Climate warming, water storage, and Chinook salmon in California’s Sacramento Valley

The Chinook salmon (Oncorhynchus tshawytscha) spawns and rears in the cold, freshwater rivers and tributaries of California’s Central Valley, with four separate seasonal runs including fall and late-fall runs, a winter run, and a spring run. Dams and reservoirs have blocked access to most of the Chinook’s ancestral spawning areas in the upper reaches and tributaries. Consequently, the fish rely on the mainstem of the Sacramento River for spawning habitat. Future climatic warming could lead to alterations of the river’s temperature regime, which could further reduce the already fragmented Chinook habitat. Specifically, increased water temperatures could result in spawning and rearing temperature exceedences, thereby jeopardizing productivity, particularly in drought years. Paradoxically, water management plays a key role in potential adaptation options by maintaining spawning and rearing habitat now and in the future, as reservoirs such as Shasta provide a cold water supply that will be increasingly needed to counter the effects of climate change. Results suggest that the available cold pool behind Shasta could be maintained throughout the summer assuming median projections of mid-21st century warming of 2°C, but the maintenance of the cold pool with warming on the order of 4°C could be very challenging. The winter and spring runs are shown to be most at risk because of the timing of their reproduction.     

The Catalan seismic crisis (1427 and 1428; NE Iberian Peninsula): Geological sources and earthquake triggering

The Catalan seismic crisis of the years 1427 and 1428 is one of the most destructive seismic episodes that happened in the northeastern Iberian Peninsula in historical times. The main earthquakes of this crisis occurred on March 19th 1427 in the zone around Amer (I_EMS-98 = VIII), May 15th 1427 in the vicinity of Olot (I_EMS-98 = VIII) and on February 2nd 1428 in the area close to Camprodon (I_EMS-98 = IX). There is much evidence that the Amer fault produced the first two events of this crisis, but is still uncertain which fault generated the earthquake on February 2nd 1428. Using newly available macroseismic data, the earthquake area sources of the three main earthquakes of the crisis have been obtained and they corroborate that the Amer fault may be the origin of the first two events. However, the area source corresponding to the last earthquake of the crisis cannot be associated to a single fault and indicates three possible candidates: the Vallfogona and Ribes-Camprodon thrusts and the Amer normal fault. Modeling of the Coulomb failure stress transfer has been performed to help determine the best candidate responsible for the February event. The results of the modeling points to: (a) a triggering relationship between the three main events of the crisis and (b) the Amer fault, or a similar extensional fault close and parallel to it, as the most probable origin of the earthquake on February 2nd 1428.     

Coherence between atmospheric teleconnections,Great Lakes water levels,and regional climate

We investigated the frequency domain relationships between four atmospheric teleconnections (Trans-Niño Index TNI, Pacific Decadal Oscillation PDO, Northern Annular Mode/Arctic Oscillation Index NAM/AO, and Pacific/North American PNA pattern) and water levels in the Great Lakes from 1948 to 2002 by quantifying the coherence between these time series. The levels in all Great Lakes are significantly correlated with the TNI in the frequency range (3–7)⁻¹ cycles year⁻¹, and with the PDO in interdecadal frequencies. The levels in Lakes Superior, Michigan, and Erie are significantly correlated with the PNA pattern in interdecadal frequencies, and the levels in all Great Lakes are significantly correlated with the NAM/AO in interannual frequencies.     

Climate change and population history in the Pacific Lowlands of Southern Mesoamerica

Core MAN015 from Pacific coastal Guatemala contains sediments accumulated in a mangrove setting over the past 6500 yr. Chemical, pollen, and phytolith data, which indicate conditions of estuarine deposition and terrigenous inputs from adjacent dry land, document Holocene climate variability that parallels the Maya lowlands and other New World tropical locations. Human population history in this region may be driven partly by climate variation: sedentary human populations spread rapidly through the estuarine zone of the lower coast during a dry and variable 4th millennium B.P. Population growth and cultural florescence during a long, relatively moist period (2800–1200 B.P.) ended around 1200 B.P., a drying event that coincided with the Classic Maya collapse.     

Africa and the global carbon cycle

The African continent has a large and growing role in the global carbon cycle, with potentially important climate change implications. However, the sparse observation network in and around the African continent means that Africa is one of the weakest links in our understanding of the global carbon cycle. Here, we combine data from regional and global inventories as well as forward and inverse model analyses to appraise what is known about Africa's continental-scale carbon dynamics. With low fossil emissions and productivity that largely compensates respiration, land conversion is Africa's primary net carbon release, much of it through burning of forests. Savanna fire emissions, though large, represent a short-term source that is offset by ensuing regrowth. While current data suggest a near zero decadal-scale carbon balance, interannual climate fluctuations (especially drought) induce sizeable variability in net ecosystem productivity and savanna fire emissions such that Africa is a major source of interannual variability in global atmospheric CO₂. Considering the continent's sizeable carbon stocks, their seemingly high vulnerability to anticipated climate and land use change, as well as growing populations and industrialization, Africa's carbon emissions and their interannual variability are likely to undergo substantial increases through the 21st century.     

Kilometer-wave type III burst: Harmonic emission revealed by direction and time of arrival

A type III solar burst was observed at seven frequencies between 3.5 MHz and 80 kHz by the Michigan experiment aboard the IMP-6 satellite. From the data we can determine burst direction-of-arrival as well as time-of-arrival. We predict these quantities using simple models whose parameters we vary to obtain a good fit to the observations. We find that between 3.5 MHz and 230 kHz the observed radiation was emitted at the fundamental of the local plasma frequency while below 230 kHz it was emitted at the second harmonic. The exciter particles that produced the burst onset and burst peak have velocities of 0.27 and 0.12, respectively, in units of the velocity of light.     

Meat consumption and climate change: the role of non-governmental organizations

The contribution of livestock production to climate change is now widely acknowledged. Despite this, efforts to reduce meat consumption in light of climate change have been relatively limited. One potential avenue for encouraging consumption changes is via non-governmental organizations (NGOs). This study used a qualitative approach to understand how and to what extent environmental, food-focused, and animal protection NGOs in the U.S., Canada, and Sweden have worked to reduce or alter domestic meat consumption in light of climate change. While almost all of the NGOs examined had mentioned the issue on their websites, few had established formal campaigns to reduce meat consumption. Active public outreach was dominated by animal protection and food-focused groups, particularly in the U.S. and Canada. Animal protection organizations advocated for larger reductions in meat consumption than environmental groups. Few NGOs sought to promote national-level polices to reduce meat consumption. There is a continued need for public education campaigns with clear messages, particularly by environmental NGOs, as well as efforts to build support for policy measures that seek to reduce meat consumption.     

VLA observations of hot spots in high luminosity radio sources

VLA observations at 6 cm have been made of 16 distant luminous 3C sources that appeared to be unresolved or slightly resolved in Cambridge maps but which were known from VLBI observations to contain significant fine structure on the scale of about 1 kpc in their lobes. The general morphology of these sources is very similar to that of their nearby powerful counterparts; most of the lobes contain low brightness tails which are often directed from the hot spots towards the associated optical object. The hot spots are generally unresolved by the VLA observations; in 3C 254, 3C 268.4 and 3C 352, one of the lobes contains two hot spots.     

Reduced-order modeling for thermal recovery processes

Thermal recovery can entail considerably higher costs than conventional oil recovery, so the use of computational optimization techniques in designing and operating these processes may be beneficial. Optimization, however, requires many simulations, which results in substantial computational cost. Here, we implement a model-order reduction technique that aims at large reductions in computational requirements. The technique considered, trajectory piecewise linearization (TPWL), entails the representation of new solutions in terms of linearizations around previously simulated (and saved) training solutions. The linearized representation is projected into a low-dimensional space, with the projection matrix constructed through proper orthogonal decomposition of solution “snapshots” generated in the training step. Two idealized problems are considered here: primary production of oil driven by downhole heaters and a simplified model for steam-assisted gravity drainage, where water and steam are treated as a single “effective” phase. The strong temperature dependence of oil viscosity is included in both cases. TPWL results for these systems demonstrate that the method can provide accurate predictions relative to full-order reference solutions. Observed runtime speedups are very substantial, over 2 orders of magnitude for the cases considered. The overhead associated with TPWL model construction is equivalent to the computation time for several full-order simulations (the precise overhead depends on the number of training runs), so the method is only applicable if many simulations are to be performed.