The deglacial history of surface and intermediate water of the Bering Sea

Abstract

The lithology of deglacial sediments from the Bering Sea includes intervals of laminated or dysaerobic sediments. These intervals are contemporaneous with the occurrence of laminated sediments from the California margin and Gulf of California, which suggests widespread low-oxygen conditions at intermediate depths in the North Pacific Ocean. The cause could be reduced intermediate water ventilation, increased organic carbon flux, or a combination of the two. We infer abrupt decreases of planktonic foraminifer δ 18 O at 14,400 y BP and 11,650 y BP, which may be a combination of both freshening and warming. On the Shirshov Ridge, the abundance of sea-ice diatoms of the genus Nitzschia reach local maxima twice during the deglaciation, the latter of which may be an expression of the Younger Dryas. These findings expand the extent of the expression of deglacial millennial-scale climate events to include the northernmost Pacific.

Pulses of enhanced North Pacific Intermediate Water ventilation from the Okhotsk Sea and Bering Sea during the last deglaciation

“…Past changes in intermediate-depth oxygen concentrations in the northwest Pacific are often related to a substantial weakening of NPIW and its consequences in favoring the expansion of the oxygen minimum zone at the intermediate-water level (Schmittner et al, 2007;Cartapanis et al, 2011). During the Bølling/Allerød and early Holocene, hypoxic conditions marked the oceanic continental margins in the North Pacific, as well as in the Bering Sea and culminated in the formation of laminated sediments in some of those regions (Behl and Kennett, 1996;Cook et al, 2005;Kim et al, 2011). Under modern conditions, the Okhotsk Sea plays a central role as major contributor of fresh intermediate-water masses in the subarctic Pacific, physically coupled to sea-ice formation (Talley and Roemmich, 1991;Warner et al, 1996;Yasuda, 1997).…”

IODP Expedition 323—Pliocene and Pleistocene Paleoceanographic Changes in the Bering Sea

“…Prior to IODP Expedition 323 (Exp 323 hereafter), little was known about the sedimentology and climate history of the Bering Sea outside of a few piston core studies (Cook et al, 2005;Okazaki et al, 2005;Katsuki and Takahashi, 2005;Takahashi et al, 2005) and Sites 188 and 185 (Scholl and Creager, 1973), which were drilled by the Deep Sea Drilling Project (DSDP) in 1971 with old drilling technology and poor recovery. Past studies using piston cores in the Bering Sea indicated that, while current conditions in the Bering Sea promote seasonal sea-ice formation, during the Last Glacial Maximum (LGM) conditions sustained perennial or nearly perennial sea-ice cover (Tanaka and Takahashi, 2005), attesting to the potential utility of sedimentary records in the Bering Sea to examine past sea-ice distributions.…”

Expedition 323 summary

“…Interestingly, millennial cycles in climate proxy records are apparently correlative across the North Pacific, for example in the Bering Sea (Cook et al, 2005), the Sea of Okhotsk (Ono et al, 2005;Sakamoto et al, 2005), the California margin (e.g., Behl and Kennett, 1996), and the Sea of Japan (e.g., Tada et al, 1999). Although the mechanisms for the strong teleconnections between different sides of the North Pacific are not known, it has been proposed that changes in the source(s) of NPIW in the Okhotsk (Ono et al, 2005) or Bering seas could reach the California margin and influence the depth or strength of the OMZ (Cannariato and Kennett, 1999;Zheng et al, 2000), thereby connecting climate/ocean changes across the Pacific Ocean.…”

“…Prior to Integrated Ocean Drilling Program (IODP) Expedition 323, little was known about the sedimentology and climate history of the Bering Sea outside of a few piston core studies (e.g., Cook et al, 2005;Okazaki et al, 2005;Tanaka and Takahashi, 2005; and Deep Sea Drilling Project (DSDP) Sites 188 and 185 (Scholl and Creager, 1973), which were drilled in 1971 with old drilling technology and poor recovery. Past studies using piston cores in the Bering Sea indicate that although current conditions in the Bering Sea promote seasonal sea ice formation, during the Last Glacial Maximum (LGM), conditions sustained perennial or nearly pe-rennial sea ice cover , attesting to the potential usefulness of sedimentary records in the Bering Sea in examining sea ice distribution.…”