| 1. |
- Harcourt, R., et al.
(författare)
-
Animal-borne telemetry: An integral component of the ocean observing toolkit
- 2019
-
Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 6:JUN
-
Tidskriftsartikel (refereegranskat)abstract
- Animal telemetry is a powerful tool for observing marine animals and the physical environments that they inhabit, from coastal and continental shelf ecosystems to polar seas and open oceans. Satellite-linked biologgers and networks of acoustic receivers allow animals to be reliably monitored over scales of tens of meters to thousands of kilometers, giving insight into their habitat use, home range size, the phenology of migratory patterns and the biotic and abiotic factors that drive their distributions. Furthermore, physical environmental variables can be collected using animals as autonomous sampling platforms, increasing spatial and temporal coverage of global oceanographic observation systems. The use of animal telemetry, therefore, has the capacity to provide measures from a suite of essential ocean variables (EOVs) for improved monitoring of Earth's oceans. Here we outline the design features of animal telemetry systems, describe current applications and their benefits and challenges, and discuss future directions. We describe new analytical techniques that improve our ability to not only quantify animal movements but to also provide a powerful framework for comparative studies across taxa. We discuss the application of animal telemetry and its capacity to collect biotic and abiotic data, how the data collected can be incorporated into ocean observing systems, and the role these data can play in improved ocean management. © 2019 Harcourt, Sequeira, Zhang, Roquet, Komatsu, Heupel, McMahon, Whoriskey, Meekan, Carroll, Brodie, Simpfendorfer, Hindell, Jonsen, Costa, Block, Muelbert, Woodward, Weise, Aarestrup, Biuw, Boehme, Bograd, Cazau, Charrassin, Cooke, Cowley, de Bruyn, Jeanniard du Dot, Duarte, Eguíluz, Ferreira, Fernández-Gracia, Goetz, Goto, Guinet, Hammill, Hays, Hazen, Hückstädt, Huveneers, Iverson, Jaaman, Kittiwattanawong, Kovacs, Lydersen, Moltmann, Naruoka, Phillips, Picard, Queiroz, Reverdin, Sato, Sims, Thorstad, Thums, Treasure, Trites, Williams, Yonehara and Fedak.
|
|
| 2. |
- Iverson, N. R., et al.
(författare)
-
A Theoretical Model of Drumlin Formation Based on Observations at Múlajökull, Iceland
- 2017
-
Ingår i: Journal of Geophysical Research - Earth Surface. - 0148-0227 .- 2156-2202. ; 122:12, s. 2302-2323
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract The drumlin field at the surge-type glacier, Múlajökull, provides an unusual opportunity to build a model of drumlin formation based on field observations in a modern drumlin-forming environment. These observations indicate that surges deposit till layers that drape the glacier forefield, conform to drumlin surfaces, and are deposited in shear. Observations also indicate that erosion helps create drumlin relief, effective stresses in subglacial till are highest between drumlins, and during quiescent flow, crevasses on the glacier surface overlie drumlins while subglacial channels occupy intervening swales. In the model, we consider gentle undulations on the bed bounded by subglacial channels at low water pressure. During quiescent flow, slip of temperate ice across these undulations and basal water flow toward bounding channels create an effective stress distribution that maximizes till entrainment in ice on the heads and flanks of drumlins. Crevasses amplify this effect but are not necessary for it. During surges, effective stresses are uniformly low, and the bed shears pervasively. Vigorous basal melting during surges releases debris from ice and deposits it on the bed, with deposition augmented by transport in the deforming bed. As surge cycles progress, drumlins migrate downglacier and grow at increasing rates, due to positive feedbacks that depend on drumlin height. Drumlin growth can be accompanied by either net aggradation or erosion of the bed, and drumlin heights and stratigraphy generally correspond with observations. This model highlights that drumlin growth can reflect instabilities other than those of bed shear instability models, which require heuristic till transport assumptions.
|
|
| 3. |
- McCracken, R. G., et al.
(författare)
-
Origin of the active drumlin field at Mulajokull, Iceland: New insights from till shear and consolidation patterns
- 2016
-
Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 148, s. 243-260
-
Tidskriftsartikel (refereegranskat)abstract
- Stratigraphic and morphologic data previously collected from the forefleld of Millajokull, Iceland, suggest that its recent surge cycles are responsible for the formation of drumlins there and that their relief reflects both deposition on drumlins and erosion between them. We have tested these ideas and aspects of leading models of drumlin formation by studying past patterns of bed deformation and effective stress in basal tills of the glacier's forefield. Patterns of till strain indicated by the anisotropy of magnetic susceptibility (AMS) of similar to 2300 intact till samples indicate that till was deposited during shear deformation, with shearing azimuths and planes that conform to the drumlin morphology. Thus, till deposition occurred as drumlins grew, in agreement with LiDAR data indicating that the degree of aggradation of the glacier forefleld is largest in areas subjected to the most surges. Previously described unconformities on the drumlin flanks, however, indicate that drumlin relief at Mulajokull has resulted, in part, from erosion. Given that the last surge deposited a till layer both on and between drumlins, a reasonable hypothesis is that erosion between drumlins occurred during normal (quiescent) flow of the glacier between surges. Densities of till samples, analyzed in conjunction with laboratory consolidation tests, indicate that effective stresses on the bed during such periods were on the order of 100 kPa larger between drumlins than within them, an observation consistent with subglacial channels at low water pressure occupying interdrumlin areas. Transport of sediment by turbulent flow in these channels or high effective stress adjacent to them causing enhanced till entrainment in ice or increased depths of bed deformation would promote the sediment flux divergence necessary to erode areas between drumlins. The observation that effective stresses were higher between drumlins than within them is the opposite of that presumed in leading models of drumlin formation. Moreover, the lack of AMS-fabric evidence of longitudinal compression in drumlin tills does not support some models of drumlin formation that invoke negative till-flux gradients in a deforming bed.
|
|
