Physical transport dynamics occurring at the ocean mesoscale (similar to 20 km - 200 km) largely determine the envi-ronment in which biogeochemical processes occur. As a result, understanding and modeling mesoscale transport is crucial for determining the physical modulations of the marine ecosystem. This review synthesizes current knowledge of mesoscale eddies and their impacts on the marine ecosystem across most of the North Pacific and its marginal Seas. The North Pacific domain north of 20 degrees N is divided in four regions, and for each region known, unknowns and known-unknowns are summarized with a focus on physical properties, physical-biogeochemical interactions, and the impacts of climate variability and change on the eddy field and on the marine ecosystem.

Adult and juvenile (age-1) walleye pollock (Gadus chalcogrammus) were sampled by the US NOAA Alaska Fisheries Science Center summer bottom trawl survey in 2010, 2017, 2018, and 2019 in the northeastern and southeastern Bering Sea, with profiles of temperature collected concurrently. Similarly, the Russian Research Institute of Fisheries and Oceanography, Pacific branch, collected adult and juvenile pollock and temperature profiles on summer bottom trawl surveys in the northwestern Bering Sea. Results from these surveys show that adult pollock abundance in recent years (2017, 2018, 2019) has increased in northern regions of the Bering Sea shelf in both the US and Russian sectors. Lower abundances, compared to historic means, were observed in southern regions of the shelf, suggesting the pollock moved directionally from the south to the north. We relate changes in pollock distribution in recent intermediate (2017) and warm, low-ice years (2018–2019) to a prior cold, high-ice year (2010) and describe how these observations relate to our longer time series. We link temperature data from bottom trawl surveys (US and Russian), sea-ice indices (retreat timing and extent), as well as model-based estimates of ocean circulation to changes in pollock distribution and examine potential environmental factors driving the observed changes. Changes in sea-ice and bottom temperature (e.g., reductions in ice extent and shrinking of the cold pool), and changes in circulation (stronger northward currents over the northeastern shelf in warmer years, particularly in 2018) led to changes in distributions of adult and age-1 pollock. Adult pollock were concentrated north of St. Lawrence Island and had larger longitudinal distributions in warm years, 2017–2019; whereas they had a more southerly and narrow distribution over the outer shelf in the cold year, 2010. Age-1 pollock had higher densities over the inner eastern shelf in 2017–2019 compared to 2010. Northward flow around St. Lawrence Island (particularly in the spring) alternated between stronger flow on the west side of the island in 2010 and 2017 and stronger flow on the east side of the island in 2018 and 2019; variations in flow may have impacted the location of prey and movement of feeding pollock to the Chukchi Sea. Size structure comparisons between NW, NE and SE sections of the Bering Sea shelf suggest that movement of fish between US and Russian waters may have been highest in 2019, one of the two warmest years, and lowest in 2010, the coldest year. Spatial comparisons of distributions and size structure across the Bering Sea help provide a comprehensive view of factors affecting the movement of this highly important commercial fish species.

A temperature and salinity hydrographic profile climatology is assembled, evaluated for data quality, and analyzed to assess changes of the Bering and Chukchi Sea continental shelves over seasonal to century-long time scales. The climatology informs description of the spatial distribution and temporal evolution of water masses over the two shelves, and quantification of changes in the magnitude and throughput of heat and fresh water. For the Chukchi Shelf, linear trend analysis of the integrated shelf heat content over its 1922-2018 period of record finds a significant summer and fall warming of 1.4 degrees C (0.14 +/- 0.07 degrees C decade(-1)); over 1990-2018 the warming rate tripled to 0.43 +/- 0.35 degrees C decade(-1). In contrast, the Bering Shelf's predominantly decadal-scale variability precludes detection of a water column warming trend over its 1966-2018 period of record, but sea surface temperature data show a significant warming of 0.22 +/- 0.10 degrees C decade(-1)) over the same time frame. Heat fluxes over 1979-2018 computed by the European Centre for Medium-Range Weather Forecast (ECMWF) ERAS reanalysis exhibit no record-length trend in the shelf-wide Bering surface heat fluxes, but the Chukchi Shelf cooling season (October-March) has a trend toward greater surface heat losses and its warming season (April-September) has a trend toward greater heat gains. The 2014-2018 half-decade exhibited unprecedented low winter and spring sea-ice cover in the Northern Bering and Chukchi seas, changes that coincided with reduced springtime surface albedo, increased spring absorption of solar radiation, and anomalously elevated water column heat content in summer and fall. Consequently, the warm ocean required additional time to cool to the freezing point in fall. Fall and winter ocean-to-atmosphere heat fluxes were anomalously large and associated with enhanced southerly winds and elevated surface air temperatures, which in turn promoted still lower sea-ice production, extent, and concentration anomalies. Likely reductions in sea-ice melt were associated with positive salinity anomalies on the Southeast Bering Shelf and along the continental slope over 2014-2018. Negative salinity anomalies during 2014-2018 on the central and northern Bering Shelf may be related to a combination of 1) long-term declines in salinity, 2) an increase of ice melt, and 3) a decline of brine production. We hypothesize that freshening on the Bering Shelf and in Bering Strait since 2000 are linked to net glacial ablation in the Gulf of Alaska watershed. We show that the heat engines of both the Bering and Chukchi shelves accelerated over 2014-2018, with increased surface heat flux exchanges and increased oceanic heat advection. During this time, the Chukchi Shelf delivered an additional 5-9 x 10(19) J yr(-1) (50-90 EJ yr(-1)) into the Arctic basin and/or sea-ice melt, relative to the climatology. A similar amount of excess heat (60 EJ yr(-1)) was delivered to the atmosphere, showing that the Chukchi Sea makes an out-sized contribution to Arctic amplification. A conceptual model that summarizes the controlling feedback loop for these Pacific Arctic changes relates heat content, sea ice, freshwater distributions, surface heat fluxes, and advective fluxes.

The eastern Bering Sea Shelf is characterized by high biological productivity, seasonal sea ice, and commercially important fisheries. Enhanced productivity is often associated with small‐scale oceanographic features. Our objective was to use an autonomous underwater vehicle to examine features typically missed by ~20‐km spaced shipboard sampling. A coastal glider (Oculus) sampled ~3 dives hr−1 with horizontal spacing of ~300 m per dive in August/September 2017. In the north‐south transition zone near St. Matthew Island, the glider sampled four eddy‐like features associated with weaker vertical stratification. These features had diameters of 15–20 km and were associated with higher surface chlorophyll. Shipboard data collected in the same region approximately a month later showed that a similar feature was associated with high concentrations of small copepods. Incorporating higher resolution sampling available with gliders into the Bering Sea observing network will improve our understanding of ecosystem response to patchiness in the system.

The highly productive northern Bering and Chukchi marine shelf ecosystem has long been dominated by strong seasonality in sea-ice and water temperatures. Extremely warm conditions from 2017 into 2019—including loss of ice cover across portions of the region in all three winters—were a marked change even from other recent warm years. Biological indicators suggest that this change of state could alter ecosystem structure and function. Here, we report observations of key physical drivers, biological responses and consequences for humans, including subsistence hunting, commercial fishing and industrial shipping. We consider whether observed state changes are indicative of future norms, whether an ecosystem transformation is already underway and, if so, whether shifts are synchronously functional and system wide or reveal a slower cascade of changes from the physical environment through the food web to human society. Understanding of this observed process of ecosystem reorganization may shed light on transformations occurring elsewhere. Exceptionally warm years in 2017–2019 have caused changes in the physical and biological characteristics of the Pacific Arctic Ocean. What these changes mean for the ecosystem and societal consequences will depend on if they are evidence of a transformation or anomalies in the system.

Arctic marine ecosystems are experiencing substantial changes associated with sea ice loss and surface warming. The most obvious and dramatic changes include earlier ice retreat and a longer ice-free season, particularly on Arctic inflow shelves, including the Barents Sea in the Atlantic Arctic and the northern Bering Sea and Chukchi Sea in the Pacific Arctic. The extreme variability observed in recent years in the Pacific Arctic is unparalleled in recorded history. This volume is devoted to studies that integrate research across various components of the Arctic marine ecosystem to better characterize these changes. The intent of this integrated approach is to better understand the linkages and interactions that shape ecosystem processes, influence timing and phenology of events, and inform predictions of future conditions. The studies presented in this Special Issue investigate processes in the Bering Sea, Chukchi Sea, and Beaufort Sea. The data derive from remote sensing, ship-based surveys, and integrated data products. The research presented includes time-series analyses on environmental change across the greater Pacific Arctic, heat flux, stratification and mixing dynamics, vertical structure, and wind and current patterns. It explores the influence of physical processes on, and seasonal and annual variability in, primary production, nutrient distribution, and the export of biogenic matter. It also examines the effects of oceanographic variability on zooplankton taxa, the distribution of larval fishes, age and growth in Arctic fishes, responses of salmon to warming, and variability in cetacean occurrence. These studies are designed to provide new insights on integrated ecosystem research in the Pacific Arctic, with a focus on improving understanding of ecosystem processes, timing and change. This volume marks the first in a series of research volumes supported by the North Pacific Research Board to integrate ecosystem research in the Pacific Arctic and to inform our collective understanding of the rapid transformation in this region.

Rapid changes in sea ice and ocean properties are occurring in the Chukchi Sea, and there is considerable uncertainty how these changes might influence nutrient distributions and ultimately primary productivity. Although inorganic nitrogen is a limiting nutrient, there are few reports on seasonal or interannual variability of nitrate, especially those focused on wintertime replenishment of nitrate. This study examined six years of hourly measurements of nitrate at multiple mooring locations off Icy Cape between 2010 and 2018 with a focus on winter replenishment in relation to northward transport. Nitrate concentrations are lowest in newly formed winter water, and rates of local nitrate replenishment appear low relative to the nutrient flux through Bering Strait. There is considerable interannual variability in transport over the northeastern shelf of the Chukchi Sea that is driven by northerly (weakens transport) and southerly (strengthens transport) wind events. Anomalously low nitrate concentrations were observed in the winter of 2011-2012 when transport was negligible, and locally formed, low nitrate winter water remained on the shelf. During winters with the highest transport (2010-2011, 2017-2018), pre-bloom (15 May) nitrate concentrations were high and closely resembled nitrate concentrations in the Bering Sea from the previous fall. In recent years, there has been an increase in southerly wind events. As these conditions enhance total transport and nutrient flux through Bering Strait, contemporary Bering Sea water is advected onto the northern Chukchi Sea shelf. In the presence of southerly wind events, nutrient measurements in the northern Bering Sea in fall can be used to predict pre-bloom nitrate concentrations available for sustaining primary production in the eastern Chukchi Sea the following spring. Since 2005, inorganic nitrogen concentrations in the northern Bering Sea have varied between 11 and 22 mu M; an indication that net community production over the eastern Chukchi Sea may have varied between similar to 30 and 70 g C m(-2) during this time.

We present the results of a study of the connectivity between Pacific cod spawning and nursery areas, and settlement of Pacific cod in the Gulf of Alaska. This work was conducted to address the hypothesis that spatial and temporal patterns of recruitment are related to variability in connectivity between spawning and nursery areas. To examine this hypothesis, we developed a Lagrangian, biophysical, individual-based model of Pacific cod early life history and dispersal using the Dispersal Model for Early Life Stages (DisMELS) framework. This model is driven by currents and scalars such as temperature from a version of the Regional Oceanographic Model System (ROMS) developed for the Gulf of Alaska. Results of our study show connectivity patterns predicted by the model that agree with our understanding (based on genetic analyses) that there is a high degree of localized retention in Pacific cod. The results indicate that the Shumagin Islands and Prince William Sound regions may serve as important collectors of Pacific cod recruits from upstream spawning areas. We also find correlations between individual-based model outputs and several large-scale climate indicators that appear to show settlement in several important nursery areas, and recruitment overall, are positively affected by slower gyre circulation in the Gulf of Alaska. We hypothesize that this is due to enhancement of retention, settlement in the Shumagin Island region, and reduction of transport of young cod out of the Gulf of Alaska to the southwest.

Little is known regarding the importance of early-life transport and dispersion mechanisms in determining recruitment variability for Pacific ocean perch (POP) in the Gulf of Alaska (GOA). These mechanisms influence the degree of, and variability in, connectivity between offshore natal areas (parturition sites) and inshore demersal nursery habitats for young-of-the year juveniles, and may thus play an important role in the "gauntlet" that individuals must survive from parturition to recruitment. As a first attempt to assess interannual variability in connectivity between natal and nursery areas for POP in the GOA in a synthetic manner, we developed a coupled biophysical individual-based model (IBM) for POP early life history and dispersal with simple representations of active vertical movement, passive horizontal movement, growth, and settlement in appropriate nursery habitat to integrate known early-life traits with variability in environmental forcing. We used an oceanographic model for the GOA based on the Regional Ocean Modeling system (ROMS) to provide the underlying daily physical environment to force the IBM for 1996-2011 and simulated hundreds of thousands of individual POP from parturition along the shelf break to settlement in inshore demersal nursery habitats as young-of-the-year. We used the IBM results to assess spatial patterns of annual "maximum potential" connectivity between presumed natal and nursery areas at along shore scales of similar to 150 km, as well as the interannual variability in these patterns. Results showed that, even in the absence of mortality, most ( > 70%) individuals were unsuccessful in dispersing from presumed natal areas along the continental shelf break to inshore nursery areas. For those that were successful, connectivity was directed in a counter clockwise fashion (southeast to northwest) around the GOA following prevailing current patterns. Typical dispersion distances were on the order of 100's of km along shore, much larger than those inferred from genetic sampling. Natal areas from which the highest fractions of successful individuals originated were in the southeast GOA, while the nursery areas most frequently reached by those successful individuals were in the central GOA. POP from natal areas in the western GOA were consistently exported from the system and likely contribute little to the GOA population, although they may contribute to populations in the Aleutian Islands and eastern Bering Sea. We also found that annual indices derived from the connectivity matrices were not very strongly related to any of a suite of basin- and regional-scale environmental indices, reflecting the overall complexity and scale of the pathways POP in the GOA may undertake during their early life stages and suggesting that multiple drivers operating at different spatial and temporal scales influence connectivity patterns. Finally, while our results indicate that interannual variability in physical transport may have a substantial impact on connectivity, we found little support for the hypothesis that this alone drives variability in POP recruitment.

Little is known about the mechanism of transport that enables age-0 sablefish (Anoplopoma fimbria) to reach suitable nursery sites from spawning locations far offshore, or the strength of the connection between individual spawning sites and nursery areas, or how variability in the strength of these connections may impact recruitment success. Using a model for the early life stages of sablefish, we explored the variability in connectivity between spawning and recruitment sites that can arise solely from interannual variability in environmental forcing and its impact on transport. Our major findings are that 1) the model indicates young sablefish settling in nursery areas in the Gulf of Alaska were most likely spawned in the eastern Gulf; 2) sablefish spawned in the western Gulf of Alaska are unlikely to settle anywhere in the Gulf, and are more likely to be advected farther west, perhaps to settle in the Aleutian islands or Bering Sea (to contribute to the Alaska population, they would have to undergo an active return migration as they mature); 3) total connectivity between all spawning sites and nursery areas showed stronger correlation with recruitment estimates than the strength of connections to or from specific regions; and 4) transport to St. John Baptist Bay, a known sablefish nursery area, was not the most probable end point for sablefish spawned throughout our Gulf of Alaska model domain. This suggests that young individuals arrive at this persistent nursery area due to directional swimming behavior, highly localized spawning, or small-scale currents not captured in the hydrographic model. The fact that no single correlate in our analysis had a very strong relationship to sablefish recruitment indicates that recruitment variability arises from complex interactions between the environment and the individual, and a possible disconnect in spatial scales between the Gulf of Alaska sablefish IBM and the broader sablefish stock assessment, which includes both the GOA and the Eastern Bering Sea, as well as possible contributions from Canadian stocks to the south. Our analyses determined that although the timing and extent of this transport shows significant interannual variability, both the location of likely sablefish spawning (source) areas and the comparative strength of connectivity between spawning and nursery sites appear to be relatively consistent year-to-year.

Synthesis of four decades of Gulf of Alaska ichthyoplankton data indicates that species diversity and total abundance peaks during spring, a common pattern in temperate and sub-arctic ocean regions due to synchrony with the spring peak in plankton production. Nevertheless, fish larvae occur in the plankton at all times of year and peak abundance periods vary significantly by species and habitat. Larval size at hatching and at transformation to the juvenile stage is also highly variable and associated with a variety of larval durations and temporal supply of larval cohorts to pelagic habitats. This phenological diversity represents variability in exposure and adaptation to seasonal cycles in the ocean. Water temperature, winds and currents, and availability of suitable zooplankton prey vary significantly on a seasonal scale affecting degrees of synchrony among larval species with optimal environmental conditions for growth, transport and survival. This synchrony is also affected by interannual shifts in the oceanographic environment, and different early life phenologies among species generate different sensitivities to such interannual variability. Early life history strategies and synchronies are evaluated here and environmental sensitivities are proposed for the numerically dominant species of fish larvae occurring in Gulf of Alaska plankton, including commercially and ecologically important species. For winter to early spring spawners, cold temperatures are an advantage in terms of slowing development so that larvae do not use up all their lipid reserves prior to optimal availability of suitable larval zooplankton prey. Interannual variability in winter temperature may therefore be a good indicator of survival outcomes, especially as influenced by the timing of the switch to exogenous feeding. Variability in temperature-influenced larval growth during late spring and summer months may be less consequential in maintaining synchrony with larval food availability for spring summer spawners. Rapid growth in association with warm summer conditions facilitates access to a wide size range of prey organisms and minimizes critical periods of vulnerability to trophic mismatch. The Gulf of Alaska is a highly advective environment; storms and alongshore winds promote onshore advection of surface waters. This onshore Ekman transport is strongest during winter and spring when deep water spawned larvae are most abundant over the slope and require access to the shelf. Enhanced shoreward transport of larvae in the canyons intersecting the slope is also an important mechanism. Interannual variability in such transport mechanisms may be critical in determining early ontogeny survival for these species. During all seasons, but especially spring and summer, there are species of larvae for which retention nearshore is vital for survival and mesoscale oceanographic features as well as larval behavioral abilities may be crucial. Annual patterns in phytoplankton and zooplankton production and abundance indicate high-amplitude variation in the composition of prey fields available to larvae, including variability in abundance and the size spectrum of organisms that larvae might encounter and consume. Food limitation seems less likely for larval species that are most abundant in spring summer than for species with peak abundance in winter-spring. It is probable that the more selective a species is in terms of zooplankton prey, the more susceptible that species is to atrophic mismatch. Species-specific intrinsic rates and morphological development during early ontogeny also influence the interaction of larvae with their environment, and larval growth trajectories can be quite different even among species with identical early life phenology. This insight clearly indicates that although phenology is critical, timing is not everything and all fish larvae are not equal. For the 23 species and two genera of fish in this study, a synoptic overview is provided of their early ontogeny environmental synchronies and proposed sensitivities. This ecological synthesis of phenologies helps us characterize vulnerability and resilience factors for intervals of the planktonic phase in the pelagic environment. It also identifies environmental signals that could be tested as species-specific ecosystem indicators of population trends for fish stocks in the Gulf of Alaska. Further, understanding seasonal dynamics in the ichthyoplankton is considered important for gauging food availability and energy flow more broadly in this and other pelagic ecosystems, as well as to understanding environmental forcing on the fish populations themselves.

AbstractEditor’s note: For easy download the posted pdf of the State of the Climate for 2019 is a low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.

Little is known regarding the early life transport and dispersion mechanisms, from offshore spawning areas to inshore nursery habitats, that potentially underlie recruitment variability for arrowtooth flounder in the Gulf of Alaska (GOA). We developed a biophysical individual-based model (IBM) for arrowtooth flounder early life history and dispersal with simple representations of swimming behavior, growth, and survival to explore the variability in connectivity between spawning and recruitment sites that can arise due solely to interannual variability in environmental forcing and its impact on transport. Results of our simulations for 1996-2011 show that, even in the absence of mortality, most (> 80%) individuals were unsuccessful in dispersing from presumed spawning areas along the continental shelf break to inshore nurseries in the GOA. For those that were successful, connectivity was directed in a counterclockwise fashion (southeast to northwest) following prevailing current patterns, with typical dispersion distances of 100 s of km alongshore. The most productive spawning areas were in the southeastern GOA (areas off Sitka and Cross Sound), while the most effective nursery areas were in the central and western GOA (Prince William Sound and North Kodiak areas). Arrowtooth flounder from spawning areas in the western GOA were exported from the system and likely contribute little to the population in the GOA, but may provide recruits to populations in the Aleutian Islands or eastern Bering Sea. We developed a suite of potential recruitment indices based on the connectivity results; however, none of these appeared to reflect estimated (age-1) recruitment to the population from a stock assessment model.

The interannual variability and trends of the Alaska Gyre and Gulf of Alaska (GOA) circulation are examined using meridional geostrophic transport from Argo temperature and salinity (2004-2017) and altimetric sea surface height (1993-2017). More than half of the top 1,500 m meridional transport variability in the Alaska Gyre is accounted for by a statistical mode strongly correlated with the Pacific Decadal Oscillation (PDO) index, consistent with the PDO exerting a major influence on North Pacific sea surface temperature variability. During a positive phase of the PDO, the zero-transport streamline separating the subtropical from the Alaska Gyre is shifted to the south from its mean position, while more transport is diverted northward, associated with a stronger and larger Alaska Gyre. Additionally, over the 25-year altimetric record there is a linear, increasing trend in strength of the Alaska Gyre (but not in areal extent), accompanied by an increasing trend for the incoming North Pacific Current. The effect of the PDO transport mode on GOA circulation is weak. Temperature and salinity volume averaged for the GOA covary with the PDO index, with warmer and fresher waters during a positive phase. Despite correlated anomalies for temperature, salinity, and northward transport into the GOA, however, geostrophic advection from the south contributes only minimally to the interannual variations of water properties in the GOA. An exception was the marine heat wave of 2013/2014 and its aftermath when temperature advection from the south played a more appreciable role for warming and subsequent cooling of the GOA. Plain Language Summary Variability of the ocean circulation in the Alaska Gyre is one of the factors influencing the rich ecosystem in the Gulf of Alaska. Improved understanding of the variability and trends of the Alaska Gyre is thus of prime concern, given its biologic and economic implications. Using data from the Global Argo program and satellite altimetry covering the 25-year period from 1993 to 2017, we diagnose the changes in Alaska Gyre structure and transport and how they fit in the larger picture of North Pacific global climate modes, such as the Pacific Decadal Oscillation (PDO). During a positive phase of the PDO, more transport is diverted northward, associated with a stronger and larger Alaska Gyre. Additionally, over the 25-year record the Alaska Gyre has continuously increased in strength (but not in size). While temperature and salinity in the Gulf of Alaska vary with the PDO, with warmer and fresher waters during a positive phase, advection from the south contributes only minimally to the year-to-year variations of water properties in the Gulf of Alaska, suggesting that these variations are mostly determined by local processes instead.

The continental shelf around Kodiak Island is incised with numerous submarine canyons, which play an important role in the cross-shelf transport of heat, salt, and nutrients, and the transport of ichthyoplankton of deep-spawning fish from the slope region into the shallow nursery grounds surrounding Kodiak Island. To explore the pathways and variability of flow, and the extent of tidal mixing within the canyons, moorings were placed in the Chiniak, Barnabas, and Amatuli troughs, and off the shelf from Resurrection Bay (Seward Line) and the Kenai Peninsula (Gore Point). In the troughs, intensified flow was evident near the trough walls, and flow was directed by bathymetry with inflow along the upstream (northern) side and outflow along the downstream (southern) side. The presence of mesoscale eddies in the gulf had no unique influence on currents or salinity in the troughs. Tidal mixing was strongest in Chiniak Trough, and this introduced cold, nutrient-rich bottom waters into the upper water column. Intensified bottom flow associated with the Alaskan Coastal Current was evident along the Seward Line and Gore Point, and directed toward the Kennedy-Stevenson Entrances, which are also regions of strong tidal mixing. Observations of tidal mixing were consistent with model results and satellite images showing cooler, phytoplankton-rich water in summer in the nursery grounds that surround Kodiak Island. Patterns of flow within the troughs and in Shelikof Strait were consistent with the springtime advance of ichthyoplankton across the shelf.

A fisheries oceanographic survey has collected physical and biological data from the eastern Gulf of Alaska during the month of July since 2010. The Sitka Eddy is a mesoscale feature that can impact physical and biological characteristics of the eastern Gulf of Alaska, and it can occur during July. Herein, the historical presence of a Sitka Eddy during July in this region was examined between 1993 and 2015 using satellite-derived altimetry, and interannual distributions of juvenile pink salmon (Oncorhynchus gorbuscha) were compared between 2010 and 2015. Biological characteristics of juvenile pink salmon and oceanographic conditions were compared between 2010 (strong eddy) and 2012 (weak eddy), and a further analysis across the Sitka Eddy was conducted for 2010. The Sitka Eddy occurs regularly in the eastern Gulf of Alaska, but strong events that occurred during July and likely to impact migrating salmon were only evident in 13% of the 23 years examined. Juvenile pink salmon catch distribution appeared to be deflected offshore by the Sitka Eddy in July of 2010, compared to nearshore distributions in 2011 through 2015. In 2010, temperatures were warmer, chlorophyll-a had a greater range, and juvenile pink salmon were distributed farther offshore as compared to 2012. Juvenile pink salmon diets were dominated by euphausiids in 2010 and large copepods in 2012. Additionally, Fulton's condition factor (K), insulin-like growth factor I (IGF-I), and whole body energy content (WBEC) were all lower in 2010. In 2010, temperatures reached a station maximum of 12.60 degrees C on the southeastern edge of the Sitka Eddy, and chlorophyll-a concentrations reached a local minimum of 0.077 mu g/l in the center of the eddy. Juvenile pink salmon from the eastern edge of the Sitka Eddy had significantly elevated values of K and IGF-I (p < 0.05), but WBEC did not vary significantly across the Sitka Eddy. Fish north of Cross Sound, which was outside of the Sitka Eddy, exhibited significantly lower K-values (p < 0.05) and relatively lower values of IGF-I and WBEC as compared to conspecifics south of Cross Sound. While the Sitka Eddy may act as an oasis offshore, when it impinges onto the shelf, it can squelch normal coastal production. By recognizing interannual variation in eddy magnitude, location, and impact to physical and biological characteristics, we can better understand and interpret interannual differences in the Gulf of Alaska ecosystem.