Context
· Secrets hidden in
ancient lake sediment deposits recovered from the Indus River valley in Ladakh
have helped retrace the climate since last deglaciation from 19.6 to 6.1
thousand years, paving the path towards understanding climate variation during
the era.
Importance of
Ladakh region:
· Ladakh region in the Trans-Himalaya forms an
environmental boundary between North Atlantic and monsoon forcings. Its location is ideal to gain insight into the
variations of the atmospheric circulations like westerly and Indian summer
monsoon.
· Plethora of
sedimentary archives exist in the region that can be used to extract past
climate information. Among them, the sediment
deposits in lakes, due to their continuous sedimentation rate, are useful
in attesting both short and long-term climatic changes. Therefore many studies
from the Ladakh region have been attempted from lacustrine sequences to provide information about climate change.
However, most of these studies are focused only in the Holocene period (around
last 10 thousand years), and older periods are less addressed.
· Large-scale climate
reorganization occurs during the shift from glacial to interglacial climate. In
particular, mountain regions are more
vulnerable to these changes owing to their geomorphological set-up.
Therefore it is pertinent to have a clear and better understanding of how the
hydroclimate of a region is changing as climate shifts from an overall colder
to an overall warmer condition.
Research method:
· Noticing the presence
of numerous ancient lake deposits all along the Indus River that were easy to
identify, continuous, and accessible, Scientists from BirbalSahni Institute of Palaeosciences (BSIP), an autonomous institute
of Department of Science and Technology, sampled sediments from 18 m thick
sediment sequence at an altitude of 3287 m and carried out meticulous
laboratory analysis of the samples.
· They used physical characteristics like colour
texture, grain size, grain composition, total organic carbon, and magnetic
parameters of sediments to extract past climate information from the palaeolake
sedimentary archive. This was used to reconstruct
palaeoclimate variations of the period.
Findings of the Research:
· The researchers found
that cold arid climate influenced by westerly circulation reigned for the last
19.6 to 11.1 ka (thousand years). Thereafter from 11.1 to 7.5 ka, monsoon
forcings dominated the climate of the region, following which the orbitally
controlled solar insolation took over, influencing
the position of Inter Tropical Convergence Zone ITCZ and was the key driver
of the variability of these atmospheric circulations. A short wet phase from
around 17.4 to 16.5 ka within the dominant westerly period is attributed to the
early wet phase of a two-fold H1 event called. Westerlies regained strength
from 7.5 to 6.1 ka during the mid-Holocene, coinciding with decreasing
insolation, weakening monsoon, and enhanced
El Nino activities.
· The study published
in the journal PALAEO3 can help gain insights into the past climate variations
since the last deglaciation that followed the Last Glacial Maxima and recognize
the influence of different forcing mechanisms and teleconnections to improve
the understanding of climate variability during the dynamic transitional phase
as well as the evolution of ISM and Westerlies in the transition phase during
the deglaciation time period.
