsoon
KW  - Lake sediments
KW  - Tso Moriri Lake
KW  - Westerlies
Y1  - 2015
U6  - https://doi.org/10.1016/j.quaint.2014.11.040
SN  - 1040-6182
SN  - 1873-4553
VL  - 371
SP  - 76
EP  - 86
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Mishra, Praveen Kumar
A1  - Prasad, Sushma
A1  - Marwan, Norbert
A1  - Anoop, A.
A1  - Krishnan, R.
A1  - Gaye, Birgit
A1  - Basavaiah, N.
A1  - Stebich, Martina
A1  - Menzel, Philip
A1  - Riedel, Nils
T1  - Contrasting pattern of hydrological changes during the past two millennia from central and northern India
BT  - regional climate difference or anthropogenic impact?
JF  - Global and planetary change
N2  - High resolution reconstructions of the India Summer Monsoon (ISM) are essential to identify regionally different patterns of climate change and refine predictive models. We find opposing trends of hydrological proxies between northern (Sahiya cave stalagmite) and central India (Lonar Lake) between 100 and 1300 CE with the strongest anti-correlation between 810 and 1300 CE. The apparently contradictory data raise the question if these are related to widely different regional precipitation patterns or reflect human influence in/around the Lonar Lake. By comparing multiproxy data with historical records, we demonstrate that only the organic proxies in the Lonar Lake show evidence of anthropogenic impact. However, evaporite data (mineralogy and delta O-18) are indicative of precipitation/evaporation (P/E) into the Lonar Lake. Back-trajectories of air-mass circulation over northern and central India show that the relative contribution of the Bay of Bengal (BoB) branch of the ISM is crucial for determining the delta O-18 of carbonate proxies only in north India, whereas central India is affected significantly by the Arabian Sea (AS) branch of the ISM. We conclude that the delta O-18 of evaporative carbonates in the Lonar Lake reflects P/E and, in the interval under consideration, is not influenced by source water changes. The opposing trend between central and northern India can be explained by (i) persistent multidecadal droughts over central India between 810 and 1300 CE that provided an effective mechanism for strengthening sub-tropical westerly winds resulting in enhancement of wintertime (non-monsoonal) rainfall over northern parts of the Indian subcontinent, and/or (ii) increased moisture influx to northern India from the depleted BoB source waters.
KW  - ENSO
KW  - Isotopes
KW  - Indian summer monsoon
KW  - Lonar Lake
KW  - Stalagmites
KW  - Westerlies
Y1  - 2017
U6  - https://doi.org/10.1016/j.gloplacha.2017.12.005
SN  - 0921-8181
SN  - 1872-6364
VL  - 161
SP  - 97
EP  - 107
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Köhn-Reich, Lisei
A1  - Bürger, Gerd
T1  - Dynamical prediction of Indian monsoon
BT  - past and present skill
JF  - International Journal of Climatology
N2  - Ongoing development of dynamical atmosphere-ocean general circulation models keep expectations high regarding seasonal predictions of Indian monsoon rainfall. This study compares past and present skill of four currently operating forecasting systems, CFSv2 from NCEP, ENSEMBLES, System 4 and the newest SEAS5 from ECMWF, by analysing correlations of respective hindcasts with observed all-India summer rainfall. For the common time period 1982-2005, only ENSEMBLES and CFSv2 give significantly skilful forecasts. It is shown that skill is highly dependent on the chosen time period. Especially the intense El Nino of 1997 seems to degrade the predictions, most notably for SEAS4 and SEAS5 which seem to be linked to El Nino too strongly. We show that by discarding that year, a regime shift in the 1990s is no longer visible. Overall, we observe a convergence of skill towards the present with correlations of about 0.4 for CFSv2 and of 0.6 for System 4 and SEAS5.
KW  - correlation skill
KW  - dynamical seasonal prediction
KW  - Indian summer monsoon
Y1  - 2019
U6  - https://doi.org/10.1002/joc.6039
SN  - 0899-8418
SN  - 1097-0088
VL  - 39
IS  - 8
SP  - 3574
EP  - 3581
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Regmi, Shakil
A1  - Bookhagen, Bodo
T1  - The spatial pattern of extreme precipitation from 40 years of gauge data in the central Himalaya
JF  - Weather and climate extremes
N2  - The topography of the Himalaya exerts a substantial control on the spatial distribution of monsoonal rainfall, which is a vital water source for the regional economy and population. But the occurrence of short-lived and high-intensity precipitation results in socio-economic losses. This study relies on 40 years of daily data from 204 ground stations in Nepal to derive extreme precipitation thresholds, amounts, and days at the 95th percentile. We additionally determine the precipitation magnitude-frequency relation. We observe that extreme precipitation amounts follow an almost uniform band parallel to topographic contour lines in the southern Himalaya mountains in central and eastern Nepal but not in western Nepal. The relationship of extreme precipitation indices with topographic relief shows that extreme precipitation thresholds decrease with increasing elevation, but extreme precipitation days increase in higher elevation areas. Furthermore, stations above 1 km elevation exhibit a power-law relation in the rainfall magnitude-frequency framework. Stations at higher elevations generally have lower values of power-law exponents than low elevation areas. This suggests a fundamentally different behaviour of the rainfall distribution and an increased occurrence of extreme rainfall storms in the high elevation areas of Nepal.
KW  - Himalaya
KW  - Nepal
KW  - Indian summer monsoon
KW  - Precipitation
KW  - Extreme
KW  - precipitation
Y1  - 2022
U6  - https://doi.org/10.1016/j.wace.2022.100470
SN  - 2212-0947
VL  - 37
PB  - Elsevier
CY  - Amsterdam
ER  -