Abrupt weakening of the summer monsoon in northwest India ~4100 yr ago

Climate change has been suggested as a possible cause for the decline of urban centers of the Indus Civilization ∼4000 yr ago, but extant paleoclimatic evidence has been derived from locations well outside the distribution of Indus settlements. Here we report an oxygen isotope record of gastropod aragonite (δ18Oa) from Holocene sediments of paleolake Kotla Dahar (Haryana, India), which is adjacent to Indus settlements and documents Indian summer monsoon (ISM) variability for the past 6.5 k.y. A 4‰ increase in δ18Oa occurred at ca. 4.1 ka marking a peak in the evaporation/precipitation ratio in the lake catchment related to weakening of the ISM. Although dating uncertainty exists in both climate and archaeological records, the drought event 4.1 ka on the northwestern Indian plains is within the radiocarbon age range for the beginning of Indus de-urbanization, suggesting that climate may have played a role in the Indus cultural transformation

Abrupt weakening of the Indian summer monsoon at 8.2 kyr B.P.

An oxygen isotope record of biogenic carbonate from paleolake Riwasa in northwestern (NW) India provides a history of the Indian Summer Monsoon (ISM) from ∼11 to 6 kyr B.P. The lake was dry throughout the Late Glacial period when aeolian sands were deposited. Lacustrine sedimentation commenced in the early Holocene and the lake deepened significantly at ∼9.4 kyr B.P., indicating a strengthening of the ISM in response to summer insolation forcing. This high lake stand was interrupted by an abrupt desiccation, which is marked by a 12-cm limestone hardground that formed during a period of sub-aerial exposure after ∼8.3 kyr B.P. The base of the hardground surface coincides with the beginning of the ‘8.2-kyr B.P. cooling event’ in the North Atlantic that has been associated with a glacial outburst flood and slowdown of Atlantic meridional overturning circulation. The hardground provides robust evidence of a weakening of the ISM on the Indian subcontinent at ∼8.2 kyr B.P., and supports previous results of a strong teleconnection between monsoon Asia and North Atlantic climate. Lacustrine sedimentation resumed at ∼7.9 kyr B.P. suggesting the 8.2-kyr desiccation of paleolake Riwasa represented an abrupt response of the ISM to forcing from the North Atlantic

Adaptation to Variable Environments, Resilience to Climate Change: Investigating Land, Water and Settlement in Indus Northwest India

This paper explores the nature and dynamics of adaptation and resilience in the face of a diverse and varied environmental and ecological context using the case study of South Asia’s Indus Civilization (ca. 3000–1300 BC). Most early complex societies developed in regions where the climatic parameters faced by ancient subsistence farmers were varied but rain falls primarily in one season. In contrast, the Indus Civilization developed in a specific environmental context that spanned a very distinct environmental threshold, where winter and summer rainfall systems overlap. There is now evidence to show that this region was directly subject to climate change during the period when the Indus Civilization was at its height (ca. 2500–1900 BC). The Indus Civilization, therefore, provides a unique opportunity to understand how an ancient society coped with diverse and varied ecologies and change in the fundamental environmental parameters. This paper integrates research carried out as part of the Land, Water and Settlement project in northwest India between 2007 and 2014. Although coming from only one of the regions occupied by Indus populations, these data necessitate the reconsideration of several prevailing views about the Indus Civilization as a whole and invigorate discussion about human-environment interactions and their relationship to processes of cultural transformation

Author Correction: Intensified summer monsoon and the urbanization of Indus Civilization in northwest India.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.NERC (NE/H011463/1

Intensified summer monsoon and the urbanization of Indus Civilization in northwest India

Today the desert margins of northwest India are dry and unable to support large populations, but were densely occupied by the populations of the Indus Civilization during the middle to late Holocene. The hydroclimatic conditions under which Indus urbanization took place, which was marked by a period of expanded settlement into the Thar Desert margins, remains poorly understood. We measured the isotopic values (δ18O and δD) of gypsum hydration water in paleolake Karsandi sediments in northern Rajasthan to infer past changes in lake hydrology, which is sensitive to changing amounts of precipitation and evaporation. Our record reveals that relatively wet conditions prevailed at the northern edge of Rajasthan from ~5.1 ± 0.2 ka BP, during the beginning of the agricultural-based Early Harappan phase of the Indus Civilization. Monsoon rainfall intensified further between 5.0 and 4.4 ka BP, during the period when Indus urban centres developed in the western Thar Desert margin and on the plains of Haryana to its north. Drier conditions set in sometime after 4.4 ka BP, and by ~3.9 ka BP an eastward shift of populations had occurred. Our findings provide evidence that climate change was associated with both the expansion and contraction of Indus urbanism along the desert margin in northwest India

Adaptation to Variable Environments, Resilience to Climate Change: Investigating Land, Water and Settlement in Indus Northwest India

This paper explores the nature and dynamics of adaptation and resilience in the face of a diverse and varied environmental and ecological context using the case study of South Asia’s Indus Civilization (ca. 3000–1300 BC). Most early complex societies developed in regions where the climatic parameters faced by ancient subsistence farmers were varied but rain falls primarily in one season. In contrast, the Indus Civilization developed in a specific environmental context that spanned a very distinct environmental threshold, where winter and summer rainfall systems overlap. There is now evidence to show that this region was directly subject to climate change during the period when the Indus Civilization was at its height (ca. 2500–1900 BC). The Indus Civilization, therefore, provides a unique opportunity to understand how an ancient society coped with diverse and varied ecologies and change in the fundamental environmental parameters. This paper integrates research carried out as part of the Land, Water and Settlement project in northwest India between 2007 and 2014. Although coming from only one of the regions occupied by Indus populations, these data necessitate the reconsideration of several prevailing views about the Indus Civilization as a whole and invigorate discussion about human-environment interactions and their relationship to processes of cultural transformation

Adaptation to Variable Environments, Resilience to Climate Change: Investigating Land, Water and Settlement in Indus Northwest India

This paper explores the nature and dynamics of adaptation and resilience in the face of a diverse and varied environmental and ecological context using the case study of South Asia’s Indus Civilization (ca. 3000–1300 BC). Most early complex societies developed in regions where the climatic parameters faced by ancient subsistence farmers were varied but rain falls primarily in one season. In contrast, the Indus Civilization developed in a specific environmental context that spanned a very distinct environmental threshold, where winter and summer rainfall systems overlap. There is now evidence to show that this region was directly subject to climate change during the period when the Indus Civilization was at its height (ca. 2500–1900 BC). The Indus Civilization, therefore, provides a unique opportunity to understand how an ancient society coped with diverse and varied ecologies and change in the fundamental environmental parameters. This paper integrates research carried out as part of the Land, Water and Settlement project in northwest India between 2007 and 2014. Although coming from only one of the regions occupied by Indus populations, these data necessitate the reconsideration of several prevailing views about the Indus Civilization as a whole and invigorate discussion about human-environment interactions and their relationship to processes of cultural transformation

Living in the hinterland: Survey and excavations at Lohari Ragho 2015–2017

Living in the hinterland: Survey and excavations at Lohari Ragho 2015–201

Regional character of the “global monsoon”: paleoclimate insights from Northwest Indian lacustrine sediments

The concept of a “global monsoon” proposes that the annual insolation cycle and global-scale atmospheric circulation drive and synchronize regional mon-soons. However, model, proxy, and observational studies reveal differences in the regional variability of the summer monsoon and its direct response to solar forcing and glacial boundary conditions. Here, we focus on paleoenvironmental data derived from paleolake sediments in northwest India. These paleolakes straddle a precipitation gra-dient from sub-humid to semi-arid to arid plains and contain a wealth of information about summer monsoon variability at regional scale over the past 10,000 years. The paleolake records provide compelling evidence of significant regional differences in the timing of monsoon responses to orbital forcings; only sub-humid to semi-arid lakes resemble monsoon reconstructions from marine sediment and speleothem archives, while the arid region lakes contain regional hydroclimate histories. Extracting regional trends from the global signature of monsoon variability is necessary for understand-ing the regional impact of future climate warming on the monsoon system and human populations. The paleolakes in northwest India highlight the importance of con-sidering the specific location of archive and signal heterogeneity when interpret-ing monsoon records. Results indicate that detailed records are required from other monsoon regions to improve knowledge of the imprints of the complex monsoon system at regional scales.Published versio