In this study, we use measurements from over 4,735 globally distributed Global Navigation Satellite System receivers to track the progression of traveling ionospheric disturbances (TIDs) associated with the 15 January 2022 Hunga Tonga‐Hunga Ha'apai submarine volcanic eruption. We identify two distinct Large Scale traveling ionospheric disturbances (LSTIDs) and several subsequent Medium Scale traveling ionospheric disturbances (MSTIDs) that propagate radially outward from the eruption site. Within 3,000 km of epicenter, LSTIDs of >1,600 km wavelengths are initially observed propagating at speeds of ∼950 and ∼555 ms−1, before substantial slowing to ∼600 and ∼390 ms−1, respectively. MSTIDs with speeds of 200–400 ms−1 are observed for 6 hrs following eruption, the first of which comprises the dominant global ionospheric response and coincides with the atmospheric surface pressure disturbance associated with the eruption. These are the first results demonstrating the global impact of the Tonga eruption on the ionospheric state.

The Middle Pliocene ( approximately 3 million years ago) has been identified as the last time the Earth was significantly warmer than it was during the Last Interglacial and Holocene. A quantitative micropaleontological paleotemperature transect from equator to high latitudes in the North Atlantic indicates that Middle Pliocene warmth involved increased meridional oceanic heat transport.

The migration of thermophilic marine Ostracoda into the Arctic Ocean during the Pliocene indicates that winter and summer ocean temperatures around Arctic margins were > 0 øC and > 3 øC, respectively, and that ice-free conditions existed for most or all of the Arctic. By at least 3.5-3.0 Ma, probably earlier, the opening of the Bering Strait allowed marine organisms to migrate through the Arctic Ocean, mostly from the Pacific Ocean. Migrant taxa such as Cythere, Hemicythere, and Neomonoceratina are known from Pliocene deposits of Alaska and Canada as well as Neogene deposits of the North Pacific and Atlantic oceans. On the basis of ecological and zoogeographic information on ostracode species from more than 800 modern "core top" samples for the North Atlantic, North Pacific, and Arctic Oceans, we determined winter and summer temperature tolerances for migrant taxa to be at or above about 0 øC and 3 øC. This suggests ice-free summers, and probably, a perennially ice-free Arctic Ocean in some regions. Elevated water temperatures in the Arctic Ocean between 3.5 and 2.0 Ma is supported by evidence for late Pliocene increased meridional heat transport in the North Ariantic Ocean.Paper number 93PA00060. 0883-8305/93/93PA-00060510.00 INTRODUCTIONThe Arctic Ocean, in general, and Arctic sea ice, in particular, play an important but poorly understood role in oceanic circulation and global climate. Raymo et al. [1990] conducted an experiment using the GISS II atmospheric general circulation model (GCM) to examine the influence of reduced Arctic sea ice, a situation postulated for the Pliocene, on global climate. Among their conclusions, they suggested that late Pliocene cooling, well documented in the North Atlantic deep-sea record and many other paleoclimate proxy records, may have been linked in part to a shift in the Arctic Ocean from perennially ice-free to ice-covered conditions. However, they conclude that paleoclimate evidence from the Arctic is still too fragmentary to identify the forcing mechanisms that changed late Pliocene climate.Perhaps equally important as its influence on atmospheric parameters, Arctic Ocean sea ice contributes in a significant way to deepwater formation and the overall thermohaline circulation of the world's oceans [Aagaard, 1981; Aagaard et al., 1991; Rudels et al., 1991]. Freezing of sea ice and brine rejection in Arctic shelf seas leads to the formation of cold, dense water [Aagaard et al., 1985] and the maintenance of the modem Arctic Ocean halocline [Aagaard, 1981], which serves a key role as a heat sink and which buffers Arctic sea ice from underlying warm Arctic Intermediate Water (AIW) = (the Ariantic layer). A catastrophic breakdown of the halocline may have occurred during Termination I when rapid runoff lowered salinity so much that convection and deep ventilation stopped [Rooth, 1982; Broecker et al., 1985], Smaller-scale oscillations in fresh water from sea ice over historical times can similarly alter convection and deepwater formation [Aagaard and Carmack, 1989] because th...

Neither the ground around a tunnel nor, usually, the tunnel lining, behaves in an elastic manner. Nevertheless, the linear characteristic of an elastic or visco-elastic analysis has great merit, particularly when, as frequently occurs, limitations of knowledge of the behaviour of the ground do not justify greater elaboration. This Paper sets out to establish the loading on a circular tunnel in the ‘elliptical’ mode of deformation, making certain simplifying assumptions. The effects of shear forces between ground and lining are first ignored and subsequently introduced in an explicit manner. Bending moments in a lining are related to a stiffness factor, Rs. While a higher mode of deformation of a tunnel lining is only applicable to problems of stability for thin linings, nevertheless, consideration of this condition allows the coefficient of ground reaction &amda; to be evaluated for conditions of asymmetrical deformation. Direct radial loading of a tunnel lining is related to its compressibility factor Rc. The component of radial loading caused by migration of water towards the tunnel is also established. Some aspects of application of the method are discussed including the effects of joints in a lining and the benefits established on account of the deliberate variation of Rc. The method has serious limitations but frequently serves as a first, and very useful, indication of the relative importance of the principal factors, prior to a more refined analysis. An important point, frequently overlooked, concerns the effect of variation of Poisson's ratio of the ground as loads change, which may greatly affect the stress distribution in the ground and, in consequence, the loads on the lining. Ni le terrain autour du tunnel, ni généralement le tunnel proprement dit, ne se comportent d'une manière élastique. Néanmoins, les caractéristiques linéaires d'une analyse élastique ou visco-élastique ont beaucoup de mérite, particulièrement quand, comme cela arrive fréquemment, les limitations des connaissances du comportement du sol ne justifient pas une plus grande précision. Cette communication tente d'établir le chargement sur un tunnel circulaire se déformant d'une manièrc elliptique en faisant certaines simplifications dans les hypothèses. Les forces de cisaillement entre le sol et le tunnel sont en première phase ignorées et ensuite introduites d'une manière explicite. Les moments fléchissants dans la voûte sont reliés à un coefficient de raideur Rs. Alors qu'un mode de déformation plus important d'une voûte de tunnel est seulement applicable aux problèmes de stabilité des tunnels minces, on considère néanmoins que cette condition conduit à un coefficient de réaction du sol &amda; évalué pour les conditions de déformation asymétrique. Le chargement direct radial d'un tunnel est relié à son facteur de compressibilité Ro. La composante de la charge radiale provoquée par la migration de l'eau vers le tunnel est aussi établie. Quelques aspects de l'application de la méthode sont discutés y compris les effets des joints dans un tunnel et le bénéfice résultant de la prise en compte des variations délibérées de Rc. La méthode a de sérieuses limitations, mais sert fréquemment comme première et très utile indication pour mettre en évidence l'importance relative des principaux facteurs avant une analyse plus raffinée. Un point important, fréquemment négligé, concerne les effets de variation du coefficient de Poisson du sol lors des modifications de charges, ce qui peut gravement affecter la distribution des contraintes dans le sol et en conséquence les charges sur lc tunnel.

We report the results of a multi-instrument, multi-technique, coordinated study of the solar eruptive event of 13 May 2005. We discuss the resultant Earth-directed (halo) coronal mass ejection (CME), and the effects on the terrestrial space environment and upper Earth atmosphere. The interplanetary CME (ICME) impacted the Earth's magnetosphere and caused the most-intense geomagnetic storm of 2005 with a Disturbed Storm Time (Dst) index reaching −263 nT at its peak. The terrestrial environment responded to the storm on a global scale. We have combined observations and measurements from coronal and interplanetary remote-sensing instruments, interplanetary and near-Earth in-situ measurements, remote-sensing observations and in-situ measurements of the terrestrial magnetosphere and ionosphere, along with coronal and heliospheric modelling. These analyses are used to trace the origin, development, propagation, terrestrial impact, and subsequent consequences of this event to obtain the most comprehensive view of a geo-effective solar eruption to date. This particular event is also part of a NASA-sponsored Living With a Star (LWS) study and an on-going US NSF-sponsored Solar, Heliospheric, and INterplanetary Environment (SHINE) community investigation.