Hoover R.R.,Center for Quantitative Fisheries Ecology |
Jones C.M.,Center for Quantitative Fisheries Ecology |
Grosch C.E.,Center for Coastal Physical Oceanography
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2012
The ability to accurately measure the timing of migration is fundamental in testing hypotheses in marine ecology that deal with migration and movement of fish populations. Timing and patterns of movement in larval and juvenile fish have been estimated using life history scans of the chemical signatures encoded in their otoliths. We provide a quantitative approach to analyzing life history scan data using spectral analysis, which retrospectively measures the timing of ingress for individual fish. Saggital otoliths from juvenile Atlantic croaker (Micropogonias undulatus) were sampled using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Spectral analyses on these data estimate the timing of ingress at 68 days on average using strontium and 85 days using barium. Based on the inflection points of their nonlinear mixing curves, these data reveal entry and subsequent movement up-estuary. Moreover, we use these spectrally derived estimates to show that growth rates did not drive ingress timing for our samples. These data thus lend no support to the critical-size hypothesis in this instance.
MacK S.,Center for Coastal Physical Oceanography |
Padman L.,Earth and Space Research |
Klinck J.,Center for Coastal Physical Oceanography
Geophysical Research Letters | Year: 2013
The periodic divergence of stress applied by ocean tidal currents to sea ice affects the time-averaged ice concentration (Cice) and heat and freshwater fluxes at the ocean surface. We demonstrate that, at sufficiently high latitudes, tidal variability in Cice can be extracted from single-swath data from the Advanced Microwave Scanning Radiometer-EOS (AMSR-E) satellite passive microwave sensor, although time intervals between swaths are irregular. For the northwest Ross Sea where tidal currents are large, tidal divergence is the dominant cause of Cice variability in winter, with a range of ±0.2 about a mean of ~0.8. Daily-averaged Cice values vary from >0.9 at neap tides to ~0.7 at spring tides. Variability at the fundamental tidal periods is about half that expected from an inverse barotropic tide model for the Ross Sea, suggesting that the measured tidal signal in Cice may be used to diagnose sea ice mechanical properties and ice/ocean coupling. Key Points We can extract tidal signals in sea ice concentration from satellite data Tides are the largest signal in sea ice concentration in the northern Ross Sea Measured tidal divergence is a test of ice mechanics and ocean/ice interactions ©2013. American Geophysical Union. All Rights Reserved.
St-Laurent P.,Center for Coastal Physical Oceanography |
Klinck J.M.,Center for Coastal Physical Oceanography |
Dinniman M.S.,Center for Coastal Physical Oceanography
Journal of Physical Oceanography | Year: 2013
Oceanic exchanges across the continental shelves of Antarctica play an important role in biological systems and the mass balance of ice sheets. The focus of this study is on the mechanisms responsible for the circulation of warm Circumpolar Deep Water (CDW) within troughs running perpendicular to the continental shelf. This is examined using process-oriented numerical experiments with an eddy-resolving (1km) 3D ocean model that includes a static and thermodynamically active ice shelf. Three mechanisms that create a significant onshore flow within the trough are identified: 1) a deep onshore flow driven by the melt of the ice shelf, 2) interaction between the longshore mean flow and the trough, and 3) interaction between a Rossby wave along the shelf break and the trough. In each case the onshore flow is sufficient to maintain the warm temperatures underneath the ice shelf and basal melt rates of O(1 m yr21). The third mechanism in particular reproduces several features revealed by moorings from Marguerite Trough (Bellingshausen Sea): the temperature maximum at middepth, a stronger intrusion on the downstream edge of the trough, and the appearance of warm anticyclonic anomalies every week. Sensitivity experiments highlight the need to properly resolve the small baroclinic radii of these regions (5km on the shelf)-simulations at 3-km resolution cannot reproduce mechanism 3 and the associated heat transport. © 2013 American Meteorological Society.