The Mesoscale Response to Global Warming over the Pacific Northwest Evaluated Using a Regional Climate Model Ensemble

This paper describes the downscaling of an ensemble of twelve GCMs using the WRF model at 12-km grid spacing over the period 1970-2099, examining the mesoscale impacts of global warming as well as the uncertainties in its mesoscale expression. The RCP 8.5 emissions scenario was used to drive both global and regional climate models. The regional climate modeling system reduced bias and improved realism for a historical period, in contrast to substantial errors for the GCM simulations driven by lack of resolution. The regional climate ensemble indicated several mesoscale responses to global warming that were not apparent in the global model simulations, such as enhanced continental interior warming during both winter and summer as well as increasing winter precipitation trends over the windward slopes of regional terrain, with declining trends to the lee of major barriers. During summer there is general drying, except to the east of the Cascades. April 1 snowpack declines are large over the lower to middle slopes of regional terrain, with small snowpack increases over the lower elevations of the interior. Snow-albedo feedbacks are very different between GCM and RCM projections, with the GCM’s producing large, unphysical areas of snowpack loss and enhanced warming. Daily average winds change little under global warming, but maximum easterly winds decline modestly, driven by a preferential sea level pressure decline over the continental interior. Although temperatures warm continuously over the domain after approximately 2010, with slight acceleration over time, occurrences of temperature extremes increase rapidly during the second half of the 21st century.

Regional Morpho-Kinematic Inventory of Slope Movements in Northern Norway

Mountain slopes in periglacial environments are affected by frost- and gravity-driven processes that shape the landscape. Both rock glaciers and rockslides have been intensively inventoried worldwide. Although most inventories are traditionally based on morphologic criteria, kinematic approaches based on satellite remote sensing have more recently been used to identify moving landforms at the regional scale. In this study, we developed simplified Interferometric Synthetic Aperture Radar (InSAR) products to inventory ground velocity in a region in Northern Norway covering approximately 7,500 km2. We used a multiple temporal baseline InSAR stacking procedure based on 2015–2019 ascending and descending Sentinel-1 images to take advantage of a large set of interferograms and exploit different detection capabilities. First, moving areas are classified according to six velocity brackets, and morphologically associated to six landform types (rock glaciers, rockslides, glaciers/moraines, talus/scree deposits, solifluction/cryoturbation and composite landforms). The kinematic inventory shows that the velocity ranges and spatial distribution of the different types of slope processes vary greatly within the study area. Second, we exploit InSAR to update pre-existing inventories of rock glaciers and rockslides in the region. Landform delineations and divisions are refined, and newly detected landforms (54 rock glaciers and 20 rockslides) are incorporated into the databases. The updated inventories consist of 414 rock glacier units within 340 single- or multi-unit(s) systems and 117 rockslides. A kinematic attribute assigned to each inventoried landform documents the order of magnitude of the creep rate. Finally, we show that topo-climatic variables influence the spatial distribution of the rock glaciers. Their mean elevation increases toward the continental interior with a dominance of relict landforms close to the land-sea margin and an increased occurrence of active landforms further inland. Both rock glaciers and rockslides are mostly located on west-facing slopes and in areas characterised by strongly foliated rocks, which suggests the influence of geological preconditioning factors. The study demonstrates the value of semi-quantitative InSAR products to characterise kinematic information at large scale and exploit the results for periglacial research. It highlights the complementarity of both kinematic and morphologic approaches for inventorying slope processes.

Quasi-Love wave scattering reveals tectonic history of Australia and its margins reflected by mantle anisotropy

The Australian continental crust preserves a rich geological history, but it is unclear to what extent this history is expressed deeper within the mantle. Here an investigation of Quasi-Love waves is performed to detect scattering of seismic surface waves at mantle depths (between 100–200 km) by lateral gradients in seismic anisotropy. Across Australasia 275 new observations of Quasi-Love waves are presented. The inferred scattering source and lateral anisotropic gradients are preferentially located either near the passive continental margins, or near the boundaries of major geological provinces within Australia. Pervasive fossilized lithospheric anisotropy within the continental interior is implied, on a scale that mirrors the crustal geology at the surface, and a strong lithosphere that has preserved this signal over billions of years. Along the continental margins, lateral anisotropic gradients may indicate either the edge of the thick continental lithosphere, or small-scale dynamic processes in the asthenosphere below.

The Deep Roots of Geology: Tectonic History of Australia and its Margins expressed by Mantle Anisotropy

The Australian continental crust preserves a rich geological history, but it is unclear to what extent this history is expressed deeper within the mantle. Scattering of surface waves predominantly between 100-200 km depth by lateral gradients in seismic anisotropy, termed Quasi-Love waves, offer potential new insights. Across Australasia over 275 new scatterers are detected, and are found to be preferentially located near (1) the passive continental margins, and (2) the boundaries of major geological provinces within Australia. Such lateral anisotropic gradients imply pervasive fossilized lithospheric anisotropy within the continental interior, on a scale that mirrors the crustal geology at the surface, and a strong lithosphere that preserves this signal over billions of years. Along the continental margins, lateral anisotropic gradients may indicate either the edge of the thick continental lithosphere, or small-scale dynamic processes in the asthenosphere, such as edge-drive convection, tied to the transition from oceanic to continental lithosphere.

Conclusion

The endurance of terrestrial forms of connectivity over the Eurasian continental interior lies at the heart of this book. By reviewing the life of such connections in the twentieth century, this chapter draws out this book’s four major interventions. The first concerns the value of examining long-term patterns of change and the virtue of thinking across such divides as Mughal and British, pre-colonial and colonial. The second relates to the way this book thinks about empires in novel ways, whether by taking a trans-imperial framework or by focussing on the ways non-political entities—such as merchant networks—persisted through periods of imperial flux and the rise and fall of empires. The third is the focus on space, particularly interior or inner-continental space, and its place within global history. The final contribution is to provide an impetus to scholars to think of the synchronicity of multiple forms of globalisation and their interrelation.

Introduction

The recent return to terrestrial forms of connectivity over long distances, not least in the wake of China’s inauguration of the ‘Belt and Road Initiative’, has renewed interest in the Silk Roads. This chapter explains that the web of routes which connected various parts of Afro-Eurasia persisted throughout the rise of trans-oceanic networks after circa 1500, at which time north-south routes from the Eurasian continental interior into the Indian subcontinent and the Indian Ocean world became more prominent. The history of this remarkable survival is one of the themes of this book. To introduce these themes, this chapter sketches the contours of those states and empires—Mughal, Sikh, Afghan, Safavid, Uzbek, British and Russian—whose fates were tied up with the history of Indo-central Asian caravan trade.

Traders

The eighteenth-century expansion of the Durrani, Qing and Romanov empires deeper into Eurasia brought liquid wealth from the increasingly globalised economy into this space, stimulating commercial opportunities and the closer integration of the continental interior. This chapter uncovers one of the outcomes of this process as the empowerment of new commercial groups. Afghans, Pashtuns and Muslims from the Indo-Afghan frontier—generally seen by scholars only as pastoralists and peddlers—were the entrepreneurial lynchpins of the developments examined in this chapter. As former peddlers harnessed market opportunities and channelled the benefits accrued from political patronage into new business ventures, they accumulated capital and widened the geographic scope of their operations. In so doing, they posed serious competition to established north-Indian magnate groups, while also changing the character of commerce itself.

India and the Silk Roads

India and the Silk Roads is a global history of a continental interior, the first to comprehensively examine the textual and material traces of India’s caravan trade with central Asia. But what was the fate of these overland connections in the ages of sail and steam? This book brings the world of caravan trade to life—a world of merchants, mercenaries, pastoralists and pilgrims, but also of kings, bureaucrats and their subjects in the countryside and towns. Their livelihoods did not become obsolete with the advent of ‘modern’ technologies and the consequent emergence of new global networks. Terrestrial routes remained critically important, not only handling flows of goods and money, but also fostering networks of trade in credit, secret intelligence and fighting power. With the waning of the Mughal Empire during the eighteenth century, new Indian kingdoms and their rulers came to the fore, drawing their power and prosperity from resources brought by caravan trade. The encroachment of British and Russian imperialism into this commercial arena in the nineteenth century gave new significance to some people and flows, while steadily undermining others. By showing how no single ruler could control the nebulous yet durable networks of this trading world, which had its own internal dynamics even as it evolved in step with global transformations, this book forces us to rethink the history of globalisation and re-evaluate our fixation with empires and states as the building blocks of historical analysis.