Fingerprint of volcanic forcing on the ENSO–Indian monsoon coupling

<p>The coupling between the El Niño–Southern Oscillation (ENSO) and Indian Monsoon (IM) plays a significant role in the summer rainfall over the Indian subcontinent. In this study, we provide insights into the IM variability with regard to the degree of ENSO variability and radiative forcing from large volcanic eruptions (LVEs). Volcanic dust and gas injected into the stratosphere during major eruptions influence the ENSO from seasonal to interannual timescales. However, the effects of LVEs on the ENSO-IM coupling remain unclear. The relationship between ENSO and IM systems in the context of LVEs is examined using a panoply of datasets and advanced statistical analysis techniques in this study. We find that there is a significant enhancement of the phase-synchronization between ENSO and IM oscillations due to increase in angular frequency of ENSO in the last millennium. Twin surrogates-based statistical significance testing is also used to affirm this result and similar evidence is found in the combinations of 14 ENSO and 11 IM paleoclimate proxy records in the last millennium. Bayesian probabilities conditioned with and without LVEs show LVEs lead to a strong ENSO-IM phase-coupling, with the probabilities remaining higher till the fourth year from the eruption. A large-ensemble climate model experiment with and without the 1883 Krakatoa eruption is conducted using the IITM-ESM, and also with varied volcanic radiative forcing (VRF) depending on the evolved state of ENSO. The simulations show that LVEs force the ENSO-IM systems into a coupled state, and increase (decrease) in the VRF leads to an enhanced (decreased) probability of the phase synchronisation of ENSO-IM systems with a high chance of El Niño-IM drought in the year following the LVE. Our results promisingly pave a way not only for improving the seasonal monsoon prediction improvements but also for the regional impact assessment from the proposed geo-engineering activities over the South Asian region.</p>

Climate variability following large volcanic eruption: CMIP6 model investigation

<p>Volcanic eruptions are an important driver of climate variability. Multiple literature sources have shown that after large explosive eruptions there is a decrease in global mean temperature, caused by an increased amount of stratospheric aerosols which influence the global radiative budget. In this study, we investigate the changes in several climate variables after a volcanic eruption. Using ESMValTool (Earth System Model Evaluation Tool) on an ensemble of historical simulations from CMIP6, such variables as global mean surface temperature (GMST), Arctic sea ice area and Nino 3.4 index were analyzed following the 1883 Krakatoa eruption. While there is a definite decrease in the multi-model mean GMST after the eruption, other indices do not show as prominent change. The reasons for this behavior are under investigation. </p>

“The wrathful sunset glared…”: The Krakatoa Sunsets in Victorian Science and Art

The eruption of Krakatoa on August 27, 1883 was an event both tragic and spectacular. Thousands of lives were lost; sea waves and atmospheric disturbances were detected around the globe. Billions of tons of volcanic ash were thrown into the atmosphere producing multi-coloured sunsets caused by the scattering of light by aerosol particles. The paper discusses the ways in which these so-called Krakatoa sunsets, which were experienced by most of the world, were reflected in Victorian scientific and artistic discourse. The accounts included in the section “Descriptions of the Unusual Twilight Glows in Various Parts of the World, in 1883–84” of the Royal Society report The Eruption of Krakatoa and Subsequent Phenomena (1888), and selected poems by Alfred Tennyson, Charles Algernon Swinburne, Robert Bridges, and Mathilde Blind are analyzed to trace Victorian responses to the remarkable optical effects of the Krakatoa eruption.

Towards 3D multiscale adjoint waveform tomography of the crust and upper mantle beneath Southeast Asia

<p>Southeast Asia is one of the most complex tectonic regions on Earth. This is mainly a result of its location within the triple junction of the Australian, Eurasian and Philippine Sea plates which has created a complicated configuration of active plate tectonic boundaries. High plate velocities have generated thousands of kilometers of subducted material and ongoing subduction along the Sunda Arc represents a significant natural hazard (such as the 2004 Sumatra-Andaman earthquake, 2012 Indian Ocean earthquakes and 2018 Anak Krakatoa eruption). However, recent tectonic activity around Borneo may be related to postsubduction processes which could be the key to understanding how the tectonic subduction cycle terminates. Further east, the region is dominated by several minor tectonic plates and the spectacular 180-degree curvature of the Banda Arc. Our work aims to further improve the understanding of this area by providing detailed images of the upper mantle.</p><p>Adjoint waveform tomography is especially suitable for imaging such complex regions. By simulating the 3D wavefield, it is possible to directly compare observed and simulated seismograms, thereby taking into account both body and surface waves. The method can account for the effects of anisotropy, anelasticity, wavefront healing, interference and (de)focusing that can hamper other seismological methods, and is thus especially suitable for strongly heterogenous areas such as Southeast Asia.</p><p>To date, sparse instrument coverage in the region has contributed to a heterogeneous path coverage. In this project, we make use of publicly available data as well as our recently deployed networks of broadband seismometers on Borneo and Sulawesi. This, in addition to access to national permanent networks promises a significant improvement in data coverage around the Banda Arc, Borneo and Sulawesi, thereby providing new opportunities to untangle the region’s complexity.</p><p>We compiled a catalogue of well-constrained earthquakes, optimising for coverage, signal-to-noise ratio and data availability across a wide frequency band, and compared our observed data to synthetics generated from an initial model. In the first part of the inversion, we use long periods of 100 - 150 s to update our initial model using a gradient-based optimisation scheme. We use adjoint methods to obtain sensitivity kernels as the corresponding gradients and initial results will be documented in this presentation. In subsequent iterations, we permit increasingly shorter periods in order to progressively recover finer scales structure and avoid cycle skipping issues.</p>

The Existence of Gamelan, Kampong and Mount Krakatoa Eruption Fundraising in Amsterdam Exhibition in 1883

In 1883, the gamelan, village, and socio-cultural activities of the Dutch East Indies were publicly displayed directly at the De Internationale Koloniale en Uitvoerhandel Tentoonstelling event in Amsterdam. The Dutch East Indies, represented by a group from Parakan Salak, Sukabumi - West Java introduced colonial land cultural entities for six months.Even though they had to deal with the ethnocentrism view that is still strong in European society.However, the performance was carried out by them as good as possible. Their success was accepted by Amsterdam people when there was an eruption of Mount Krakatoa in the Dutch East Indies. The European community and the group of Parakan Salak work together to raise funds for Mount Krakatoa victim.One of them was through a charity performance that presents gamelan and dances.The existence of the art of the colonial land community was able to gather unity to achieve a single goal, there was no more caste differences, between the colonialist and the people of the colony. All are united in the name of humanity.