Conference PaperPDF Available

EVIDENCES OF ROMAN WARM PERIOD AND DARK AGES OF COLD PERIOD FROM THE ACTIVE MUDFLATS OF THE WESTERN INDIAN COAST: MAJOR CLIMATIC EVENT OF FIRST MILLENNIUM

Authors:
Upasana Swaroop Banerji at Ministry of Earth Sciences
Upasana Swaroop Banerji
Ravi Bhushan at Physical Research Laboratory
Ravi Bhushan
A.J. Timothy Jull at The University of Arizona
A.J. Timothy Jull
Download full-text PDF
Read full-text
Download citation

Abstract

The last two millennia have been an critical period to document climate perturbation for the evaluation of anthropogenic interferences and prediction of future climate changes. Increased availability of proxy data set has helped in better understanding of climatic events especially Medieval warm period (MWP) and Little Ice age (LIA) (Lamb, 1965), its amplitude, synchroneity and spatial extent for the last millennium. The first millennium known for Roman Warm Period (RWP) and Dark Ages of Cold period (DACP) is yet to be explored in context of the Indian subcontinent. Solar cycle plays a significant role in controlling the Indian summer monsoon (ISM) and is responsible for more than 80% of rainfall over Indian subcontinent. RWP and DACP are two known events resulted due to solar millennial scale cycles (Abreu et al., 2010). The paucity in records for the occurrence of RWP and DACP from the Indian subcontinent is a major impediment which encouraged us to study the paleomonsoonal variations resulted in climate anomaly of first millennium. Diu Island in the northwestern Indian coast mainly receives rainfall during ISM. Diu Island comprises extensive mudflats which gets inundated during high tides and exposed during low tides thus it archives climate change during its depositional process. A sediment core retrieved from the active mudflats of Diu Island was investigated for various geochemical parameters to decipher paleomonsoonal variation during the first millennium. The chronology of the sediment core was estimated by both AMS 14 C and 210 Pb dating technique supported by 137 Cs. The study area though deprived of perennial river has ephemeral rivers which gets activated during ISM and contributes terrigenous flux to the region. These detrital proxy suggest change in the hydrological conditions persisted in the region as a function of ISM variation. Enhanced major and trace elements suggest improved ISM with warm and humid conditions between 20101500 cal yr BP, corroborating well with RWP. Low elemental concentration between 15001050 cal yr BP suggest weakening of ISM resulting in arid climate corresponds to DACP. Spectral analysis of time series data show ~450, 333, 250 and 130 yr solar periodicities indicating the solar forcing of ISM. RWP and DACP climate events have been identified to be affected by Eddy solar cycle (~500 yr). The present study demonstrates first record of DACP event from the Indian subcontinent. References Abreu, J. A., Beer, J., & Ferriz-Mas, A. (2010, June). Past and future solar activity from cosmogenic radionuclides. In SOHO-23: understanding a peculiar solar minimum (Vol. 428, p. 287). Lamb, Hubert Horace. "The early medieval warm epoch and its sequel." Palaeogeography, Palaeoclimatology, Palaeoecology 1 (1965): 13-37.
Content uploaded by Upasana Swaroop Banerji
Author content
All content in this area was uploaded by Upasana Swaroop Banerji on Sep 06, 2017
Content may be subject to copyright.
5th National Conference of Ocean Society of India
OSICON-17
August 28-30, 2017
ESSO-National Centre for Earth Science Studies, Thiruvananthapuram
1
EVIDENCES OF ROMAN WARM PERIOD AND DARK AGES OF COLD PERIOD
FROM THE ACTIVE MUDFLATS OF THE WESTERN INDIAN COAST: MAJOR
CLIMATIC EVENT OF FIRST MILLENNIUM
Upasana S. Banerji*1, Ravi Bhushan1 and A.J.T. Jull2
1Geosciences Division, Physical Research Laboratory, Ahmedabad-380 009, Gujarat, India
2 NSF Arizona AMS Laboratory, University of Arizona, Tucson, AZ 85721, USA
Email: upasanabanerji@gmail.com*
The last two millennia have been an critical period to document climate perturbation for the
evaluation of anthropogenic interferences and prediction of future climate changes.
Increased availability of proxy data set has helped in better understanding of climatic events
especially Medieval warm period (MWP) and Little Ice age (LIA) (Lamb, 1965), its amplitude,
synchroneity and spatial extent for the last millennium. The first millennium known for Roman
Warm Period (RWP) and Dark Ages of Cold period (DACP) is yet to be explored in context of
the Indian subcontinent. Solar cycle plays a significant role in controlling the Indian summer
monsoon (ISM) and is responsible for more than 80% of rainfall over Indian subcontinent.
RWP and DACP are two known events resulted due to solar millennial scale cycles (Abreu et
al., 2010). The paucity in records for the occurrence of RWP and DACP from the Indian
subcontinent is a major impediment which encouraged us to study the paleomonsoonal
variations resulted in climate anomaly of first millennium.
Diu Island in the north-western Indian coast mainly receives rainfall during ISM. Diu Island
comprises extensive mudflats which gets inundated during high tides and exposed during low
tides thus it archives climate change during its depositional process. A sediment core
retrieved from the active mudflats of Diu Island was investigated for various geochemical
parameters to decipher paleomonsoonal variation during the first millennium. The
chronology of the sediment core was estimated by both AMS 14C and 210Pb dating technique
supported by 137Cs.
The study area though deprived of perennial river has ephemeral rivers which gets activated
during ISM and contributes terrigenous flux to the region. These detrital proxy suggest change
in the hydrological conditions persisted in the region as a function of ISM variation. Enhanced
major and trace elements suggest improved ISM with warm and humid conditions between
20101500 cal yr BP, corroborating well with RWP. Low elemental concentration between
15001050 cal yr BP suggest weakening of ISM resulting in arid climate corresponds to DACP.
Spectral analysis of time series data show ~450, 333, 250 and 130 yr solar periodicities
indicating the solar forcing of ISM. RWP and DACP climate events have been identified to be
affected by Eddy solar cycle (~500 yr). The present study demonstrates first record of DACP
event from the Indian subcontinent.
References
Abreu, J. A., Beer, J., & Ferriz-Mas, A. (2010, June). Past and future solar activity from
cosmogenic radionuclides. In SOHO-23: understanding a peculiar solar minimum (Vol. 428, p.
287).
Lamb, Hubert Horace. "The early medieval warm epoch and its sequel." Palaeogeography,
Palaeoclimatology, Palaeoecology 1 (1965): 13-37.
ResearchGate has not been able to resolve any citations for this publication.
Past and Future Solar Activity from Cosmogenic Radionuclides
Article
  • Jun 2010
The sunspot record since 1610 shows cycles of magnetic activity with an irregular distribution of amplitudes and with a period around 11 years. They are modulated on longer timescales and were interrupted by the Maunder minimum in the 17th century. During the past several cycles the average solar activity was very high. This raises the question whether the present grand maximum is likely to terminate soon or even to be followed by another (Maunder-like) grand minimum. Cosmogenic radionuclides stored in natural archives such as 10Be in ice cores and 14C in tree rings have proven to be a valuable tool in reconstructing past solar activity and changes in the geomagnetic field intensity over several millennia. At present, this is the only method to extend back the record of solar activity beyond the instrumental period. The main properties of solar activity will be discussed for the past 10,000 years. A detailed statistical analysis of this record allows us to derive the life expectancy of the present grand maximum, which will come soon to an end. By using the same approach applied to the intervals between grand minima, we expect a grand minimum in solar activity to occur within the next 100 years.
View
The Early Medieval Warm Epoch and its sequel
Article
  • Jan 1965
  • PALAEOGEOGR PALAEOCL
Evidence has been accumulating in many fields of investigation pointing to a notably warm climate in many parts of the world, that lasted a few centuries around A.D. 1000–1200, and was followed by a decline of temperature levels till between 1500 and 1700 the coldest phase since the last ice age occurred. There has been some controversy as to whether this climatic variation was geeat enough to be significant in connection with the balance of Nature or the economy of Man. It is time to marshal the evidence and attempt a numerical assessment of the climatic values involved in some area for which there are enough data to permit it. This is attempted here and provides an illustration of how data from the realms of botany, historical document research and meteorology may be used to confirm, correct and amplify each other.Changes of prevailing temperature and rainfall in England between periods of 50–150 years duration around 1200 and around 1600 are found which, on all the evidence at present available, probably amounted to 1.2–1.4°C and 10% respectively. Changes in some reasons of the year may have exceeded these ranges of the annual mean. The changes indicated are small enough to account for earlier impressions in some quarters that there has been no significant change of climate in the last 2,500 years, yet they are big enough to be surprising in terms of previous meteorological knowledge and undoubtedly upsetting for the human economies of those times (and perhaps of any time).It is by quantitative assessment of climatic values for epochs, such as the one here treated, for which some sort of extreme character is indicated by reliably dated evidence, that palaeoclimatology may hope to progress. The time-scale of the epoch here studied appears similar to that of several earluer climatic oscillations of known importance to the history of the European fauna and flora, which for obvious reasons cannot be submitted to equally close meteorological analysis. It is essential that the geographical distribution of climatic values arrived at, should be examined (as is done here) for consistency and the possibility of a reasonable interpretation in terms of the condition of the wind and ocean circulations.
View