Circulation and hydrography in the northwestern Gulf of Alaska

Musgrave, David; Weingartner, Thomas J.; Royer, Thomas C.

doi:10.1016/0198-0149(92)90044-t

“…For instance, it is clear that seasonal variations of the Alaska gyre are small. Favorite et al (1976), Reed et al (1980), and Musgrave et al (1992) detected no significant annual signal in the Alaskan Stream. Royer (1981) computed a seasonal transport amplitude (referenced to 1500 db) of 1.2 Sv, with a maximum in March (versus a mean of 9.2 Sv).…”

Section: Discussionmentioning

confidence: 90%

Seasonal Evolution of Aleutian Low Pressure Systems: Implications for the North Pacific Subpolar Circulation*

Pickart

¹

,

Moore

²

,

Macdonald

³

et al. 2009

Journal of Physical Oceanography

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The seasonal change in the development of Aleutian low pressure systems from early fall to early winter is analyzed using a combination of meteorological reanalysis fields, satellite sea surface temperature (SST) data, and satellite wind data. The time period of the study is September-December 2002, although results are shown to be representative of the long-term climatology. Characteristics of the storms were documented as they progressed across the North Pacific, including their path, central pressure, deepening rate, and speed of translation. Clear patterns emerged. Storms tended to deepen in two distinct geographical locations-the Gulf of Alaska in early fall and the western North Pacific in late fall. In the Gulf of Alaska, a quasi-permanent ''notch'' in the SST distribution is argued to be of significance. The signature of the notch is imprinted in the atmosphere, resulting in a region of enhanced cyclonic potential vorticity in the lower troposphere that is conducive for storm development. Later in the season, as winter approaches and the Sea of Okhotsk becomes partially ice covered and cold, the air emanating from the Asian continent leads to enhanced baroclinicity in the region south of Kamchatka. This corresponds to enhanced storm cyclogenesis in that region. Consequently, there is a seasonal westward migration of the dominant lobe of the Aleutian low. The impact of the wind stress curl pattern resulting from these two regions of storm development on the oceanic circulation is investigated using historical hydrography. It is argued that the seasonal bimodal input of cyclonic vorticity from the wind may be partly responsible for the two distinct North Pacific subarctic gyres.

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“…However, it is believed that these are underestimates due to the presence of significant thermal wind shear at deeper depths and due to the barotropic component of the flow. Musgrave et al (1992) estimate that the baroclinic transport values computed in their study, referenced to 1000 db, are too small by a factor of 2. Geostrophy referenced to current meter records and to shipboard acoustic Doppler current profiler data boosts the transport of the Alaskan Stream to 23-24 Sv over the upper 1500 m (Warren and Owens 1988;Cokelet et al 1996) and to 28 Sv for the entire water column (Warren and Owens, 1988).…”

mentioning

confidence: 81%

“…The strength of the Alaska gyre has been estimated by measuring the strength of the Alaskan Stream (e.g., Reed et al 1980;Royer 1981;Musgrave et al 1992). Summaries of the transport estimates of this flow have been given by different authors (see the discussion in Cokelet et al 1996).…”

Section: A Overview Of the Circulationmentioning

confidence: 99%

Seasonal evolution of Aleutian low-pressure systems: Implications for the North Pacific sub-polar circulation

Pickart¹,

Moore²,

Macdonald³

et al. 2008

J Phys Oceanography

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The seasonal change in the development of Aleutian low pressure systems from early fall to early winter is analyzed using a combination of meteorological reanalysis fields, satellite sea surface temperature (SST) data, and satellite wind data. The time period of the study is September-December 2002, although results are shown to be representative of the long-term climatology. Characteristics of the storms were documented as they progressed across the North Pacific, including their path, central pressure, deepening rate, and speed of translation. Clear patterns emerged. Storms tended to deepen in two distinct geographical locations-the Gulf of Alaska in early fall and the western North Pacific in late fall. In the Gulf of Alaska, a quasi-permanent ''notch'' in the SST distribution is argued to be of significance. The signature of the notch is imprinted in the atmosphere, resulting in a region of enhanced cyclonic potential vorticity in the lower troposphere that is conducive for storm development. Later in the season, as winter approaches and the Sea of Okhotsk becomes partially ice covered and cold, the air emanating from the Asian continent leads to enhanced baroclinicity in the region south of Kamchatka. This corresponds to enhanced storm cyclogenesis in that region. Consequently, there is a seasonal westward migration of the dominant lobe of the Aleutian low. The impact of the wind stress curl pattern resulting from these two regions of storm development on the oceanic circulation is investigated using historical hydrography. It is argued that the seasonal bimodal input of cyclonic vorticity from the wind may be partly responsible for the two distinct North Pacific subarctic gyres.

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“…The foraging ranges of these females included the Gulf of Alaska gyre and the Alaska Current. Within this region, several mesoscale, often long-lived, anti-cyclonic eddies are generated (Tabata 1982, Musgrave et al 1992, Crawford 2002. Eddies are formed along the coast in winter between 51 and 60°N, and are often named after coastal cities near which they form, for example the 'Haida' and 'Sitka' eddies (Miller et al 2005).…”

Section: Ffas In Relation To Oceanographymentioning

confidence: 99%

“…Eddies are formed along the coast in winter between 51 and 60°N, and are often named after coastal cities near which they form, for example the 'Haida' and 'Sitka' eddies (Miller et al 2005). They are about 200 to 300 km in diameter and propagate westward into the gyre, carrying relatively warm and fresh water away from the continental margin (Musgrave et al 1992, Crawford 2002, 2005. The eddy core may be 1 or 2°C warmer than surrounding waters and characterised by a SLA of up to 0.4 m (Crawford 2002, Whitney & Robert 2002.…”

Section: Ffas In Relation To Oceanographymentioning

confidence: 99%

Linking foraging behaviour of the northern elephant seal with oceanography and bathymetry at mesoscales

Simmons¹,

Crocker²,

Kudela³

et al. 2007

Mar. Ecol. Prog. Ser.

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We examined the foraging behaviour of 12 adult female northern elephant seals in relation to mesoscale oceanographic features between 1995 and 1997. Females were divided into 3 groups based on the geographic region to which they migrated ('coastal', 'coastal-oceanic' and 'oceanic'). We defined focal foraging areas (FFAs) using satellite telemetry and average daily transit rates of ≤0.4 m s -1, and examined characteristics of FFAs with respect to sea surface temperature (SST), sea surface temperature gradient (SSTg), sea level anomaly (SLA) and bathymetry using logistic regression models. Shallow bathymetry was significant for the coastal grouping of females and we examined the prevalence of benthic dives using a dive index ratio (DI), calculated by dividing mean maximum dive depth (m) by ocean depth (m) at each location for all 12 females. An additional 6 adult males were included in this analysis to quantify and elucidate differences in benthic foraging mode between the sexes. DI comparisons revealed significantly greater prevalence of benthic diving in FFAs in males than females (χ 2 = 10.588, p < 0.01). However, one coastal female did show a higher occurrence of benthic dives in FFAs than other females, and had significantly greater rates of mass gain. The importance of each oceanographic variable differed between the 3 groups of females. Overall, model results showed SST to be the most influential factor related to FFAs. Additionally, 6 females had FFAs that were characterised by greater SSTg and higher SLA. These characteristics are consistent with anti-cyclonic eddies that occur throughout the range of elephant seals. Semipermanent eddies, such as the Haida and Sitka eddies of the Alaska gyre, may be particularly important in determining FFAs for some female northern elephant seals.

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Circulation and hydrography in the northwestern Gulf of Alaska

Cited by 55 publications

References 15 publications

Seasonal Evolution of Aleutian Low Pressure Systems: Implications for the North Pacific Subpolar Circulation*

Seasonal Evolution of Aleutian Low Pressure Systems: Implications for the North Pacific Subpolar Circulation*

Seasonal evolution of Aleutian low-pressure systems: Implications for the North Pacific sub-polar circulation

Linking foraging behaviour of the northern elephant seal with oceanography and bathymetry at mesoscales

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