The comparative breeding ecology of sympatric common and arctic terns in N.E. England

The life-history traits of two sympatric seabird species, the Common Sterna hirundo and Arctic Tern S. paradisaea, and the flexibility of these traits in relation to short and longer term changes in environmental conditions were measured at Coquet Island, N.E. England. The study focused primarily on inter and intraspecific differences in annual productivity and chick growth, adult time budgets and provisioning rates, and the relationships between these different aspects of reproductive performance. Of the two species, Common Terns delivered larger food items, delivered food at a higher rate to the nest and attended the nest more frequently, indicating that they made trips of shorter average duration. Daily metabolizable energy intake of chicks was about 30% higher in Common Terns than in Arctic Terns, yet the size-specific growth rates of the two species were almost identical, indicating a major difference between species in nestling energy budgets. Brooding appeared to play a less important role in the energy budgets of Common Terns, and the number of chicks that Arctic Terns could raise was probably limited not only by the rate at which parents could supply food to the nest but also by the requirements of chicks for brooding. Increased brood size, low annual food abundance and extreme weather conditions had a negative effect on chick mass development in both tern species. Flexibility of mass growth rates in Arctic and Common Terns may act as a fine-tuning mechanism to regulate provisioning in these species. By maintaining structural growth rates, final fledging mass and final fledging size of nestlings at the expense of retarded mass development rates, these species seem to be able to maximize annual reproductive output and possibly, for parents and nestlings, future survival. Predation of eggs and chicks was generally infrequent and affected mostly very young nestlings. However, Black-headed Gulls took many tern eggs in a year when inshore food supplies were particularly low

Challenges and research priorities to understand interactions between climate, ice sheets and global mean sea level during past interglacials

© 2019 Elsevier Ltd. This paper is an outcome of the joint workshop organized by the PAGES-INQUA PALSEA (PALeo constraints on SEA level rise) and the PAGES-PMIP QUIGS (QUaternary InterGlacialS) Working Groups in Galloway NJ (USA), 27–30 September 2018. We are very grateful to all the participants for the stimulating discussions that contributed to this article. We also thank Past Global Changes (PAGES), the International Union for Quaternary Research (INQUA), the United States National Science Foundation and Rutgers University, Institute of Earth, Ocean, and Atmospheric Sciences for their financial support. E.C. acknowledges financial support from the ChronoClimate project, funded by the Carlsberg Foundation. B.O.B acknowledges support by the National Center for Atmospheric Research, which is a major facility sponsored by the United States National Science Foundation under Cooperative Agreement No. 1852977, and additionally by the U.S. DOE (DE-SC0012606).Quaternary interglacials provide key observations of the Earth system's responses to orbital and greenhouse gas forcing. They also inform on the capabilities of Earth system models, used for projecting the polar ice-sheet and sea-level responses to a regional warmth comparable to that expected by 2100 C.E. However, a number of uncertainties remain regarding the processes and feedbacks linking climate, ice-sheet and sea-level changes during past warm intervals. Here, we delineate the major research questions that need to be resolved and future research directions that should be taken by the paleoclimate, sea-level and ice-sheet research communities in order to increase confidence in the use of past interglacial climate, ice-sheet and sea-level reconstructions to constrain future predictions. These questions were formulated during a joint workshop held by the PAGES-INQUA PALSEA (PALeo constraints on SEA level rise) and the PAGES-PMIP QUIGS (QUaternary InterGlacialS) Working Groups in September 2018.Past Global Changes (PAGES)International Union for Quaternary Research (INQUA)United States National Science FoundationRutgers UniversityInstitute of Earth, Ocean, and Atmospheric SciencesCarlsberg FoundationNational Center for Atmospheric ResearchU.S. DOEDepto. de Física de la Tierra y AstrofísicaFac. de Ciencias FísicasTRUEpu

On the Assouad dimension of self-similar sets with overlaps

It is known that, unlike the Hausdorff dimension, the Assouad dimension of a self-similar set can exceed the similarity dimension if there are overlaps in the construction. Our main result is the following precise dichotomy for self-similar sets in the line: either the \emph{weak separation property} is satisfied, in which case the Hausdorff and Assouad dimensions coincide; or the \emph{weak separation property} is not satisfied, in which case the Assouad dimension is maximal (equal to one). In the first case we prove that the self-similar set is Ahlfors regular, and in the second case we use the fact that if the \emph{weak separation property} is not satisfied, one can approximate the identity arbitrarily well in the group generated by the similarity mappings, and this allows us to build a \emph{weak tangent} that contains an interval. We also obtain results in higher dimensions and provide illustrative examples showing that the `equality/maximal' dichotomy does not extend to this setting.Comment: 24 pages, 2 figure

SEMIC: an efficient surface energy and mass balance model applied to the Greenland ice sheet

We present SEMIC, a Surface Energy and Mass balance model of Intermediate Complexity for snow-and ice-covered surfaces such as the Greenland ice sheet. SEMIC is fast enough for glacial cycle applications, making it a suitable replacement for simpler methods such as the positive degree day (PDD) method often used in ice sheet modelling. Our model explicitly calculates the main processes involved in the surface energy and mass balance, while maintaining a simple interface and requiring minimal data input to drive it. In this novel approach, we parameterise diurnal temperature variations in order to more realistically capture the daily thaw-freeze cycles that characterise the ice sheet mass balance. We show how to derive optimal model parameters for SEMIC specifically to reproduce surface characteristics and day-to-day variations similar to the regional climate model MAR (Modele Atmospherique Regional, version 2) and its incorporated multilayer snowpack model SISVAT (Soil Ice Snow Vegetation Atmosphere Transfer). A validation test shows that SEMIC simulates future changes in surface temperature and surface mass balance in good agreement with the more sophisticated multilayer snowpack model SISVAT included in MAR. With this paper, we present a physically based surface model to the ice sheet modelling community that is general enough to be used with in situ observations, climate model, or reanalysis data, and that is at the same time computationally fast enough for long-term integrations, such as glacial cycles or future climate change scenarios

Analysing trade-offs and synergies between SDGs for urban development, food security and poverty alleviation in rapidly changing peri-urban areas: a tool to support inclusive urban planning

Transitional peri-urban contexts are frontiers for sustainable development where land-use change involves negotiation and contestation between diverse interest groups. Multiple, complex trade-offs between outcomes emerge which have both negative and positive impacts on progress towards achieving Sustainable Development Goals (SDGs). These trade-offs are often overlooked in policy and planning processes which depend on top-down expert perspectives and rely on course grain aggregate data which does not reflect complex peri-urban dynamics or the rapid pace of change. Tools are required to address this gap, integrate data from diverse perspectives and inform more inclusive planning processes. In this paper, we draw on a reinterpretation of empirical data concerned with land-use change and multiple dimensions of food security from the city of Wuhan in China to illustrate some of the complex trade-offs between SDG goals that tend to be overlooked with current planning approaches. We then describe the development of an interactive web-based tool that implements deep learning methods for fine-grained land-use classification of high-resolution remote sensing imagery and integrates this with a flexible method for rapid trade-off analysis of land-use change scenarios. The development and potential use of the tool are illustrated using data from the Wuhan case study example. This tool has the potential to support participatory planning processes by providing a platform for multiple stakeholders to explore the implications of planning decisions and land-use policies. Used alongside other planning, engagement and ecosystem service mapping tools it can help to reveal invisible trade-offs and foreground the perspectives of diverse stakeholders. This is vital for building approaches which recognise how trade-offs between the achievement of SDGs can be influenced by development interventions

Climatic risks and impacts in South Asia: extremes of water scarcity and excess

This paper reviews the current knowledge of climatic risks and impacts in South Asia associated with anthropogenic warming levels of 1.5-4 A degrees C above pre-industrial values in the twenty-first century. It is based on the World Bank Report "Turn Down the Heat, Climate Extremes, Regional Impacts and the Case for Resilience" (2013b) . Many of the climate change impacts in the region, which appear quite severe even with relatively modest warming of 1.5-2 A degrees C, pose significant hazards to development. For example, increased monsoon variability and loss or glacial meltwater will likely confront populations with ongoing and multiple challenges. The result is a significant risk to stable and reliable water resources for the region, with increases in peak flows potentially causing floods and dry season flow reductions threatening agriculture. Irrespective of the anticipated economic development and growth, climate projections indicate that large parts of South Asia's growing population and especially the poor are likely to remain highly vulnerable to climate change

MIS-11 duration key to disappearance of the Greenland ice sheet

Palaeo data suggest that Greenland must have been largely ice free during Marine Isotope Stage 11 (MIS-11). However, regional summer insolation anomalies were modest during this time compared to MIS-5e, when the Greenland ice sheet likely lost less volume. Thus it remains unclear how such conditions led to an almost complete disappearance of the ice sheet. Here we use transient climate-ice sheet simulations to simultaneously constrain estimates of regional temperature anomalies and Greenland's contribution to the MIS-11 sea-level highstand. We find that Greenland contributed 6.1m (3.9-7.0 m, 95% credible interval) to sea level, similar to 7 kyr after the peak in regional summer temperature anomalies of 2.8 degrees C (2.1-3.4 degrees C). The moderate warming produced a mean rate of mass loss in sea-level equivalent of only around 0.4m per kyr, which means the long duration of MIS-11 interglacial conditions around Greenland was a necessary condition for the ice sheet to disappear almost completely

The sensitivity of the Greenland Ice Sheet to glacial-interglacial oceanic forcing

Observations suggest that during the last decades the Greenland Ice Sheet (GrIS) has experienced a gradually accelerating mass loss, in part due to the observed speed-up of several of Greenland's marine-terminating glaciers. Recent studies directly attribute this to warming North Atlantic temperatures, which have triggered melting of the outlet glaciers of the GrIS, grounding-line retreat and enhanced ice discharge into the ocean, contributing to an acceleration of sea-level rise. Reconstructions suggest that the influence of the ocean has been of primary importance in the past as well. This was the case not only in interglacial periods, when warmer climates led to a rapid retreat of the GrIS to land above sea level, but also in glacial periods, when the GrIS expanded as far as the continental shelf break and was thus more directly exposed to oceanic changes. However, the GrIS response to palaeo-oceanic variations has yet to be investigated in detail from a mechanistic modelling perspective. In this work, the evolution of the GrIS over the past two glacial cycles is studied using a three-dimensional hybrid ice-sheet-shelf model. We assess the effect of the variation of oceanic temperatures on the GrIS evolution on glacial-interglacial timescales through changes in submarine melting. The results show a very high sensitivity of the GrIS to changing oceanic conditions. Oceanic forcing is found to be a primary driver of GrIS expansion in glacial times and of retreat in interglacial periods. If switched off, palaeo-atmospheric variations alone are not able to yield a reliable glacial configuration of the GrIS. This work therefore suggests that considering the ocean as an active forcing should become standard practice in palaeo-ice-sheet modelling

Shape coexistence in the neutron-deficient even-even Hg^(182-188) isotopes studied via Coulomb excitation

Coulomb-excitation experiments to study electromagnetic properties of radioactive even-even Hg isotopes were performed with 2.85 MeV=nucleon mercury beams from REX-ISOLDE. Magnitudes and relative signs of the reduced E2 matrix elements that couple the ground state and low-lying excited states in ^(182−188)Hg were extracted. Information on the deformation of the ground and the first excited 0þ states was deduced using the quadrupole sum rules approach. Results show that the ground state is slightly deformed and of oblate nature, while a larger deformation for the excited 0þ state was noted in ^(182;184)Hg. The results are compared to beyond mean field and interacting-boson based models and interpreted within a two-state mixing model. Partial agreement with the model calculations was obtained. The presence of two different structures in the light even-mass mercury isotopes that coexist at low excitation energy is firmly established