Baroclinic transport in the Gulf of Alaska Part I. Seasonal variations of the Alaska Current

Temperature and salinity sections which intersect the Alaska Current are used to determine the baroclinic, geostropbic current on 21 occasions from 1975 to 1977. A sinusoidal curve-fitting technique is applied to these Alaska Current estimates and others available in the literature to statistically test the flow for an annual signal...

Baroclinic transport in the Gulf of Alaska Part II. A fresh water driven coastal current

A coastal geostrophic, baroclinic jet in the Gulf of Alaska is driven seasonally by fresh water discharge and winds. The narrow current (\u3c20 km) has a mean transport of 0.24 × 106 m3 s-1 (relative to 100 db) and velocities in excess of 66 cm s-1. The jet reaches a maximum in autumn, coincident with maximum fresh water discharge along the coast...

An Oceanographic Perspective on Early Human Migrations to the Americas

Early migrants to the Americas were likely seaworthy. Many archaeologists now agree that the first humans who traveled to the Americas more than 15,000 years before present (yr BP) used a coastal North Pacific route. Their initial migration was from northeastern Asia to Beringia where they settled for thousands to more than ten thousand years. Oceanographic conditions during the Last Glacial Maximum (18,000-24,000 yr BP) would have enhanced their boat journeys along the route from Beringia to the Pacific Northwest because the influx of freshwater that drives the opposing Alaska Coastal Current was small, global sea level was at least 120 m lower than at present, and necessary refugia existed. The onset of the Bølling- Allerød warming period, between 15,000 yr BP and 14,000 yr BP, accelerated the melting of the Cordilleran Ice Sheet. Rapid increases in freshwater influx would have hindered travel along the coast of Alaska and British Columbia as global sea levels rose 14-18 m in 340 years, submerging refugia that had been used as haul-out locations. The northward- flowing Alaska Coastal Current accelerated, making southward movement along the coast less likely. An increase in the challenges to migration beginning with the Bølling-Allerød until the Younger Dryas (12,800-11,600 yr BP) likely occurred and could have resulted in a migration hiatus

Ocean Warming and Freshening in the Northern Gulf of Alaska

Water column temperatures on the shelf in the northern Gulf of Alaska have increased more than 0.8 degrees C and vertical density stratification has increased since 1970 near Seward, Alaska throughout the 250 m depth. This high latitude marine system has low water temperatures, high rates of precipitation, glacial melting, high wind speeds and high rates of biological productivity. A more than 300 km alongshore shift ( locally westward) of isotherms is suggested. The observations are consistent with a conceptual ocean-atmosphere circulation model that employs coastal freshwater discharge, glacial ablation and wind forcing. Positive regional feedback mechanisms accelerate the discharge and poleward heat flux, leading to even higher temperatures, increased ocean stratification and increased storminess. This warming and ocean freshening will have significant impacts on the atmosphere and marine ecosystems of the Northeast Pacific, Bering Sea, Arctic Ocean and quite possibly global ocean circulation

Diuron From Maui Sugarcane Field Runoff is Potentially Harmful to Local Coral Reefs

In a grassroots effort to identify stressors influencing the health of Maui’s coral reefs, samples for the pre- and post-emergent herbicide, Diuron, were taken in July–August 2013, prior to, during, and after the passage of Tropical Storm Flossie on the south central coast of Maui, Hawaii. Diuron is routinely used on sugarcane fields adjacent to Hawaiian coastal waters and is a component of the anti-fouling paint used on small boats. It inhibits photosynthesis of terrestrial plants at concentrations as low as 0.1 parts per billion and can be lethal to endosymbiotic dinoflagellates in corals at concentrations less than 3 parts per billion, a concentration measured in runoff samples taken during this study. While Diuron was not detected in samples taken beyond the coastal outfall or in an adjacent boat basin, this effort provides evidence that a detectable influx of Diuron into Maui’s coastal waters can result from a single rain event. Further, this study will inform efforts to support a ban on the use of Diuron in the wet season and guide monitoring efforts to better understand the effects of Diuron in coastal areas

On the Nature of Winter Cooling and the Recent Temperature Shift on the Northern Gulf of Alaska Shelf

[1] In spring 2006 and 2007, northern Gulf of Alaska (GOA) shelf waters were ∼1.5°C below average throughout the similar to ∼250 m deep shelf and the salinity-dependent winter stratification was anomalously weak due to above (below) average surface (bottom) salinities. Spring 2007 and 2008 temperatures were also similar to ∼-1.5°C below average, but the anomalies were confined to the upper 100 m due to moderate salt stratification. Shelf temperatures in these 2 years were among the lowest observed since the early 1970s, thus interrupting an approximately 30-year warming trend. We examined winter cooling processes using historical conductivity-temperature-depth (CTD) profiles and mooring data from hydrographic station GAK1. The 2006 and 2007 cooling was associated with anomalously strong atmospheric heat loss in November 2006 and March 2007 and below-average fall runoff, which weakened winter stratification and allowed the late cooling to penetrate throughout the water column. In 2007 and 2008, early winter cooling was weak, fall runoff large, and stratification moderate at 100 m so that spring temperature anomalies were trapped to the upper 100 m. Analysis of the 40 year GAK1 CTD record indicates that winter averaged air-sea heat flux and salinity stratification anomalies explain 81% of the variation in deep (100-250 m) GOA temperatures. Although the timing and magnitude of winter runoff influences the shelf temperature distribution, temperature anomalies are a consequence of three-dimensional circulation and mixing processes. These involve the complex, but poorly understood, interplay among the air-sea heat flux; the ocean heat flux convergences; the stabilizing influence of runoff; and the destabilizing effects of cooling, vertical mixing, and the wind-driven cross-shelf buoyancy flux

Direct Observation of Propagating Gigahertz Coherent Guided Acoustic Phonons in Free Standing Single Copper Nanowires

We report on gigahertz acoustic phonon waveguiding in free-standing single copper nanowires studied by femtosecond transient reflectivity measurements. The results are discussed on the basis of the semianalytical resolution of the Pochhammer and Chree equation. The spreading of the generated Gaussian wave packet of two different modes is derived analytically and compared with the observed oscillations of the sample reflectivity. These experiments provide a unique way to independently obtain geometrical and material characterization. This direct observation of coherent guided acoustic phonons in a single nano-object is also the first step toward nanolateral size acoustic transducer and comprehensive studies of the thermal properties of nanowires

Bottom-Up Forcing And The Decline of Steller Sea Lions (Eumetopias jubatus) In Alaska: Assessing The Ocean Climate Hypothesis

Declines of Steller sea lion ( Eumetopias jubatus) populations in the Aleutian Islands and Gulf of Alaska could be a consequence of physical oceanographic changes associated with the 1976–77 climate regime shift. Changes in ocean climate are hypothesized to have affected the quantity, quality, and accessibility of prey, which in turn may have affected the rates of birth and death of sea lions. Recent studies of the spatial and temporal variations in the ocean climate system of the North Pacific support this hypothesis. Ocean climate changes appear to have created adaptive opportunities for various species that are preyed upon by Steller sea lions at mid-trophic levels. The east–west asymmetry of the oceanic response to climate forcing after 1976–77 is consistent with both the temporal aspect (populations decreased after the late 1970s) and the spatial aspect of the decline (western, but not eastern, sea lion populations decreased). These broad-scale climate variations appear to be modulated by regionally sensitive biogeographic structures along the Aleutian Islands and Gulf of Alaska, which include a transition point from coastal to open-ocean conditions at Samalga Pass westward along the Aleutian Islands. These transition points delineate distinct clusterings of different combinations of prey species, which are in turn correlated with differential population sizes and trajectories of Steller sea lions. Archaeological records spanning 4000 yr further indicate that sea lion populations have experienced major shifts in abundance in the past. Shifts in ocean climate are the most parsimonious underlying explanation for the broad suite of ecosystem changes that have been observed in the North Pacific Ocean in recent decades. [ABSTRACT FROM AUTHOR] Copyright of Fisheries Oceanography is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder\u27s express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.