Changes in water properties around North Pacific intermediate water between the 1980s, 1990s and 2000s

Kouketsu, Shinya; Fukasawa, Masao; Sasano, Daisuke; Kumamoto, Yuichiro; Kawano, Takeshi; Uchida, Hiroshi; Doi, Toshimasa

doi:10.1016/j.dsr2.2009.12.007

Cited by 19 publications

(28 citation statements)

References 38 publications

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“…The increase of AOU in the NPIW (>0.5 mmol kg À1 yr À1 ) has also been found in the zonal section along 24 N around the date line between 1985 and 2005 [Kouketsu et al, 2010]. Because the trend of DO decrease that we found in NPIW was presumably related to the DO decrease in the Oyashio, it is important to understand how the signal of DO change in the Oyashio propagates into the intermediate layer of the North Pacific through the formation and circulation of NPIW.…”

Section: Influence Of Do Changes In the Npiw Formation Regionmentioning

confidence: 59%

Decrease of dissolved oxygen after the mid‐1980s in the western North Pacific subtropical gyre along the 137°E repeat section

Takatani¹,

Sasano²,

Nakano³

et al. 2012

Global Biogeochemical Cycles

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[1] The Japan Meteorological Agency has acquired dissolved oxygen (DO) concentration data each year since 1967 along the 137 E repeat section in the western North Pacific. In this data set we found significant regional temporal trends of decreasing or increasing DO concentrations on various isopycnal surfaces. DO decreases were particularly significant after the mid-1980s in the subtropical gyre; mean rates of DO change at 20-25 N for 1985-2010 À1 on 27.3 s q in the O 2 minimum Layer (OML). The cause of DO decrease differed among isopycnal surfaces. On density surfaces shallower than 26.0 s q (less than about 400 m), the deepening of isopycnal surfaces and decline of oxygen solubility due to ocean warming have had the greatest influence. In particular, between 25.2 s q and 25.8 s q near the NPSTMW their combined contributions accounted for >50% of the DO decrease. In the NPIW core at roughly 26.8 s q ($700 m), the decline in DO was attributable to the DO decrease in the formation region. In the OML between 27.0 s q and 27.3 s q ($1000 m), the DO decrease likely resulted from an increase in westward transport of low O 2 water due to strengthening of the subtropical gyre. The result of this study shows the importance of the long-term and high-frequency along the 137 E repeat section.Citation: Takatani, Y., D. Sasano, T. Nakano, T. Midorikawa, and M. Ishii (2012), Decrease of dissolved oxygen after the mid1980s in the western North Pacific subtropical gyre along the 137 E repeat section, Global Biogeochem. Cycles, 26, GB2013,

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Section: Influence Of Do Changes In the Npiw Formation Regionmentioning

confidence: 59%

Decrease of dissolved oxygen after the mid‐1980s in the western North Pacific subtropical gyre along the 137°E repeat section

Takatani¹,

Sasano²,

Nakano³

et al. 2012

Global Biogeochemical Cycles

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“…On the Washington margin, deepening isopycnals below the core of the California Undercurrent suggest that the warming we observe may, in part, reflect the geostrophic signature of increasing transport in the undercurrent [ Meinvielle and Johnson , ]. A change in the mixing ratio between Sea of Okhostk water and Oyashio Current water could also result in a temperature trend in the NPIW [ Kouketsu et al ., ]. However, over the long term, sea surface warming in water mass formation regions will be communicated throughout the remote ocean interior.…”

Section: Observed Long‐term Warming In the Cascadia Water Columnmentioning

confidence: 97%

Dissociation of Cascadia margin gas hydrates in response to contemporary ocean warming

Hautala

Solomon

Johnson

et al. 2014

Geophysical Research Letters

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Gas hydrates, pervasive in continental margin sediments, are expected to release methane in response to ocean warming, but the geographic range of dissociation and subsequent flux of methane to the ocean are not well constrained. Sediment column thermal models based on observed water column warming trends offshore Washington (USA) show that a substantial volume of gas hydrate along the entire Cascadia upper continental slope is vulnerable to modern climate change. Dissociation along the Washington sector of the Cascadia margin alone has the potential to release 45-80 Tg of methane by 2100. These results highlight the importance of lower latitude warming to global gas hydrate dynamics and suggest that contemporary warming and downslope retreat of the gas hydrate reservoir occur along a larger fraction of continental margins worldwide than previously recognized.

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“…Previous works have reported coherent patterns of multidecadal salinity changes within the oceans (Freeland et al 1997;Wong et al 1999Wong et al , 2001Dickson et al 2002;Curry et al 2003;Boyer et al 2005;Johnson and Lyman 2007;Gordon and Giulivi 2008;Cravatte et al 2009;Hosoda et al 2009;Roemmich and Gilson 2009;von Schuckmann et al 2009;Durack and Wijffels 2010;Helm et al 2010;Kouketsu et al 2010;Durack et al 2013;Skliris et al 2014). However, the cause of these salinity changes is not fully understood.…”

Section: Introductionmentioning

confidence: 97%

Simulating the Role of Surface Forcing on Observed Multidecadal Upper-Ocean Salinity Changes

et al. 2016

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The ocean's surface salinity field has changed over the observed record, driven by an intensification of the water cycle in response to global warming. However, the origin and causes of the coincident subsurface salinity changes are not fully understood. The relationship between imposed surface salinity and temperature changes and their corresponding subsurface changes is investigated using idealized ocean model experiments. The ocean's surface has warmed by about 0.58C (50 yr) 21 while the surface salinity pattern has amplified by about 8% per 50 years. The idealized experiments are constructed for a 50-yr period, allowing a qualitative comparison to the observed salinity and temperature changes previously reported. The comparison suggests that changes in both modeled surface salinity and temperature are required to replicate the three-dimensional pattern of observed salinity change. The results also show that the effects of surface changes in temperature and salinity act linearly on the changes in subsurface salinity. Surface salinity pattern amplification appears to be the leading driver of subsurface salinity change on depth surfaces; however, surface warming is also required to replicate the observed patterns of change on density surfaces. This is the result of isopycnal migration modified by the ocean surface warming, which produces significant salinity changes on density surfaces.

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Changes in water properties around North Pacific intermediate water between the 1980s, 1990s and 2000s

Cited by 19 publications

References 38 publications

Decrease of dissolved oxygen after the mid‐1980s in the western North Pacific subtropical gyre along the 137°E repeat section

Decrease of dissolved oxygen after the mid‐1980s in the western North Pacific subtropical gyre along the 137°E repeat section

Dissociation of Cascadia margin gas hydrates in response to contemporary ocean warming

Simulating the Role of Surface Forcing on Observed Multidecadal Upper-Ocean Salinity Changes

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