Seasonal Variability of Near-Surface Hydrography and Frontal Features in the Northern Gulf of Alaska and Prince William Sound

The meridional structure and seasonal cycles of near-surface hydrography and frontal features in the northern Gulf of Alaska and Prince William Sound are described from high-resolution measurements of near-surface temperature and salinity acquired by a vessel-mounted thermosalinograph. Near-surface temperature exhibits a well-defined seasonal cycle with little variation between basin and shelf waters. Near-surface salinity exhibits a well-defined seasonal cycle that is confined largely to the shelf waters reflecting the influence of coastal freshwater inputs. Prominent near-surface fronts at the shelf break, at the entrance to Prince William Sound, and in northern Prince William Sound intensify and weaken following the seasonal cycles of freshwater discharges into the northern Gulf of Alaska. These respective fronts are maintained by freshwater from the Alaska Coastal Current, the Copper River, and the snowfields and glaciers of northern Prince William Sound

Intrusion of warm Bering/Chukchi waters onto the shelf in the western Beaufort Sea

Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 114 (2009): C00A11, doi:10.1029/2008JC004870.Wind-driven changes in the path of warm Bering/Chukchi waters carried by the Alaska Coastal Current (ACC) through Barrow Canyon during late summer are described from high-resolution hydrography, acoustic Doppler current profiler–measured currents, and satellite-measured sea surface temperature imagery acquired from mid-August to mid-September 2005–2007 near Barrow, Alaska. Numerical simulations are used to provide a multidecadal context for these observational data. Four generalized wind regimes and associated circulation states are identified. When winds are from the east or east-southeast, the ACC jet tends to be relatively strong and flows adjacent to the shelf break along the southern flank of Barrow Canyon. These easterly winds drive inner shelf currents northwestward along the Alaskan Beaufort coast where they oppose significant eastward intrusions of warm water from Barrow Canyon onto the shelf. Because these easterly winds promote sea level set down over the Beaufort shelf and upwelling along the Beaufort slope, the ACC jet necessarily becomes weaker, broader, and displaced seaward from the Beaufort shelf break upon exiting Barrow Canyon. Winds from the northeast promote separation of the ACC from the southern flank of Barrow Canyon and establish an up-canyon current along the southern flank that is fed in part by waters from the western Beaufort shelf. When winds are weak or from the southwest, warm Bering/Chukchi waters from Barrow Canyon intrude onto the western Beaufort shelf.This work was supported in 2005 and 2006 by NSF grants OPP-0436131 and OPP-0436166. In 2007, this work received support through Woods Hole Oceanographic Institution- NOAA Cooperative Institute for Climate and Ocean Research Cooperative Agreement NA17RJ1223 and University of Alaska Fairbanks-NOAA Cooperative Institute for Arctic Research Cooperative Agreement NA17RJ1224. Additional support was provided by the James M. and Ruth P. Clark Arctic Research Initiative Fund at the Woods Hole Oceanographic Institution

Influence of oceanography on bowhead whale (Balaena mysticetus) foraging in the Chukchi Sea as inferred from animal-borne instrumentation

17 USC 105 interim-entered record; under review.The article of record as published may be found at https://doi.org/10.1016/j.csr.2021.104434The distribution of the Bering-Chukchi-Beaufort Sea population of bowhead whales (Balaena mysticetus) is largely centered in the Chukchi Sea in autumn (September–November), which is also when sea ice is at minimum extent allowing for increased ship traffic and industrial activity. Prior work paired autumn movements of bowhead whales in the Chukchi Sea with simulated hydrographic information and concluded whales followed relatively cold, saline waters of Pacific origin during migration (<0 ◦C, 31.5–34.25 psu). We attached six Satellite Relay Data Logger (SRDLs) that included miniaturized Conductivity, Temperature, and Depth (CTD) sensors capable of collecting temperature (T) and salinity (S) profiles as whales dove, allowing us to verify and expand upon prior habitat studies. Areas where transiting whales stopped and lingered (presumably to feed) were associated with colder surface temperatures and lingering behavior peaked where seafloor salinity was ~33 psu. Whales were also more likely to linger in areas where density gradients were lower at the seafloor. Whales targeted colder, more saline waters of Pacific origin, in agreement with our prior work. Surface and dive behavior of whales tagged in this and other studies suggests that most feeding in the central Chukchi Sea is occurring at depths below the surface, and that surface temperature is indicative of (a proxy for) other processes occurring at depth. We suggest that colder surface temperatures are indicative of the main pathway(s) by which zooplankton are advected through the Chukchi Sea. However, because similar movement patterns in other stocks of bowhead whales have been interpreted as the avoidance of thermal stress, we suggest more research is needed on thermoregulation before this question can be resolved.Global Model Analysis programDepartment of Energy RegionalOffice of Naval Research Arctic and Global Prediction programNational Science Foundation Arctic System Science progra

Ecological characteristics of core-use areas used by Bering–Chukchi–Beaufort (BCB) bowhead whales, 2006–2012

© The Author(s), 2014]. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Progress in Oceanography 136 (2015): 201-222, doi:10.1016/j.pocean.2014.08.012.The Bering–Chukchi–Beaufort (BCB) population of bowhead whales (Balaena mysticetus) ranges across the seasonally ice-covered waters of the Bering, Chukchi, and Beaufort seas. We used locations from 54 bowhead whales, obtained by satellite telemetry between 2006 and 2012, to define areas of concentrated use, termed “core-use areas”. We identified six primary core-use areas and describe the timing of use and physical characteristics (oceanography, sea ice, and winds) associated with these areas. In spring, most whales migrated from wintering grounds in the Bering Sea to the Cape Bathurst polynya, Canada (Area 1), and spent the most time in the vicinity of the halocline at depths <75 m, which are within the euphotic zone, where calanoid copepods ascend following winter diapause. Peak use of the polynya occurred between 7 May and 5 July; whales generally left in July, when copepods are expected to descend to deeper depths. Between 12 July and 25 September, most tagged whales were located in shallow shelf waters adjacent to the Tuktoyaktuk Peninsula, Canada (Area 2), where wind-driven upwelling promotes the concentration of calanoid copepods. Between 22 August and 2 November, whales also congregated near Point Barrow, Alaska (Area 3), where east winds promote upwelling that moves zooplankton onto the Beaufort shelf, and subsequent relaxation of these winds promoted zooplankton aggregations. Between 27 October and 8 January, whales congregated along the northern shore of Chukotka, Russia (Area 4), where zooplankton likely concentrated along a coastal front between the southeastward-flowing Siberian Coastal Current and northward-flowing Bering Sea waters. The two remaining core-use areas occurred in the Bering Sea: Anadyr Strait (Area 5), where peak use occurred between 29 November and 20 April, and the Gulf of Anadyr (Area 6), where peak use occurred between 4 December and 1 April; both areas exhibited highly fractured sea ice. Whales near the Gulf of Anadyr spent almost half of their time at depths between 75 and 100 m, usually near the seafloor, where a subsurface front between cold Anadyr Water and warmer Bering Shelf Water presumably aggregates zooplankton. The amount of time whales spent near the seafloor in the Gulf of Anadyr, where copepods (in diapause) and, possibly, euphausiids are expected to aggregate provides strong evidence that bowhead whales are feeding in winter. The timing of bowhead spring migration corresponds with when zooplankton are expected to begin their spring ascent in April. The core-use areas we identified are also generally known from other studies to have high densities of whales and we are confident these areas represent the majority of important feeding areas during the study (2006–2012). Other feeding areas, that we did not detect, likely existed during the study and we expect core-use area boundaries to shift in response to changing hydrographic conditions.This study is part of the Synthesis of Arctic Research (SOAR) and was funded in part by the U.S. Department of the Interior, Bureau of Ocean Energy Management, Environmental Studies Program through Interagency Agreement No. M11PG00034 with the U.S. Department of Commerce, National Oceanic and Atmospheric Administration (NOAA), Office of Oceanic and Atmospheric Research (OAR), Pacific Marine Environmental Laboratory (PMEL). Funding for this research was mainly provided by U.S. Minerals Management Service (now Bureau of Ocean Energy Management) under contracts M12PC00005, M10PS00192, and 01-05-CT39268, with the support and assistance from Charles Monnett and Jeffery Denton, and under Interagency Agreement No. M08PG20021 with NOAA-NMFS and Contract No. M10PC00085 with ADF&G. Work in Canada was also funded by the Fisheries Joint Management Committee, Ecosystem Research Initiative (DFO), and Panel for Energy Research and Development

Beluga whales in the western Beaufort Sea : current state of knowledge on timing, distribution, habitat use and environmental drivers

ECG was supported by a National Research Council-National Academy of Sciences Postdoctoral Fellowship.The seasonal and geographic patterns in the distribution, residency, and density of two populations (Chukchi and Beaufort) of beluga whales (Delphinapterus leucas) were examined using data from aerial surveys, passive acoustic recordings, and satellite telemetry to better understand this arctic species in the oceanographically complex and changing western Beaufort Sea. An aerial survey data-based model of beluga density highlights the Beaufort Sea slope as important habitat for belugas, with westerly regions becoming more important as summer progresses into fall. The Barrow Canyon region always had the highest relative densities of belugas from July-October. Passive acoustic data showed that beluga whales occupied the Beaufort slope and Beaufort Sea from early April until early November and passed each hydrophone location in three broad pulses during this time. These pulses likely represent the migrations of the two beluga populations: the first pulse in spring being from Beaufort animals, the second spring pulse Chukchi belugas, with the third, fall pulse a combination of both populations. Core-use and home range analyses of satellite-tagged belugas showed similar use of habitats as the aerial survey data, but also showed that it is predominantly the Chukchi population of belugas that uses the western Beaufort, with the exception of September when both populations overlap. Finally, an examination of these beluga datasets in the context of wind-driven changes in the local currents and water masses suggests that belugas are highly capable of adapting to oceanographic changes that may drive the distribution of their prey.PostprintPeer reviewe

CIRCULATION AND WATER PROPERTY VARIATIONS IN THE NEARSHORE ALASKAN BEAUFORT SEA (1999 – 2007)

Six years of current meter and water property data were collected year-round (1999 – 2007) from the landfast ice zone of the nearshore Alaskan Beaufort Sea (ABS). The data show large seasonal differences in the circulation that is defined by the set-up and breakup of the landfast ice. During the open water season (July – mid-October) mid-depth currents often exceed 20 cm-s-1, whereas during the landfast ice season (mid-October – June) these currents are generally \u3c10 cm-s-1. Tidal currents are feeble (\u3c3 cm-s-1) year-round and probably do not play a dynamically significant role on the inner shelf. Most (\u3e90%) of the current variability is in the along-shore direction year-round. In general the mean currents are not statistically different from zero over the whole record or in individual seasons. Open water currents are significantly correlated with the local winds, but currents beneath the landfast ice are not. Calculations conducted over both seasons suggest along-shore sea-level gradients are about 10-6, with the magnitude of these gradients being only slightly larger during the open water season than during the landfast ice season. These gradients are presumably set-up by the winds during the open water season, but their origin during the landfast ice season is unknown. However, preliminary model studies indicate that spatial variations in the underice friction coefficient are capable of establishing along-shore pressure gradients of this magnitude. During the open water season upwelling-favorable winds force westward flows that are strongly sheared in the vertical and with maximum currents at the surface. In contrast, downwelling favorable winds are weakly sheared in the vertical. The asymmetric current structure is presumed due to differences in stratification; strongly stratified during upwelling (westward) winds and weakly stratified during downwelling (eastward) winds. Cross-shore flows are generally small (~3 cm s-1) compared to along-shore currents. However, cross-shore flows of ~10 cm-s-1 were observed during the landfast ice season when the spring freshet resulted in an offshore spreading of a buoyant plume beneath the landfast ice. Although measured cross-shore flows are generally small, satellite imagery suggests that frontal instabilities associated with low-salinity nearshore plumes can transport inner shelf waters offshore to the Beaufort shelfbreak during the open water season. Observations from elsewhere in the Arctic suggest that cross-shore current speeds associated with instabilities can be as large as 30 cm s-1. Our results suggest that oil spilled beneath the landfast ice will stay within the vicinity of the oil spill source as current speeds will rarely exceed the threshold velocity required to transport an oil slick once it has attained its equilibrium thickness. We find that an underice oil spill has a 90% probability of remaining within 20 km of its origin over a 12-day period. Because of the broad spatial coherence in the flow field (~100 km in along-shore extent), underice currents could be monitored at one point and transmitted real-time to cleanup crews in the event of an underice spill. This information would verify the current speeds and whether oil would stay in the vicinity of the spill. Oil spilled during the open water season could be rapidly dispersed over great distances (~200 km in 12 days) in both the along- and cross-shore directions, however. Water properties also vary seasonally in response to ice formation and melting, the spring freshet, and wind-mixing. Salinities increase and temperatures decrease throughout the winter due to freezing and brine expulsion from sea-ice. During the spring freshet, the inner shelf is strongly stratified and remains so until the ice retreats and downwelling winds mix the water column. The annual suspended sediment cycle, based on transmissivity measurements, suggests rapid deposition of river borne sediments beneath the landfast ice during the spring freshet, with re-suspension and transport occurring throughout the open water season depending upon storm frequency. Re-suspension and transport is also vigorous during the formation of landfast ice and we conclude that much sediment is incorporated into the ice matrix at this time of the year. Ice-incorporated sediments are either transported with the ice or returned to the water column during melting the following summer. There are several important issues that we believe need to be addressed in the future. Modeling of the landfast ice zone requires an understanding of the role that ice-water friction plays in this region. Measurements of the spatially and temporally varying underice topography are critical to understanding the dynamics of this shelf. Second, the source and magnitude of the along-shore pressure gradients responsible for the underice currents needs to be determined. Third, it is not clear if the findings based on current measurements made in water depths ≤17 m apply to deeper portions of the landfast ice zone. Hence the cross-shore coherence in the underice circulation field needs to be determined. Fourth, the introduction of freshwater creates stratification that can lead to an asymmetric current response to wind-forcing during the open water season. Observations on the thermohaline structure of the Beaufort shelf are needed in order to understand and model the circulation field during the open water season. Cross-shore salinity fronts, established by river runoff, can become unstable and cause energetic cross-shelf flows capable of carrying pollutants far offshore. The dynamics and kinematics of these features need study. Fifth, sediments can adsorb pollutants and be incorporated into the ice along with oil; hence we recommend that consideration be given to the potential role that ice plays in the transport of sediments and pollutants on this shelf

Effect of Rainfall and Elevation on Specific Gravity of Coast Douglas-Fir

Analysis is made of the effects of five ranges of summer precipitation and three ranges of elevation on variation in specific gravity of Coast Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). The average specific gravity of Coast Douglas fir wood formed during single growing seasons varied from 0.52 for dry summers to 0.45 for wet summers. The negative linear trend held for three elevational levels. Wood produced under a combination of dry summers at low elevations averaged 0.55 specific gravity, whereas wood produced during wet summers at high elevations averaged only 0.44 specific gravity. Both percentage of latewood and thickness of latewood tracheid wall followed trends that were similar to those of specific gravity with summer rainfall and elevation