scholarly journals Influence of variability to coastline dynamic in the small uninhabited reef islands of Kepulauan Seribu

2021 ◽  
Vol 925 (1) ◽  
pp. 012039
Author(s):  
D A Utami ◽  
I P Anwar ◽  
K A Sujatmiko
Keyword(s):  
Climate Variability ◽  
Anthropogenic Impacts ◽  
Sediment Supply ◽  
Sediment Flux ◽  
Weather Forecasts ◽  
Coastal Resilience ◽  
Reef Islands ◽  
Interannual Climate Variability ◽  
Monsoon Wind ◽  
Wind Cycle

Abstract Small reef islands provide habitable land for coastal communities in many parts of the world. However, the small, low lying reef islands are commonly considered among the most geomorphically sensitive landforms to changes in sea level, wave processes, sediment supply and anthropogenic impacts. Kepulauan Seribu in the Java Sea comprise of numerous reef islands. By 2019, the islands chain is host to more than 24 thousand people. Kepulauan Seribu is affected by monsoon wind cycle. The monsoon wind also known to interact with an interannual phenomenon such as Indian Ocean Dipole (IOD) which affecting regional and local wind circulation. This study aims to examine the reef shoreline response to seasonal and interannual climate variability using satellite data that encompasses yearly monsoon cycle and IOD event. Strengthens (weakens) of winds speed in the study area during the East (West) Monsoon, which in some year also coincides with a positive (negative) IOD event, are observed from 2009 to 2018 ERA - Interim by The European Centre for Medium - Range Weather Forecasts (ECMWF) data. This variability influences the shoreline shifting in the uninhabited reef islands of Kepulauan Seribu as identified based on satellite imagery analysis. More pronounce shifted of large sediment flux are perceptible on opposing monsoon which coincides with positive/negative IOD event. Small uninhabited reef islands have ecological and economical value. Hence, enhancing coastal resilience from erosion by using conservation-types approach should be taking into consideration. Ultimately, a good understanding of climate variability that controlled changes in beach systems of reef islands is important for adequate coastal management decisions.

Feasibility of sedimentation strategies for the Mekong delta to counterbalance relative sea-level rise

2021 ◽  
Author(s):  
Frances E. Dunn ◽  
Philip S. J. Minderhoud
Keyword(s):  
Land Use ◽  
Sea Level Rise ◽  
Sea Level ◽  
Mekong Delta ◽  
Sediment Deposition ◽  
Sediment Supply ◽  
Sediment Flux ◽  
Relative Sea Level ◽  
Fluvial Sediment ◽  
Relative Sea Level Rise

<p>As one of the largest deltas in the world, the Mekong delta is home to over 17 million people and supports internationally important agriculture. Recently deposited sediment compacts and causes subsidence in deltas, so they require regular sediment input to maintain elevation relative to sea level. These processes are complicated by human activities, which prevent sediment deposition indirectly through reducing fluvial sediment supply and directly through the construction of flood defence infrastructure on deltas, impeding floods which deliver sediment to the land. Additionally, anthropogenic activities increase the rate of subsidence through the extraction of groundwater and other land-use practices.</p><p>This research shows the potential for fluvial sediment delivery to compensate for sea-level rise and subsidence in the Mekong delta over the 21st century. We use detailed elevation data and subsidence scenarios in combination with regional sea-level rise and fluvial sediment flux projections to quantify the potential for maintaining elevation relative to sea level in the Mekong delta. We present four examples of localised sedimentation scenarios in specific areas, for which we quantified the potential effectiveness of fluvial sediment deposition for offsetting relative sea-level rise. The presented sediment-based adaptation strategies are complicated by existing land use, therefore a change in water and sediment management is required to effectively use natural resources and employ these adaptation methods. The presented approach could be an exemplar to assess sedimentation strategy feasibility in other delta systems worldwide that are under threat from sea-level rise.</p>

scholarly journals Simulated rice yields as affected by interannual climate variability and possible climate change in Java

1999 ◽  
Vol 12 ◽  
pp. 145-152 ◽  
Author(s):  
I Amien ◽  
P Redjekiningrum ◽  
B Kartiwa ◽  
W Estiningtyas
Keyword(s):  
Climate Change ◽  
Climate Variability ◽  
Rice Yields ◽  
Interannual Climate Variability

Eastward Shift of Interannual Climate Variability in the South Indian Ocean since 1950

2021 ◽  
pp. 1-46
Author(s):  
Lei Zhang ◽  
Weiqing Han ◽  
Kristopher B. Karnauskas ◽  
Yuanlong Li ◽  
Tomoki Tozuka
Keyword(s):  
Indian Ocean ◽  
Climate Variability ◽  
Decadal Variability ◽  
Dominant Role ◽  
Tropical Pacific ◽  
The South ◽  
South Indian Ocean ◽  
Climate Modes ◽  
South Indian ◽  
Interannual Climate Variability

AbstractThe subtropical Indian Ocean Dipole (SIOD) and Ningaloo Niño are the two dominant modes of interannual climate variability in the subtropical South Indian Ocean. Observations show that the SIOD has been weakening in the recent decades, while Ningaloo Niño has been strengthening. In this study, we investigate the causes for such changes by analyzing climate model experiments using the NCAR Community Earth System Model version 1 (CESM1). Ensemble-mean results from CESM1 large-ensemble (CESM1-LE) suggest that the external forcing causes negligible changes in the amplitudes of the SIOD and Ningaloo Niño, suggesting a dominant role of internal climate variability. Meanwhile, results from CESM1 pacemaker experiments reveal that the observed changes in the two climate modes cannot be attributed to the effect of sea surface temperature anomalies (SSTA) in either the tropical Pacific or tropical Indian Oceans. By further comparing different ensemble members from the CESM1-LE, we find that a Warm Pool Dipole mode of decadal variability, with opposite SSTA in the southeast Indian Ocean and the western-central tropical Pacific Ocean plays an important role in driving the observed changes in the SIOD and Ningaloo Niño. These changes in the two climate modes have considerable impacts on precipitation and sea level variabilities in the South Indian Ocean region.

Determination of seasonal forecast skill in identifying extreme events of temperature, wind speed, and SPI

2021 ◽  
Author(s):  
Massimiliano Palma ◽  
Franco Catalano ◽  
Irene Cionni ◽  
Marcello Petitta
Keyword(s):  
Climate Change ◽  
Wind Speed ◽  
Climate Variability ◽  
Extreme Events ◽  
Bias Correction ◽  
Skill Score ◽  
Seasonal Forecast ◽  
Energy Sector ◽  
Seasonal Forecasts ◽  
Weather Forecasts

<p>Renewable energy is the fastest-growing source of electricity globally, but climate variability and impacting events affecting the potential productivity of plants are obstacles to its integration and planning. Knowing a few months in advance the productivity of plants and the impact of extreme events on productivity and infrastructure can help operators and policymakers make the energy sector more resilient to climate variability, promoting the deployment of renewable energy while maintaining energy security.</p><p>The energy sector already uses weather forecasts up to 15 days for plant management; beyond this time horizon, climatologies are routinely used. This approach has inherent weaknesses, including the inability to predict extreme events, the prediction of which is extremely useful to decision-makers. Information on seasonal climate variability obtained through climate forecasts can be of considerable benefit in decision-making processes. The Climate Data Store of the Copernicus Climate Change Service (C3S) provides seasonal forecasts and a common period of retrospective simulations (hindcasts) with equal spatial temporal resolution for simulations from 5 European forecast centres (European Centre for Medium-Range Weather Forecasts (ECMWF), Deutscher Wetterdienst (DWD), Meteo France (MF), UK Met Office (UKMO) and Euro-Mediterranean Centre on Climate Change (CMCC)), one US forecasting centre (NCEP) plus the Japan Meteorological Agency (JMA) model.</p><p>In this work, we analyse the skill and the accuracy of a subset of the operational seasonal forecasts provided by Copernicus C3S, focusing on three relevant essential climate variables for the energy sector: temperature (t2m), wind speed (sfcWind, relevant to the wind energy production), and precipitation. The latter has been analysed by taking the Standard Precipitation Index (SPI) into account.</p><p>First, the methodologies for bias correction have been defined. Subsequently, the reliability of the forecasts has been assessed using appropriate reliability indicators based on comparison with ERA5 reanalysis dataset. The hindcasts cover the period 1993-2017. For each of the variables considered, we evaluated the seasonal averages based on monthly means for two seasons: winter (DJF) and summer (JJA). Data have been bias corrected following two methodologies, one based on the application of a variance inflation technique to ensure the correction of the bias and the correspondence of variance between forecast and observation; the other based on the correction of the bias, the overall forecast variance and the ensemble spread as described in Doblas-Reyes et al. (2005).</p><p>Predictive ability has been assessed by calculating binary (Brier Skill Score, BSS hereafter, and Ranked Probability Skill Score, RPSS hereafter) and continuous (Continuous Ranked Probability Skill Score, CRPSS hereafter) scores. Forecast performance has been assessed using ERA 5 reanalysis as pseudo-observations. </p><p>In this work we discuss the results obtained with different bias correction techniques highlighting the outcomes obtained analyzing the BSS for the first and the last terciles and the first and the last percentiles (10th and 90th). This analysis has the goal to identify the regions in which the seasonal forecast can be used to identify potential extreme events.</p>

Links between interannual climate variability and marine ecosystems in the Tropical Atlantic

2021 ◽  
Author(s):  
Emilia Sanchez ◽  
Marta Martin Rey ◽  
Roland Seferian ◽  
Yeray Santana-Falcon
Keyword(s):  
Climate Variability ◽  
Climate Models ◽  
Coastal Upwelling ◽  
Net Primary Production ◽  
Surface Wind ◽  
Marine Ecosystems ◽  
Tropical Atlantic ◽  
Coupled Modes ◽  
Future Evolution ◽  
Interannual Climate Variability

<p>The interannual climate variability in the Tropical Atlantic is mainly controlled by two air-sea coupled modes denoted as Meridional Mode (MM) and Equatorial Mode (EM). The MM, peaking in boreal spring, is characterized by an anomalous Sea Surface Temperature (SST) interhemispheric gradient associated with anomalous surface cross-equatorial winds blowing to the warmer hemisphere.  On the other hand, the positive phase of the EM exhibits an anomalous warming in the equatorial band and along the African coast, related to a weakening of the climatological trade winds. Both interannual modes illustrate significant SST and surface wind changes in the eastern boundary upwelling systems (EBUS) of the tropical Atlantic: the Senegal-Mauritanian and Angola-Benguela. The EBUS are characterized by wind-induced coastal upwelling of deep cold waters rich in nutrients supporting high primary productivity and an abundance of food resources. Hence, the physical or climate characteristics associated with the MM and EM may have a potential effect on marine organisms and ecosystems. The goal of this study is to understand the links between the main modes of tropical Atlantic variability and biogeochemical (BGC) variables such as oxygen, net primary production and ph. These are known to be the main drivers for marine ecosystems. Firstly we study the influence of MM and AM on the EBUS and how these links are represented by the coupled ESM CNRM-ESM2.1 against observations. Second, we use the ESM to investigate the links between the SST anomalies associated to MM and EM and the main BGC stressors mentioned above. For this purpose, a set of numerical experiments performed with CMIP6 climate models are used. This work is supported by the H2020 TRIATLAS project, whose main goal is to understand and evaluate the future evolution of living marine resources in the Atlantic Ocean.</p>

scholarly journals Bedrock incision by bedload: insights from direct numerical simulations

2016 ◽  
Author(s):  
Guilhem Aubert ◽  
Vincent J. Langlois ◽  
Pascal Allemand
Keyword(s):  
Numerical Approach ◽  
Sediment Supply ◽  
Sediment Flux ◽  
Analytical Models ◽  
Water Stream ◽  
Direct Measurements ◽  
Bedload Sediment ◽  
Discrete Element Simulations ◽  
High Sediment

Abstract. Bedload sediment transport is one of the main processes that contribute to bedrock incision in a river and is therefore one of the key control parameters in the evolution of mountainous lanscapes. In recent years, many studies have addressed this issue through experimental setups, direct measurements in the field or various analytical models. In this article, we present a new direct numerical approach: using the classical methods of discrete element simulations applied to granular materials, we compute explicitely the trajectories of a number of pebbles entrained by a turbulent water stream over a rough solid surface. This method allows us to extract quantitatively the amount of energy that successive impacts of pebbles deliver to the bedrock, as a function of both the amount of sediment available and the Shields number. We show that we reproduce qualitatively the behaviour observed experimentally by Sklar and Dietrich (2001) and observe both a "tool-effect" and a "cover- effect". Converting the energy delivered to the bedrock into an average long-term incision rate of the river leads to predictions consistent with observations in the field. Finally, we reformulate the dependency of this incision rate with Shields number and sediment flux, and predict that the cover term should decay linearly at low sediment supply and exponentially at high sediment supply.

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