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1. Detecting climate signals in populations across life histories. Global Change Biology

   https://doi.org/DOI: 10.1111/gcb.16041  

   Jenouvrier S., Long M. (April 2022, Global change biology)

   Editorial Board, Editor; Executive Editor, Rachel Shekar; Assistant Editor, Rhea Bruno; Co-Founding Editor Harry Smith FRS, University of; Reviews Editor Danielle Way, Australian National (Ed.)

   Climate impacts are not always easily discerned in wild populations as detecting climate change signals in populations is challenged by stochastic noise associated with natural climate variability, variability in biotic and abiotic processes, and observation error in demographic rates. Detection of the impact of climate change on populations requires making a formal distinction between signals in the population associated with long-term climate trends from those generated by stochastic noise. The time of emergence (ToE) identifies when the signal of anthropogenic climate change can be quantitatively distinguished from natural climate variability. This concept has been applied extensively in the climate sciences, but has not been explored in the context of population dynamics. Here, we outline an approach to detecting climate-driven signals in populations based on an assessment of when climate change drives population dynamics beyond the envelope characteristic of stochastic variations in an unperturbed state. Specifically, we present a theoretical assessment of the time of emergence of climate-driven signals in population dynamics (urn:x-wiley:13541013:media:gcb16041:gcb16041-math-0001). We identify the dependence of urn:x-wiley:13541013:media:gcb16041:gcb16041-math-0002 on the magnitude of both trends and variability in climate and also explore the effect of intrinsic demographic controls on urn:x-wiley:13541013:media:gcb16041:gcb16041-math-0003. We demonstrate that different life histories (fast species vs. slow species), demographic processes (survival, reproduction), and the relationships between climate and demographic rates yield population dynamics that filter climate trends and variability differently. We illustrate empirically how to detect the point in time when anthropogenic signals in populations emerge from stochastic noise for a species threatened by climate change: the emperor penguin. Finally, we propose six testable hypotheses and a road map for future research. 

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2. Climatic Asynchrony and Hydrologic Inefficiency Explain the Global Pattern of Water Availability

   https://doi.org/10.1029/2022GL101214  

   Jawitz, James W.; Klammler, Harald; Reaver, Nathan G. F. (December 2022, Geophysical Research Letters)

   Abstract The mechanisms underlying observed global patterns of partitioning precipitation () to evapotranspiration () and runoff () are controversially debated. We test the hypothesis that asynchrony between climatic water supply and demand is sufficient to explain spatio‐temporal variability of water availability. We developed a simple analytical model forthat is determined by four dimensionless characteristics of intra‐annual water supply and demand asynchrony. The analytical model, populated with gridded climate data, accurately predicted global runoff patterns within 2%–4% of independent estimates from global climate models, with spatial patterns closely correlated to observations (). The supply‐demand asynchrony hypothesis provides a physically based explanation for variability of water availability using easily measurable characteristics of climate. The model revealed widespread responsiveness of water budgets to changes in climate asynchrony in almost every global region. Furthermore, the analytical model using global averages independently reproduced the Budyko curve () providing theoretical foundation for this widely used empirical relationship. 

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3. Embedding hypertrees into steiner triple systems

   https://doi.org/10.1002/jcd.21641  

   Elliott, Bradley; Rödl, Vojtěch (November 2018, Journal of Combinatorial Designs)

   Abstract In this paper, we are interested in the following question: given an arbitrary Steiner triple systemonvertices and any 3‐uniform hypertreeonvertices, is it necessary thatcontainsas a subgraph provided? We show the answer is positive for a class of hypertrees and conjecture that the answer is always positive. 

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4. Climatic Drivers of Deglacial SST Variability in the Eastern Pacific

   https://doi.org/10.1029/2021PA004264  

   Meegan Kumar, Dervla; Tierney, Jessica E.; Bhattacharya, Tripti; Zhu, Jiang; McCarty, Logan; Murray, James W. (October 2021, Paleoceanography and Paleoclimatology)

   Abstract We explore the response of northeastern Pacific sea surface temperature (SST) to deglacial (16–7 ka) climate variability as recorded in‐based SST reconstructions spanning 65°N to 10°S. Included in the analysis is a new 23 kyr SST record from core NH8P from the northwest Mexican Margin. We isolate spatiotemporal patterns in regional SSTs with trend empirical orthogonal function (TEOF) analysis. The dominant TEOF mode reflects deglacial warming associated with rising. Tropical and subtropical SSTs correlated most strongly with this mode, suggesting that the thermodynamic response of the tropical eastern Pacific to greenhouse gas forcing was the dominant driver of regional SST change during deglaciation. The second TEOF mode reflects millennial‐scale variability and is most strongly expressed in subpolar SSTs. The synchronous timing between North Pacific and North Atlantic SST oscillations is evidence for the rapid transmission of millennial‐scale climate perturbations between the basins, likely through an atmospheric teleconnection. SSTs at NH8P have no correlation with either leading TEOF mode as there is minimal change in SST at this site after20 ka. A model simulation of the LGM indicates that glacial cooling was muted in much of the Eastern Pacific Warm Pool (EPWP), in which NH8P lies, due to reductions in latent heat flux. This suggests that the wind‐evaporation‐SST feedback was responsible for the attenuation of EPWP cooling. Overall, this study highlights the distinct latitudinal trends in the Pacific's response to deglaciation. 

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5. Decreased Stratification in the Abyssal Southwest Pacific Basin and Implications for the Energy Budget

   https://doi.org/10.1029/2021GL094322  

   Zhang, Helen J.; Whalen, Caitlin B.; Kumar, Nirnimesh; Purkey, Sarah G. (September 2021, Geophysical Research Letters)

   Abstract As the abyssal oceans warm, stratification is also expected to change in response. This change may impact mixing and vertical transport by altering the buoyancy flux, internal wave generation, and turbulent dissipation. In this study, repeated surveys of three hydrographic sections in the Southwest Pacific Basin between the 1990s and 2010s are used to estimate the change in buoyancy frequency. We find that below the°C isotherm,is on average reduced by a scaling factor of, a 12% reduction, per decade that intensifies with depth. At°C, we observe the biggest change:, or a 29% reduction per decade. Within the same period, the magnitude of vertical diffusive heat flux is also reduced by about, although this estimate is sensitive to the choice of estimated diffusivity. Finally, implications of these results for the heat budget and global ocean circulation are qualitatively discussed. 

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