Interdecadal changes in mesoscale eddy variance in the Gulf of Alaska circulation: Possible implications for the Steller sea lion decline

Miller, Arthur J.; Lorenzo, Emanuele Di; Neilson, Douglas J.; Kim, Heyjin; Capotondi, Antonietta; Alexander, Michael A.; Bograd, Steven J.; Mendelssohn, Roy; Hedstrom, Kate; Musgrave, David

doi:10.3137/ao.430303

Cited by 20 publications

(19 citation statements)

References 38 publications

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“…larvae in the boundaries of anticyclonic features, demonstrated in the present study, indicate that these smaller-scale oceanographic features may affect the life histories of some medium/large pelagic fishes. This would suggest that future research should incorporate higher resolution sampling of the biological and physical environment than generally occurs in most field studies and should attempt to resolve the extent to which the nature and frequency of formation of smaller-scale oceanographic features, such as eddies, are in fact predictably driven by larger-scale oceanographic changes (Glenn & Ebbesmeyer 1994, Miller et al 2005). …”

Section: Discussionmentioning

confidence: 99%

Varying mesoscale structures influence larval fish distribution in the northern Gulf of Mexico

David

Bringas²,

Goñi³

et al. 2012

Mar. Ecol. Prog. Ser.

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The variability of mesoscale circulation structures in the Gulf of Mexico (GOM) was examined using satellite altimeter data collected between 1992 and 2008, and linkages between ocean circulation and the spatial distribution of larval fish were assessed. The abundance and distribution of the larvae of 5 pelagic fish taxa (Auxis spp., Euthynnus alleteratus, Thunnus thynnus, other Thunnus spp., and Coryphaena spp.) were estimated from surveys conducted by the National Oceanic and Atmospheric Administration National Marine Fisheries Service each spring between 1993 and 2007. We observed a tendency for higher northward extension of the Loop Current (LC) during spring each year, with maximum northern penetration in summer, although the exact location of the LC varied from year to year. Generally, higher total larval abundances occurred during years of high northward penetration in a region that was crossed by the LC during its excursions. However, the interannual variability of the LC was not mirrored in a general increase or decrease of larval fish densities in the water masses out of the LC front. Further, the results show that larvae of T. thynnus and Auxis spp. were more abundant within the boundaries of anticyclonic features (usually between 148 to 158 cm of sea surface height) and within GOM common waters, defined as the background waters in between the boundaries of mesoscale features. Our findings suggest that the position and strength of anticyclone mesoscale features in the GOM define a favorable spawning habitat for the species examined. KEY WORDS: Fisheries oceanography · Mesoscale variability · Fronts and eddies · Loop Current · Ichthyoplankton distribution · Thunnus thynnusResale or republication not permitted without written consent of the publisher

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Section: Discussionmentioning

confidence: 99%

Varying mesoscale structures influence larval fish distribution in the northern Gulf of Mexico

David

Bringas²,

Goñi³

et al. 2012

Mar. Ecol. Prog. Ser.

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“…Miller et al 2005), as well as seasonal and interannual shifts in major currents that cross entire ocean basins (e.g. Alaskan Stream; Onishi & Ohtani 1999).…”

Section: Ocean Conditionsmentioning

confidence: 99%

Swimming depth and ocean currents affect transit costs in Steller sea lions Eumetopias jubatus

Hindle¹,

Rosen²,

Trites³

2010

Aquat. Biol.

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Transit costs associated with commuting between resting sites ashore and foraging areas at sea constitute an appreciable portion of foraging expenditures in pinnipeds. We examined transit swimming in 3 Steller sea lions Eumetopias jubatus trained to follow a moving boat at different speeds and depths. We measured dive behavior (duration) and focused specifically on activity measures (fore-flipper stroking and overall dynamic body acceleration [ODBA], an overall measure of body motion), which may be proxies for metabolic expenditure. Sea lions appeared to increase efficiency while transiting at depths that approached 3 times their body diameters (mean depth = 151 ± 1 cm SEM, n = 87). Although the response was not uniform for all tested scenarios, all of the observed significant adjustments to dive behavior and swimming mechanics supported an increased efficiency at this depth. An increase in transit speed (4.5 versus 3.5 knots [kn] surface speed) was associated with elevated flipper stroke frequencies (+ 5%) and stroke output (ODBA stroke -1 , + 48%). Sea lions transiting against the flow of a tidal current had reduced dive durations (-10%), while total ODBA was consistently elevated (+ 8% overall). This response to tidal flow was accompanied either by elevated ODBA stroke -1 (3.5 kn) or a parallel increase in stroking (4.5 kn). Our data demonstrate that small changes in the physical environment affect transiting in Steller sea lions, and imply that altered prey fields or changing ocean conditions can carry energetic consequences.

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“…Given the importance of mesoscale eddies for transport processes and ecosystem dynamics in the GOA we examine whether the changes in circulation after the 1976–1977 climate regime shift were associated with significant changes in eddy statistics. A preliminary attempt to address this issue was carried out by Miller et al [2005], using an earlier version of the ROMS model. The processes responsible for eddy generation and evolution are somewhat different in the eastern and western regions of the GOA [CDL07, and references therein].…”

Section: The 1976–1977 Climate Shiftmentioning

confidence: 99%

Low‐frequency variability in the Gulf of Alaska from coarse and eddy‐permitting ocean models

Capotondi¹,

Combes²,

Alexander³

et al. 2009

J. Geophys. Res.

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An eddy‐permitting ocean model of the northeast Pacific is used to examine the ocean adjustment to changing wind forcing in the Gulf of Alaska (GOA) at interannual‐to‐decadal timescales. It is found that the adjustment of the ocean model in the presence of mesoscale eddies is similar to that obtained with coarse‐resolution models. Local Ekman pumping plays a key role in forcing pycnocline depth variability and, to a lesser degree, sea surface height (SSH) variability in the center of the Alaska gyre and in some areas of the eastern and northern GOA. Westward Rossby wave propagation is evident in the SSH field along some latitudes but is less noticeable in the pycnocline depth field. Differences between SSH and pycnocline depth are also found when considering their relationship with the local forcing and leading modes of climate variability in the northeast Pacific. In the central GOA pycnocline depth variations are more clearly related to changes in the local Ekman pumping than SSH. While SSH is marginally correlated with both Pacific Decadal Oscillation (PDO) and North Pacific Gyre Oscillation (NPGO) indices, the pycnocline depth evolution is primarily related to NPGO variability. The intensity of the mesoscale eddy field increases with increasing circulation strength. The eddy field is generally more energetic after the 1976–1977 climate regime shift, when the gyre circulation intensified. In the western basin, where eddies primarily originate from intrinsic instabilities of the flow, variations in eddy kinetic energy are statistically significant correlated with the PDO index, indicating that eddy statistics may be inferred, to some degree, from the characteristics of the large‐scale flow.

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Interdecadal changes in mesoscale eddy variance in the Gulf of Alaska circulation: Possible implications for the Steller sea lion decline

Cited by 20 publications

References 38 publications

Varying mesoscale structures influence larval fish distribution in the northern Gulf of Mexico

Varying mesoscale structures influence larval fish distribution in the northern Gulf of Mexico

Swimming depth and ocean currents affect transit costs in Steller sea lions Eumetopias jubatus

Low‐frequency variability in the Gulf of Alaska from coarse and eddy‐permitting ocean models

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