| Records |
| Author |
Haydar Karaoğlu, Barbara Romanowicz |
| Title |
Inferring global upper-mantle shear attenuation structure by waveform tomography using the spectral element method |
Type |
Journal |
| Year |
2018 |
Publication |
Geophysical Journal International |
Abbreviated Journal |
|
| Volume |
213 |
Issue |
3 |
Pages |
1536-1558 |
| Keywords |
|
| Abstract |
We present a global upper-mantle shear wave attenuation model that is built through a hybrid full-waveform inversion algorithm applied to long-period waveforms, using the spectral element method for wavefield computations. Our inversion strategy is based on an iterative approach that involves the inversion for successive updates in the attenuation parameter ($\delta Q^{-1}\mu$) and elastic parameters (isotropic velocity VS, and radial anisotropy parameter ξ) through a Gauss–Newton-type optimization scheme that employs envelope- and waveform-type misfit functionals for the two steps, respectively. We also include source and receiver terms in the inversion steps for attenuation structure. We conducted a total of eight iterations (six for attenuation and two for elastic structure), and one inversion for updates to source parameters. The starting model included the elastic part of the relatively high-resolution 3-D whole mantle seismic velocity model, SEMUCB-WM1, which served to account for elastic focusing effects. The data set is a subset of the three-component surface waveform data set, filtered between 400 and 60 s, that contributed to the construction of the whole-mantle tomographic model SEMUCB-WM1. We applied strict selection criteria to this data set for the attenuation iteration steps, and investigated the effect of attenuation crustal structure on the retrieved mantle attenuation structure. While a constant 1-D Qμ model with a constant value of 165 throughout the upper mantle was used as starting model for attenuation inversion, we were able to recover, in depth extent and strength, the high-attenuation zone present in the depth range 80–200 km. The final 3-D model, SEMUCB-UMQ, shows strong correlation with tectonic features down to 200–250 km depth, with low attenuation beneath the cratons, stable parts of continents and regions of old oceanic crust, and high attenuation along mid-ocean ridges and backarcs. Below 250 km, we observe strong attenuation in the southwestern Pacific and eastern Africa, while low attenuation zones fade beneath most of the cratons. The strong negative correlation of $Q^{-1}\mu$ and VS anomalies at shallow upper-mantle depths points to a common dominant origin for the two, likely due to variations in thermal structure. A comparison with two other global upper-mantle attenuation models shows promising consistency. As we updated the elastic 3-D model in alternate iterations, we found that the VS part of the model was stable, while the ξ structure evolution was more pronounced, indicating that it may be important to include 3-D attenuation effects when inverting for ξ, possibly due to the influence of dispersion corrections on this less well-constrained parameter. |
| Programme |
133 |
| Campaign |
|
| Address |
|
| Corporate Author |
|
Thesis |
Bachelor's thesis |
| Publisher |
|
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
0956-540X |
ISBN |
|
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
yes |
| Call Number |
|
Serial |
7325 |
| Permanent link to this record |
| |
|
| |
| Author |
Haydar Karaoğlu, Barbara Romanowicz |
| Title |
Global seismic attenuation imaging using full-waveform inversion: a comparative assessment of different choices of misfit functionals |
Type |
Journal |
| Year |
2018 |
Publication |
Geophysical Journal International |
Abbreviated Journal |
|
| Volume |
212 |
Issue |
2 |
Pages |
807-826 |
| Keywords |
|
| Abstract |
We present the results of synthetic tests that aim at evaluating the relative performance of three different definitions of misfit functionals in the context of 3-D imaging of shear wave attenuation in the earth’s upper mantle at the global scale, using long-period full-waveform data. The synthetic tests are conducted with simple hypothetical upper-mantle models that contain Qμ anomalies centred at different depths and locations, with or without additional seismic velocity anomalies. To build synthetic waveform data sets, we performed simulations of 50 events in the hypothetical (target) models, using the spectral element method, filtered in the period range 60–400 s. The selected events are chosen among 273 events used in the development of radially anisotropic model SEMUCB-WM1 and recorded at 495 stations worldwide. The synthetic Z-component waveforms correspond to paths and time intervals (fundamental mode and overtone Rayleigh waves) that exist in the real waveform data set. The inversions for shear attenuation structure are carried out using a Gauss–Newton optimization scheme in which the gradient and Hessian are computed using normal mode perturbation theory. The three different misfit functionals considered are based on time domain waveform (WF) and waveform envelope (E-WF) differences, as well as spectral amplitude ratios (SA), between observed and predicted waveforms. We evaluate the performance of the three misfit functional definitions in the presence of seismic noise and unresolved S-wave velocity heterogeneity and discuss the relative importance of physical dispersion effects due to 3-D Qμ structure. We observed that the performance of WF is poorer than the other two misfit functionals in recovering attenuation structure, unless anelastic dispersion effects are taken into account in the calculation of partial derivatives. WF also turns out to be more sensitive to seismic noise than E-WF and SA. Overall, SA performs best for attenuation imaging. Our tests show that it is important to account for 3-D elastic effects (focusing) before inverting for Qμ. Additionally, we show that including high signal-to-noise ratio overtone wave packets is necessary to resolve Qμ structure at depths greater than 250 km. |
| Programme |
133 |
| Campaign |
|
| Address |
|
| Corporate Author |
|
Thesis |
Bachelor's thesis |
| Publisher |
|
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
0956-540X |
ISBN |
|
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
yes |
| Call Number |
|
Serial |
7881 |
| Permanent link to this record |
| |
|
| |
| Author |
Hajo Eicken, Finn Danielsen, Josephine-Mary Sam, Maryann Fidel, Noor Johnson, Michael K Poulsen, Olivia A Lee, Katie V Spellman, Lisbeth Iversen, Peter Pulsifer, Martin Enghoff |
| Title |
Connecting Top-Down and Bottom-Up Approaches in Environmental Observing |
Type |
Journal |
| Year |
2021 |
Publication |
BioScience |
Abbreviated Journal |
|
| Volume |
71 |
Issue |
5 |
Pages |
467-483 |
| Keywords |
|
| Abstract |
Effective responses to rapid environmental change rely on observations to inform planning and decision-making. Reviewing literature from 124 programs across the globe and analyzing survey data for 30 Arctic community-based monitoring programs, we compare top-down, large-scale program driven approaches with bottom-up approaches initiated and steered at the community level. Connecting these two approaches and linking to Indigenous and local knowledge yields benefits including improved information products and enhanced observing program efficiency and sustainability. We identify core principles central to such improved links: matching observing program aims, scales, and ability to act on information; matching observing program and community priorities; fostering compatibility in observing methodology and data management; respect of Indigenous intellectual property rights and the implementation of free, prior, and informed consent; creating sufficient organizational support structures; and ensuring sustained community members’ commitment. Interventions to overcome challenges in adhering to these principles are discussed. |
| Programme |
1090,1206 |
| Campaign |
|
| Address |
|
| Corporate Author |
|
Thesis |
Bachelor's thesis |
| Publisher |
|
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
0006-3568 |
ISBN |
|
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
yes |
| Call Number |
|
Serial |
8249 |
| Permanent link to this record |
| |
|
| |
| Author |
Noor Johnson, Matthew L Druckenmiller, Finn Danielsen, Peter L Pulsifer |
| Title |
The Use of Digital Platforms for Community-Based Monitoring |
Type |
Journal |
| Year |
2021 |
Publication |
BioScience |
Abbreviated Journal |
|
| Volume |
71 |
Issue |
5 |
Pages |
452-466 |
| Keywords |
|
| Abstract |
Environmental observing programs that are based on Indigenous and local knowledge increasingly use digital technologies. Digital platforms may improve data management in community-based monitoring (CBM) programs, but little is known about how their use translates into tangible results. Drawing on published literature and a survey of 18 platforms, we examine why and how digital platforms are used in CBM programs and illuminate potential challenges and opportunities. Digital platforms make it easy to collect, archive, and share CBM data, facilitate data use, and support understanding larger-scale environmental patterns through interlinking with other platforms. Digital platforms, however, also introduce new challenges, with implications for the sustainability of CBM programs and communities’ abilities to maintain control of their own data. We expect that increased data access and strengthened technical capacity will create further demand within many communities for ethically developed platforms that aid in both local and larger-scale decision-making. |
| Programme |
1090,1206 |
| Campaign |
|
| Address |
|
| Corporate Author |
|
Thesis |
Bachelor's thesis |
| Publisher |
|
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
0006-3568 |
ISBN |
|
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
yes |
| Call Number |
|
Serial |
8248 |
| Permanent link to this record |
| |
|
| |
| Author |
Viblanc Vincent A, Valette Victorien, Kauffmann Marion, Malosse Nelly, Groscolas René, |
| Title |
Coping with social stress: heart rate responses to agonistic interactions in king penguins
|
Type |
Journal Article |
| Year |
2012 |
Publication |
Behavioral Ecology |
Abbreviated Journal |
|
| Volume |
23 |
Issue |
6 |
Pages |
1178 -1185 |
| Keywords |
|
| Abstract |
In colonial breeders, agonistic interactions between conspecifics are frequent and may have significant physiological implications. Physiological responses (e.g., increased heart rate) to such social stressors may be determined by the potential costs of agonistic interactions, such as personal injury or risk of breeding failure, and by the motivation of the individuals concerned. The latter may vary according to individuals reproductive status or willingness to engage in agonistic interactions. In this study, we investigated heart rate responses to aggressive interactions in a breeding colony of king penguins Aptenodytes patagonicus. From heart rate (HR) and behavior recorded in 20 adults at various stages of the breeding season, we investigated how king penguins reacted to aggressive neighbors. A total of 589 agonistic interactions, 223 in which birds were actors and 366 in which birds remained bystanders (i.e., witnesses that were not involved in interactions), were characterized. We found that HR increased during agonistic interactions, both in actors and bystanders. The intensity (threat displays or physical attacks), duration, and rate of aggressive events (number of threats/blows per unit time) of an interaction significantly influenced the HR response in actors. For bystanders, however, only the duration of interactions seemed to matter. Our results also suggest a role for individual motivation, as initiators of agonistic interactions displayed higher HR increases than responders, and as increases were not constant throughout the reproductive season. We conclude that individual risk assessment and motivation modulate physiological responses to social stressors in group-living animals.
|
| Programme |
119 |
| Campaign |
|
| Address |
|
| Corporate Author |
|
Thesis |
Bachelor's thesis |
| Publisher |
|
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
1045-2249 |
ISBN |
|
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
yes |
| Call Number |
|
Serial |
4174 |
| Permanent link to this record |
| |
|
| |
| Author |
Merkling Thomas, Leclaire Sarah, Danchin Etienne, Lhuillier Emeline, Wagner Richard H, White Joël, Hatch Scott A, Blanchard Pierrick, |
| Title |
Food availability and offspring sex in a monogamous seabird: insights from an experimental approach
|
Type |
Journal Article |
| Year |
2012 |
Publication |
Behavioral Ecology |
Abbreviated Journal |
|
| Volume |
23 |
Issue |
4 |
Pages |
751 -758 |
| Keywords |
|
| Abstract |
Sex allocation theory predicts that parents should favor offspring of the sex that provides the greatest fitness return. Despite growing evidence suggesting that vertebrates are able to overcome the constraint of chromosomal sex determination, the general pattern remains equivocal, indicating a need for experimental investigations. We used an experimental feeding design to study sex allocation during 3 years in black-legged kittiwakes (Rissa tridactyla). Intense malemale competition for securing a breeding site is common in this species in which males are heavier and larger than females. Hence, we hypothesized that parents producing fledglings in better than average condition, as supplementarily fed pairs do, would increase their fitness return by producing sons. Conversely, producing daughters would be a better tactic for Unfed parents. Hence, we predicted that Fed parents produce more sons than Unfed parents. This prediction is particularly expected if sexual dimorphism arises as early as during chick rearing, suggesting strong selective pressures for optimal male development. Our results showed that 1) males were heavier and larger than females prior to fledging and that 2) Fed parents produced relatively more male hatchlings than Unfed parents. We interpret this result in terms of a TriversWillard-type process. Furthermore, our data revealed that Unfed parents significantly overproduced female hatchlings, whereas offspring sex ratio was balanced among Fed parents. Because the 3 reproductive seasons we considered were particularly poor food years, Unfed parents may have overproduced daughters to avoid the apparent higher reproductive costs of raising sons.
|
| Programme |
1162 |
| Campaign |
|
| Address |
|
| Corporate Author |
|
Thesis |
Bachelor's thesis |
| Publisher |
|
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
1045-2249 |
ISBN |
|
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
yes |
| Call Number |
|
Serial |
4040 |
| Permanent link to this record |
| |
|
| |
| Author |
Leclaire Sarah, Bourret Vincent, Wagner Richard H, Hatch Scott A, Helfenstein Fabrice, Chastel Olivier, Danchin Étienne, |
| Title |
Behavioral and physiological responses to male handicap in chick-rearing black-legged kittiwakes
|
Type |
Journal Article |
| Year |
2011 |
Publication |
Behavioral Ecology |
Abbreviated Journal |
1045-2249 |
| Volume |
22 |
Issue |
6 |
Pages |
1156 -1165 |
| Keywords |
|
| Abstract |
Parental investment entails a trade-off between the benefits of effort in current offspring and the costs to future reproduction. Long-lived species are predicted to be reluctant to increase parental effort to avoid affecting their survival. We tested this hypothesis in black-legged kittiwakes Rissa tridactyla by clipping flight feathers of experimental males at the beginning of the chick-rearing period. We analyzed the consequences of this handicap on feeding and attendance behavior, body condition, integument coloration, and circulating levels of corticosterone and prolactin in handicapped males and their mates in comparison to unmanipulated controls. Chicks in both groups were compared in terms of aggressive behavior, growth, and mortality. Handicapped males lost more mass, had less bright integuments, and attended the nest less often than controls. Nevertheless, they fed their chicks at the same rate and had similar corticosterone and prolactin levels. Compared with control females, females mated with handicapped males showed a lower provisioning rate and higher nest attendance in the first days after manipulation. Their lower feeding rate probably triggered the increased sibling aggression and mortality observed in experimental broods. Our findings suggest that experimental females adaptively adjusted their effort to their mate's perceived quality or that their provisioning was constrained by their higher nest attendance. Overall, our results suggest that kittiwake males can decrease their condition for the sake of their chicks, which seems to contradict the hypothesis that kittiwakes should be reluctant to increase parental effort to avoid affecting their survival.
|
| Programme |
330;1162 |
| Campaign |
|
| Address |
|
| Corporate Author |
|
Thesis |
Bachelor's thesis |
| Publisher |
|
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
1045-2249 |
ISBN |
|
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
yes |
| Call Number |
|
Serial |
3243 |
| Permanent link to this record |
| |
|
| |
| Author |
Rochette, P.; Gattacceca, J.; Chevrier, V.; Mathé, P.E.; Menvielle, M. |
| Title |
Magnetism, Iron Minerals, and Life on Mars |
Type |
Journal Article |
| Year |
2006 |
Publication |
Astrobiology |
Abbreviated Journal |
Astrobiology |
| Volume |
6 |
Issue |
3 |
Pages |
423-436 |
| Keywords |
|
| Abstract |
|
| Programme |
412 |
| Campaign |
|
| Address |
|
| Corporate Author |
|
Thesis |
|
| Publisher |
Mary Ann Liebert, Inc., publishers |
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
1531-1074 |
ISBN |
|
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
yes |
| Call Number |
IPEV @ Thierry.Lemaire @ |
Serial |
5519 |
| Permanent link to this record |
| |
|
| |
| Author |
Richard Gerum, Sebastian Richter, Ben Fabry, Céline Le Bohec, Francesco Bonadonna, Anna Nesterova, Daniel P. Zitterbart |
| Title |
Structural organisation and dynamics in king penguin colonies |
Type |
Journal |
| Year |
2018 |
Publication |
Journal of Physics D: Applied Physics |
Abbreviated Journal |
|
| Volume |
51 |
Issue |
16 |
Pages |
164004 |
| Keywords |
|
| Abstract |
|
| Programme |
137,354 |
| Campaign |
|
| Address |
|
| Corporate Author |
|
Thesis |
Bachelor's thesis |
| Publisher |
|
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
0022-3727 |
ISBN |
0022-3727 |
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
yes |
| Call Number |
|
Serial |
7099 |
| Permanent link to this record |
| |
|
| |
| Author |
Sims, G., M. C. B. Ashley, X. Cui, J. R. Everett, L. Feng, X. Gong, S. Hengst, Z. Hu, C. Kulesa, J. S. Lawrence, D. M. Luong-Van, P. Ricaud, Z. Shang, J. W. V. Storey, L. Wang, H. Yang, J. Yang, X. Zhou, Z. Zhu |
| Title |
Precipitable Water Vapor above Dome A, Antarctica, Determined from Diffuse Optical Sky Spectra |
Type |
Journal Article |
| Year |
2012 |
Publication |
Publications of the Astronomical Society of the Pacific |
Abbreviated Journal |
|
| Volume |
124 |
Issue |
911 |
Pages |
74-83 |
| Keywords |
|
| Abstract |
The high altitudes and extremely low temperatures of the Antarctic plateau result in an exceedingly low atmospheric water vapor content. In this article we estimate the precipitable water vapor at Dome A using optical spectra of the diffuse solar irradiance in the zenith direction. The spectra were obtained from the Nigel spectrometer at Dome A during 2009. We find that the Nigel spectra contain sufficient information to extract daily average water vapor estimates, which agree with satellite observations to within ± 0.22 mm . Finally, we use these water vapor estimates to model the optical and near-IR transmission (between 700 nm and 2.5 μm) of Dome A to demonstrate significant advantages gained in this wavelength range and compare it with that of Paranal and Chajnantor, two midlatitude observatories. |
| Programme |
910 |
| Campaign |
|
| Address |
|
| Corporate Author |
|
Thesis |
Bachelor's thesis |
| Publisher |
|
Place of Publication |
|
Editor |
|
| Language |
|
Summary Language |
|
Original Title |
|
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
0004-6280 |
ISBN |
|
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
yes |
| Call Number |
|
Serial |
3632 |
| Permanent link to this record |
