Coastal morphodynamics in an Arctic fluvial-tidal transition zone in the deglaciated Dicksonfjord, Svalbard

2020 ◽  
Author(s):  
Dohyeong Kim ◽  
Joohee Jo ◽  
Kyungsik Choi
Keyword(s):  
Transition Zone ◽  
Large Scale ◽  
Sediment Flux ◽  
Ice Age ◽  
Aerial Photographs ◽  
Coarse Grained ◽  
The Arctic ◽  
Survey Period ◽  
Sediment Delivery ◽  
Coastal Morphodynamics

<p>Pronounced morphologic changes such as coastal retreat and delta progradation occur widely along the Arctic coastal regions in response to increased sediment flux, freshwater runoff, and wave activity caused by climate changes. Compared to open coast and large-scale deltas in the Arctic region, the coastal morphodynamics and associated sediment transport in the Arctic fluvial-tidal transition zone (FTTZ) are less well understood. A series of recurved spits are developed on the upper intertidal zone of microtidal flats in the FTTZ of deglaciated Dicksonfjorden, Svalbard. The morphodynamics and sediment fluxes of the spit complexes were quantified using unmanned aerial vehicle (UAV)-assisted photogrammetry and Real-Time Kinematic GPS. Repeated annual survey indicates that the spits have elongated at 22 m yr<sup>-1</sup> and have migrated landward at 4.3 m yr<sup>-1</sup> over the last four years. The growth and migration rate of the spits increases seaward, where coastal cliffs consisting of an unconsolidated mixture of angular gravels and muds retreats at 0.2 m yr<sup>-1</sup> with net erosion rate of 0.02 m yr<sup>-1</sup> and provides local sediment source for the spits. In contrast, isolated gravel ridges, i.e., cheniers, on the tidal flats in the further landward did not migrate during the survey period. Archives of aerial photographs indicate that the cheniers had remained stationary since the 1930s, when a shoreline was located near the cheniers. The present study demonstrates that wave-induced overwash and longshore drift of coarse-grained sediments originated from the retreating cliffs are vital to the annual spit morphodynamics even in the innermost part of the fjord. Tidal flat progradation accelerated since the Little Ice Age with global warming trends by increased runoff from snow-fed rivers and alluvial fans, controls the centennial spit morphodynamics and distribution of wave-built morphology in the FTTZ of glacier-free Dicksonfjorden by regulating episodic sediment delivery via a seaward-shift in the locus of wave shoaling.</p>

Evolution of the Ofanto River delta from the ‘Little Ice Age’ to modern times: Implications of large-scale synoptic patterns

The Holocene ◽  
2018 ◽  
Vol 28 (12) ◽  
pp. 1948-1967 ◽  
Author(s):  
Vincenzo De Santis ◽  
Massimo Caldara ◽  
Antonella Marsico ◽  
Domenico Capolongo ◽  
Luigi Pennetta
Keyword(s):  
Large Scale ◽  
Low Pressure ◽  
River Delta ◽  
Ice Age ◽  
Aerial Photographs ◽  
Anthropogenic Factors ◽  
Synoptic Patterns ◽  
Delta Evolution ◽  
Circulation Mode

We reconstruct the evolution of the Ofanto River delta from the 17th century to the present using historical maps (1600–1850), official IGM topographic maps (1850–1980) and recent aerial photographs (2015), and we compare long-term morphological changes with the evolution of the delta of the Volturno River during the same time period. The aim of this study is to define the role of climatic (flood frequency, synoptic pressure patterns) and anthropogenic factors (deforestation, anthropogenic sediment subtraction of river sediment) in the evolution of the Ofanto delta. We analysed the importance of each factor on the evolution of the delta and compared them with the simultaneous behaviour of the Volturno delta to highlight the role of large-scale synoptic pressure patterns. We found that the main driver of different delta evolution phases is weather-climatic condition, while anthropogenic factors interacted with the delta evolution in different ways but did not control the first-order evolution. In particular, analysing the data on recent floods, we found that the most favourable situations for both rivers are omega-blocking, deep low-pressure trough and strong meridional circulation (mode Ω) which create Mediterranean low-pressure systems. Instead, a zonal circulation (mode W) can only cause floods on Volturno. Because the evolution of a delta is driven by the frequency of floods, and because we found that the frequency of floods is guided by synoptic patterns, a relationship can be established between delta evolution and synoptic patterns in the past. Consequently, past phases of the contemporary progradation of the Ofanto and Volturno deltas suggest the increasing frequency of mode Ω, while phases of simultaneous progradation of the Volturno delta and stability and/or retreat of the Ofanto delta are indicative of the increasing frequency of mode W. The only exception occurred during the last evolutionary phase (60 years), when anthropogenic sediment subtraction was prevalent.

scholarly journals Historical glacier outlines from digitized topographic maps of the Swiss Alps

2017 ◽  
Author(s):  
Daphné Freudiger ◽  
David Mennekes ◽  
Jan Seibert ◽  
Markus Weiler
Keyword(s):  
Large Scale ◽  
Swiss Alps ◽  
Ice Age ◽  
Aerial Photographs ◽  
Topographic Maps ◽  
Data Repository ◽  
Glacier Mass Balance ◽  
European Alps ◽  
Glacier Area

Abstract. Since the end of the Little Ice Age around 1850, the total glacier area of the Central European Alps has considerably decreased. In order to understand the changes in glacier coverage at various scales and to model past and future streamflow accurately, long-term and large-scale datasets of glacier outlines are needed. To fill the gap between the morphologically reconstructed glacier outlines from the moraine extent corresponding to the time period around 1850 and the first complete dataset of glacier areas in the Swiss Alps from aerial photographs in 1973, glacier area from 80 sheets of a historical topographic map, so-called Siegfried map, were manually digitized for the publication years 1878–1918 (further called first period, with most sheets being published around 1900) and 1917–1944 (further called second period, with most sheets being published around 1935). The accuracy of the digitized glacier areas was then assessed through a two-step validation process: the data was (1) visually and (2) quantitatively compared to glacier area datasets of the years 1850, 1973, 2003, and 2010, which were derived from different sources. The validation showed that at least 70 % of the digitized glaciers were comparable to the outlines from the other datasets and were therefore plausible. Furthermore, the accuracy of the manual digitization was found to be lower than 5 %. The presented datasets of glacier outlines for the first and second periods were found to be valuable source of information for long-term glacier mass balance or hydrological modelling in glacierized basins if the uncertainty of the historical topographic maps is considered in the interpretation of the results. The datasets can be downloaded from the FreiDok plus data repository (https://freidok.uni-freiburg.de/data/12874, https://doi.org/10.6094/UNIFR/12874).

scholarly journals Historical glacier outlines from digitized topographic maps of the Swiss Alps

2018 ◽  
Vol 10 (2) ◽  
pp. 805-814 ◽  
Author(s):  
Daphné Freudiger ◽  
David Mennekes ◽  
Jan Seibert ◽  
Markus Weiler
Keyword(s):  
Large Scale ◽  
Swiss Alps ◽  
Ice Age ◽  
Aerial Photographs ◽  
Topographic Maps ◽  
Glacier Mass Balance ◽  
European Alps ◽  
Glacier Area ◽  
Basin Scale

Abstract. Since the end of the Little Ice Age around 1850, the total glacier area of the central European Alps has considerably decreased. In order to understand the changes in glacier coverage at various scales and to model past and future streamflow accurately, long-term and large-scale datasets of glacier outlines are needed. To fill the gap between the morphologically reconstructed glacier outlines from the moraine extent corresponding to the time period around 1850 and the first complete dataset of glacier areas in the Swiss Alps from aerial photographs in 1973, glacier areas from 80 sheets of a historical topographic map (the Siegfried map) were manually digitized for the publication years 1878–1918 (further called first period, with most sheets being published around 1900) and 1917–1944 (further called second period, with most sheets being published around 1935). The accuracy of the digitized glacier areas was then assessed through a two-step validation process: the data were (1) visually and (2) quantitatively compared to glacier area datasets of the years 1850, 1973, 2003, and 2010, which were derived from different sources, at the large scale, basin scale, and locally. The validation showed that at least 70 % of the digitized glaciers were comparable to the outlines from the other datasets and were therefore plausible. Furthermore, the inaccuracy of the manual digitization was found to be less than 5 %. The presented datasets of glacier outlines for the first and second periods are a valuable source of information for long-term glacier mass balance or hydrological modelling in glacierized basins. The uncertainty of the historical topographic maps should be considered during the interpretation of the results. The datasets can be downloaded from the FreiDok plus data repository (https://freidok.uni-freiburg.de/data/15008, https://doi.org/10.6094/UNIFR/15008).

Classification of vegetation in Cucphuong National Park with the aim of large-scale mapping, Vietnam

1996 ◽  
pp. 64-67 ◽  
Author(s):  
Nguen Nghia Thin ◽  
Nguen Ba Thu ◽  
Tran Van Thuy
Keyword(s):  
National Park ◽  
Large Scale ◽  
Satellite Images ◽  
Field Work ◽  
Aerial Photographs ◽  
Vegetation Map ◽  
Dense Forest ◽  
Broad Leaved Forest ◽  
Leaved Forest

The tropical seasonal rainy evergreen broad-leaved forest vegetation of the Cucphoung National Park has been classified and the distribution of plant communities has been shown on the map using the relations of vegetation to geology, geomorphology and pedology. The method of vegetation mapping includes: 1) the identifying of vegetation types in the remote-sensed materials (aerial photographs and satellite images); 2) field work to compile the interpretation keys and to characterize all the communities of a study area; 3) compilation of the final vegetation map using the combined information. In the classification presented a number of different level vegetation units have been identified: formation classes (3), formation sub-classes (3), formation groups (3), formations (4), subformations (10) and communities (19). Communities have been taken as mapping units. So in the vegetation map of the National Park 19 vegetation categories has been shown altogether, among them 13 are natural primary communities, and 6 are the secondary, anthropogenic ones. The secondary succession goes through 3 main stages: grassland herbaceous xerophytic vegetation, xerophytic scrub, dense forest.

scholarly journals Mean-Field Models for EEG/MEG: From Oscillations to Waves

2021 ◽  
Author(s):  
Áine Byrne ◽  
James Ross ◽  
Rachel Nicks ◽  
Stephen Coombes
Keyword(s):  
Gap Junction ◽  
Large Scale ◽  
Mean Field ◽  
Coarse Grained ◽  
Neural Mass Model ◽  
Neuron Network ◽  
Mass Model ◽  
Mean Field Model ◽  
Neural Mass ◽  
The Rich

AbstractNeural mass models have been used since the 1970s to model the coarse-grained activity of large populations of neurons. They have proven especially fruitful for understanding brain rhythms. However, although motivated by neurobiological considerations they are phenomenological in nature, and cannot hope to recreate some of the rich repertoire of responses seen in real neuronal tissue. Here we consider a simple spiking neuron network model that has recently been shown to admit an exact mean-field description for both synaptic and gap-junction interactions. The mean-field model takes a similar form to a standard neural mass model, with an additional dynamical equation to describe the evolution of within-population synchrony. As well as reviewing the origins of this next generation mass model we discuss its extension to describe an idealised spatially extended planar cortex. To emphasise the usefulness of this model for EEG/MEG modelling we show how it can be used to uncover the role of local gap-junction coupling in shaping large scale synaptic waves.

scholarly journals Effects of Climatic Drivers and Teleconnections on Late 20th Century Trends in Spring Freshet of Four Major Arctic-Draining Rivers

Water ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 179
Author(s):  
Roxanne Ahmed ◽  
Terry Prowse ◽  
Yonas Dibike ◽  
Barrie Bonsal
Keyword(s):  
Arctic Ocean ◽  
Large Scale ◽  
Southern Oscillation ◽  
Rate Of Change ◽  
The Arctic ◽  
Late 20Th Century ◽  
Basin Scale ◽  
The Arctic Ocean ◽  
Spring Freshet ◽  
Climatic Drivers

Spring freshet is the dominant annual discharge event in all major Arctic draining rivers with large contributions to freshwater inflow to the Arctic Ocean. Research has shown that the total freshwater influx to the Arctic Ocean has been increasing, while at the same time, the rate of change in the Arctic climate is significantly higher than in other parts of the globe. This study assesses the large-scale atmospheric and surface climatic conditions affecting the magnitude, timing and regional variability of the spring freshets by analyzing historic daily discharges from sub-basins within the four largest Arctic-draining watersheds (Mackenzie, Ob, Lena and Yenisei). Results reveal that climatic variations closely match the observed regional trends of increasing cold-season flows and earlier freshets. Flow regulation appears to suppress the effects of climatic drivers on freshet volume but does not have a significant impact on peak freshet magnitude or timing measures. Spring freshet characteristics are also influenced by El Niño-Southern Oscillation, the Pacific Decadal Oscillation, the Arctic Oscillation and the North Atlantic Oscillation, particularly in their positive phases. The majority of significant relationships are found in unregulated stations. This study provides a key insight into the climatic drivers of observed trends in freshet characteristics, whilst clarifying the effects of regulation versus climate at the sub-basin scale.

scholarly journals Simba

2021 ◽  
Vol 64 (6) ◽  
pp. 107-116
Author(s):  
Yakun Sophia Shao ◽  
Jason Cemons ◽  
Rangharajan Venkatesan ◽  
Brian Zimmer ◽  
Matthew Fojtik ◽  
...  
Keyword(s):  
Deep Learning ◽  
Large Scale ◽  
Data Locality ◽  
Coarse Grained ◽  
Batch Size ◽  
Peak Performance ◽  
Large Scale Systems ◽  
High Area ◽  
On Chip ◽  
And Storage

Package-level integration using multi-chip-modules (MCMs) is a promising approach for building large-scale systems. Compared to a large monolithic die, an MCM combines many smaller chiplets into a larger system, substantially reducing fabrication and design costs. Current MCMs typically only contain a handful of coarse-grained large chiplets due to the high area, performance, and energy overheads associated with inter-chiplet communication. This work investigates and quantifies the costs and benefits of using MCMs with finegrained chiplets for deep learning inference, an application domain with large compute and on-chip storage requirements. To evaluate the approach, we architected, implemented, fabricated, and tested Simba, a 36-chiplet prototype MCM system for deep-learning inference. Each chiplet achieves 4 TOPS peak performance, and the 36-chiplet MCM package achieves up to 128 TOPS and up to 6.1 TOPS/W. The MCM is configurable to support a flexible mapping of DNN layers to the distributed compute and storage units. To mitigate inter-chiplet communication overheads, we introduce three tiling optimizations that improve data locality. These optimizations achieve up to 16% speedup compared to the baseline layer mapping. Our evaluation shows that Simba can process 1988 images/s running ResNet-50 with a batch size of one, delivering an inference latency of 0.50 ms.

scholarly journals Arctic Ocean stratification set by sea level and freshwater inputs since the last ice age

2021 ◽  
Author(s):  
Jesse R. Farmer ◽  
Daniel M. Sigman ◽  
Julie Granger ◽  
Ona M. Underwood ◽  
François Fripiat ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Surface Waters ◽  
Ice Age ◽  
The Arctic ◽  
Bering Strait ◽  
Central Arctic Ocean ◽  
Phytoplankton Productivity ◽  
Nitrate Consumption ◽  
Western Arctic ◽  
Last Ice Age

AbstractSalinity-driven density stratification of the upper Arctic Ocean isolates sea-ice cover and cold, nutrient-poor surface waters from underlying warmer, nutrient-rich waters. Recently, stratification has strengthened in the western Arctic but has weakened in the eastern Arctic; it is unknown if these trends will continue. Here we present foraminifera-bound nitrogen isotopes from Arctic Ocean sediments since 35,000 years ago to reconstruct past changes in nutrient sources and the degree of nutrient consumption in surface waters, the latter reflecting stratification. During the last ice age and early deglaciation, the Arctic was dominated by Atlantic-sourced nitrate and incomplete nitrate consumption, indicating weaker stratification. Starting at 11,000 years ago in the western Arctic, there is a clear isotopic signal of Pacific-sourced nitrate and complete nitrate consumption associated with the flooding of the Bering Strait. These changes reveal that the strong stratification of the western Arctic relies on low-salinity inflow through the Bering Strait. In the central Arctic, nitrate consumption was complete during the early Holocene, then declined after 5,000 years ago as summer insolation decreased. This sequence suggests that precipitation and riverine freshwater fluxes control the stratification of the central Arctic Ocean. Based on these findings, ongoing warming will cause strong stratification to expand into the central Arctic, slowing the nutrient supply to surface waters and thus limiting future phytoplankton productivity.

scholarly journals Mobility patterns are associated with experienced income segregation in large US cities

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Esteban Moro ◽  
Dan Calacci ◽  
Xiaowen Dong ◽  
Alex Pentland
Keyword(s):  
Large Scale ◽  
Mobility Model ◽  
Coarse Grained ◽  
Spatial Proximity ◽  
Mobility Patterns ◽  
Data Set ◽  
Residential Patterns ◽  
Income Segregation ◽  
Mobility Data ◽  
Mobility Behavior

AbstractTraditional understanding of urban income segregation is largely based on static coarse-grained residential patterns. However, these do not capture the income segregation experience implied by the rich social interactions that happen in places that may relate to individual choices, opportunities, and mobility behavior. Using a large-scale high-resolution mobility data set of 4.5 million mobile phone users and 1.1 million places in 11 large American cities, we show that income segregation experienced in places and by individuals can differ greatly even within close spatial proximity. To further understand these fine-grained income segregation patterns, we introduce a Schelling extension of a well-known mobility model, and show that experienced income segregation is associated with an individual’s tendency to explore new places (place exploration) as well as places with visitors from different income groups (social exploration). Interestingly, while the latter is more strongly associated with demographic characteristics, the former is more strongly associated with mobility behavioral variables. Our results suggest that mobility behavior plays an important role in experienced income segregation of individuals. To measure this form of income segregation, urban researchers should take into account mobility behavior and not only residential patterns.

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