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The Bering Sea Ecosystem (1996) / Chapter Skim
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3 The Bering Sea Ecosystem: Geology, Physics, Chemistry, and Biology of Lower Trophic Levels
Pages 28-71

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From page 28...
... It exchanges water with the Arctic Ocean (through Bering Strait) and with the Pacific Ocean, into the Bering Sea from the Gulf of Alaska through the Aleutian Islands and into the northwest Pacific Ocean through Kamchatka Strait.
From page 29...
... THE BERING SEA ECOSYSTEM: GEOLOGY, PHYSICS, CHEMISTRY, AND BIOLOGY OF LOWER TROPHIC LEVELS 29 Figure 3.1 Physiographic features of the Bering Sea seafloor (adapted from Hood and Kelley, 1974)
From page 30...
... THE BERING SEA ECOSYSTEM: GEOLOGY, PHYSICS, CHEMISTRY, AND BIOLOGY OF LOWER TROPHIC LEVELS 30 Figure 3.2 A side-scan sonar image of the Bering Sea seafloor (EEZ-SCAN Scientific Staff, Atlas of the U.S. Economic Zone, Bering Sea, U.S.
From page 31...
... The Aleutian Basin is believed to be underlain by Mesozoic oceanic crust, and has been a center for sediment deposition of between 2 and 9 km since formation of the Aleutian Island arc. Deposition in smaller basins, such as the Bowers and Komandorsky, consists of a thinner sedimentary section of between 1 and 3 km.
From page 32...
... Sediments from the Russian coast deposited on the Bering Shelf are swept northward and eastward toward the Bering Strait as well. Materials derived from the Aleutian Islands and Kamchatka Peninsula are mostly deposited into the abyssal basins.
From page 33...
... north of the Aleutian island Unalaska.
From page 34...
... , and continuous to the north along the coast. Similar depths have been reported in Russia, with the southern permafrost limit found in the southcentral Kamchatka Peninsula, then stretching north to the Bering Strait; the highest content of ice is found in the deposits of the northern coastal plains and islands of Novosibirsk, where ice may constitute 10 to 15 percent of the soil at depths up to 10 m (30 feet)
From page 35...
... The ability for water exchange between the North Pacific and Bering Sea depends on the water depth in the passes. Since there are no deep passes east of 180¹ W, deep water exchange is restricted to the western side of this boundary.
From page 36...
... The northern North Pacific is the terminus for the world oceans deep circulation. Deep water formed in other high-latitude regions of the North Atlantic and Southern Ocean reaches the Gulf of Alaska after traveling for centuries.
From page 37...
... The exchange of water between the North Pacific Ocean and Bering Sea through the passes in the island arc is quite uncertain. Best estimates are that there is an outflow through Kamchatka Pass (21.0 Sv)
From page 38...
... THE BERING SEA ECOSYSTEM: GEOLOGY, PHYSICS, CHEMISTRY, AND BIOLOGY OF LOWER TROPHIC LEVELS 38 Figure 3.5 Bering Sea circulation schemes with water masses (Takenouti and Ohtani, 1974)
From page 39...
... . The transport of water through the Bering Strait from the Bering Slope Current is maintained by a north-south atmospheric pressure differential that tilts sea level down to the north (Coachman et al., 1975)
From page 40...
... THE BERING SEA ECOSYSTEM: GEOLOGY, PHYSICS, CHEMISTRY, AND BIOLOGY OF LOWER TROPHIC LEVELS 40 Figure 3.7 A cross-shelf advection model developed by the PROBES, (Processes and Resources of the Bering Sea Shelf) investigators and applied to organic matter partitioning and subsequent distributions of zooplankton and seabirds (McRoy, et al., 1986)
From page 41...
... Marine Chemistry of the North Pacific and Bering Sea Measurements of water column chemistry for the North Pacific and Bering Sea are very limited, especially in the coastal regions. Because the deep waters of the North Pacific are quite old, nutrients have accumulated in them during their passage though the deep regions of the world's oceans.
From page 42...
... . Figure 3.8b Maximum, mean, and minimum extent of ice edges for March 15 in the region of the Bering Sea and Arctic Ocean for the area centered on the Bering Strait, 1973–86 (Niebauer and Schell, 1993)
From page 43...
... suggests that changes in sea surface temperatures in the high-latitude North Pacific might be caused by changes in atmospheric turbidity as influenced by volcanic eruptions. Interdecadal sea surface temperature changes at high latitude are thought to be caused by lunar nodal tide forcing (Loder and Garrett, 1978; Maksimov and Smirnov, 1965; Royer, 1993)
From page 44...
... . The seasonal progression of the storm tracks over the North Pacific and Bering Sea could lead to a large seasonal variability in the ocean circulation, especially over the shelf and near shore.
From page 45...
... . A tantalizing choice for the possible forcing of interannual upper ocean temperature fluctuations in the northern North Pacific is the teleconnection from tropical forcing, that is, ENSO events with periodicities of three to six years.
From page 46...
... THE BERING SEA ECOSYSTEM: GEOLOGY, PHYSICS, CHEMISTRY, AND BIOLOGY OF LOWER TROPHIC LEVELS 46 Figure 3.9 Time series of mean North Pacific sea level pressures averaged over 30°-65° N, 160° E to 140° W for the months of November through March beginning in 1925 and smoothed with the low pass filter (Updated from Trenberth and Hurrell, 1994)
From page 47...
... Top panel shows Trenberth and Hurrell's (1994) North Pacific index (normalized)
From page 48...
... . Figure 3.11 Interdecadal changes in the sea surface temperature of the Gulf of Alaska and Bering Sea since 1947 (Committee on the Bering Sea Ecosystem)
From page 49...
... . A primary feature of the PNA is the Aleutian Low, and during ENSO events it deepens and moves southwestward during the North Pacific winter (Bjerknes, 1969)
From page 50...
... Thus, seasonal responses to wind forcing remain uncertain. The heat, salt, and nutrient supply for the Bering Sea depends on the exchange of water between the Bering Sea, North Pacific, and Arctic Ocean.
From page 51...
... THE BERING SEA ECOSYSTEM: GEOLOGY, PHYSICS, CHEMISTRY, AND BIOLOGY OF LOWER TROPHIC LEVELS 51 Figure 3.13 Sitka air temperature anomalies with least squares fit of 18.6-year lunar nodal tide cycle (smooth curve, with anomalies smoothed by using a fifth-degree Butterworth filter with a five-year cutoff) (after Royer, 1993)
From page 52...
... have associated changes in the Bering Sea ice cover with atmospheric circulation changes caused by changes in heat and moisture advection. Summary Interannual variability in the North Pacific and Bering Sea exists on a variety of time scales and has multiple causes (Table 3.2)
From page 53...
... Changes in global atmospheric pressure patterns can create persistent blocking ridges over the North Pacific, leading to decadal and longer shifts in pressure patterns and storm tracks. These changes might be considered "regime shifts", which alter the timing of critical storm events that can affect biological productivity; they are discussed further below.
From page 54...
... Beyond this general setting, other processes lead to important mesoscale variability in patterns of primary production in the Bering Sea and very high production in several regions. These include the flow of Alaska Stream water from the Gulf of Alaska into the Bering Sea through passes in the Aleutian Island arc, upwelling at the edge of the continental shelf and along the Aleutian Island arc, and currents at the shelf edge and across the northern shelf.
From page 55...
... . Production in the middle domain is greater than in the coastal domain, because it is nearer the basin, the water column is deeper, and there is a larger initial nutrient inventory.
From page 56...
... , and total production is probably between 200 to 250 g C m-2 y-1. Figure 3.15 Generalized pattern of primary production in the Bering Sea and northern Gulf of Alaska (Springer and McRoy, in review)
From page 57...
... It is a comparatively narrow region with distinct physical characteristics and, apparently, a bountiful production regime. The shelf edge domain, or "green belt," apparently extends around the entire perimeter of the Bering Sea continental shelf and across the northern shelf, through Bering Strait, and into the Chukchi Sea.
From page 58...
... Neocalanus cristatus, N plumchrus, Eucalanus bungii, and Metridia pacifica are oceanic species found in deep water across the North Pacific.
From page 59...
... The Bering Slope Current system should respond to basin scale changes in wind forcing over the Bering Sea, although direct evidence of this is not available. Similarly, it might respond indirectly to changes in the Gulf of Alaska through the effects of wind-forced variations in the flow of the Alaska Stream through the Aleutian Island arc.
From page 60...
... . BIOLOGY OF LOWER TROPHIC LEVELS Benthic Production The benthic communities of the Bering Sea are dominated by a large variety of polychaetes, amphipods, gastropods, and bivalves.
From page 61...
... at 60° N, 149° W in the northern Gulf of Alaska and yearly zooplankton biomass values for the periods 1956–62 (circles) and 1980–89 (squares)
From page 62...
... . Regions of high overlying water column production in the Bering and Chukchi seas have a direct influence on underlying benthic biomass (Grebmeier, 1993; Grebmeier et al., 1988; Rowe and Phoel, 1991)
From page 63...
... THE BERING SEA ECOSYSTEM: GEOLOGY, PHYSICS, CHEMISTRY, AND BIOLOGY OF LOWER TROPHIC LEVELS 63 Figure 3.18 Variation of benthic biomass with latitude on the Bering and Chukchi sea shelves (vertical lines indicate standard deviation and brackets indicate the coefficient of variation around the mean) (Stoker, 1981.)
From page 64...
... 10–30 (11, 12) Anadyr Water Southern Chukchi Sea Alaska Coastal Water 80 (8)
From page 65...
... THE BERING SEA ECOSYSTEM: GEOLOGY, PHYSICS, CHEMISTRY, AND BIOLOGY OF LOWER TROPHIC LEVELS 65 Figure 3.19 Total infaunal and epifaunal biomass in the southeastern Bering Sea (Haflinger, 1981)
From page 66...
... THE BERING SEA ECOSYSTEM: GEOLOGY, PHYSICS, CHEMISTRY, AND BIOLOGY OF LOWER TROPHIC LEVELS 66 Figure 3.20 Distribution of macrofaunal benthic biomass on the shelves of the northern Bering and Chukchi seas (Grebmeier, 1993)
From page 67...
... THE BERING SEA ECOSYSTEM: GEOLOGY, PHYSICS, CHEMISTRY, AND BIOLOGY OF LOWER TROPHIC LEVELS 67 Figure 3.21 Distribution of macrofaunal biomass on the northern shelf of the Bering Sea, June 1990 (Grebmeier and Cooper, 1995)
From page 68...
... THE BERING SEA ECOSYSTEM: GEOLOGY, PHYSICS, CHEMISTRY, AND BIOLOGY OF LOWER TROPHIC LEVELS 68 Figure 3.22 Distribution of king and Tanner crabs in the eastern Bering Sea (vertical lines indicate areas of high abundance)
From page 69...
... give rise to different benthic communities in polar systems. In the northern Bering and southern Chukchi seas, benthic standing stock is correlated with water column production (Grebmeier, 1993; Grebmeier and McRoy, 1989)
From page 70...
... indicates that any decrease in carbon flux would be detrimental to such large species, shifting the population to smaller species that would out compete the large amphipods, thus changing the benthic community structure. In addition, the low bottom temperatures of the northern Bering Sea exclude most bottom-feeding fish (Bakkala, 1981; Jewett and Feder, 1980)
From page 71...
... . Studies over both interannual and decadal time scales are required to elucidate factors influencing observed changes in benthic populations in the northern Bering Sea.


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