Monsoons: global energetics and local physics as drivers of past, present and future monsoons

Global constraints on momentum and energy govern the structure of the zonal mean tropical circulation and rainfall. The continental-scale monsoon systems are also facets of a momentum- and energy-constrained global circulation, but their modern and paleo variability deviates substantially from that of the longitudinal mean through mechanisms neither fully understood nor well simulated. A framework grounded in global constraints yet encompassing the complexities of monsoon dynamics is needed to identify the causes of mismatch between theory, models, and observations and, ultimately, improve regional climate projection. In a first step towards this goal, disparate regional processes must be distilled into gross measures of energy flow in and out of continents and from the surface to the tropopause, so that monsoon dynamics may be coherently diagnosed across modern and paleo observations and across idealized and comprehensive simulations. Accounting for zonal asymmetries in the circulation, land/ocean differences in surface fluxes, and the character of convective systems, such a monsoon framework would integrate our understanding at all relevant scales: from the fine details of how moisture and energy are lifted in the updrafts of thunderclouds, up to the global circulations

Rotating Stars in Relativity

Rotating relativistic stars have been studied extensively in recent years, both theoretically and observationally, because of the information one could obtain about the equation of state of matter at extremely high densities and because they are considered to be promising sources of gravitational waves. The latest theoretical understanding of rotating stars in relativity is reviewed in this updated article. The sections on the equilibrium properties and on the nonaxisymmetric instabilities in f-modes and r-modes have been updated and several new sections have been added on analytic solutions for the exterior spacetime, rotating stars in LMXBs, rotating strange stars, and on rotating stars in numerical relativity.Comment: 101 pages, 18 figures. The full online-readable version of this article, including several animations, will be published in Living Reviews in Relativity at http://www.livingreviews.org

Southern Hemisphere climate variability forced by Northern Hemisphere ice-sheet topography

The presence of large Northern Hemisphere ice sheets and reduced greenhouse gas concentrations during the Last Glacial Maximum fundamentally altered global ocean–atmosphere climate dynamics1. Model simulations and palaeoclimate records suggest that glacial boundary conditions affected the El Niño–Southern Oscillation2,3, a dominant source of short-term global climate variability. Yet little is known about changes in short-term climate variability at mid- to high latitudes. Here we use a high-resolution water isotope record from West Antarctica to demonstrate that interannual to decadal climate variability at high southern latitudes was almost twice as large at the Last Glacial Maximum as during the ensuing Holocene epoch (the past 11,700 years). Climate model simulations indicate that this increased variability reflects an increase in the teleconnection strength between the tropical Pacific and West Antarctica, owing to a shift in the mean location of tropical convection. This shift, in turn, can be attributed to the influence of topography and albedo of the North American ice sheets on atmospheric circulation. As the planet deglaciated, the largest and most abrupt decline in teleconnection strength occurred between approximately 16,000 years and 15,000 years ago, followed by a slower decline into the early Holocene

Termination 1 millennial‐scale rainfall avents over the Sunda Shelf

Recent paleoclimate reconstructions have suggested millennial-scale variability in the Indo-Pacific Warm Pool region coincident with events of the last deglaciation. Here we present a new stalagmite oxygen isotope record from northern Borneo, which today is located near the center of the region’s mean annual inter-tropical convergence zone. The record spans the full deglaciation, and reveals for the first time distinct oxygen isotope variations at this location connected with the Bølling-Allerød onset and the Younger Dryas event. The full deglaciation in the Borneo stalagmite proxy reconstruction appears remarkably similar to a 20-11 ka transient simulation of rainfall over the area produced using the isotope-enabled Community Earth System Model. In this model, periods of weakened Atlantic Ocean meridional overturning circulation are associated with an anomalous Western North Pacific anticyclone, which is produced in boreal autumn and shifts south over Borneo during boreal winter, causing dry conditions

Evidence of population differentiation in the dune grass Ammophila arenaria and its associated root-feeding nematodes

The interactions between herbivores and their host plants determine, to a great extent, the formation, structure and sustainability of terrestrial communities. The selection pressures that herbivores exert on plants and vice versa might vary geographically, leading eventually to population differentiation and local adaptation. In order to test whether there was reciprocal population differentiation among plants and belowground herbivores, we performed a cross-inoculation experiment using combinations of species and populations of root-feeders belonging to the genus Pratylenchus and the dune grass Ammophila arenaria from different geographic origins. Plant and herbivore responses in terms of growth and multiplication, respectively, were assessed at the end of the experiment. The 16 plant-herbivore combinations tested showed a high variation in the outcome of the interaction and revealed population differentiation in the responses of both, the host plant and the root-herbivores. The outcome in plant and herbivore performance was strongly case-dependent and for the sympatric combinations tested, support for local adaptation was not found. Nonetheless, the variation in plant-herbivore responses to experimental conditions highlights the plasticity of the interaction and may be pointing at spatial structuring in belowground plant-herbivore interactions