Balance of Volume Transports between Horizontal Circulation and Meridional Overturn in the North Pacific Subarctic Region

ABSTRACTSurface radiocarbon (Δ14C) in the North Pacific has been monitored using a commercial volunteer observation ship since the early 2000s. Here we report the temporal and spatial variations in Δ14C in the summer surface water when the surface ocean is vertically stratified over a 13-yr period, 2004–2016. The long-term Δ14C decreasing trend after the late 1970s in the subtropical region has continued to the present and the rate of decrease of the Kuroshio and Kuroshio Extension, North Pacific and California current areas is calculated to be –3.3, –5.2 and –3.3 ‰/yr, respectively. After 2012 the Δ14C of the Kuroshio and Kuroshio Extension area, however, has remained at an approximately constant value of around 50‰. The result may indicate that subtropical surface Δ14C in the western North Pacific has reached an equilibrium with atmospheric Δ14CO2. The Δ14C in the subarctic region is markedly lower than values in the subtropical region and it seems that the decreasing tendency of surface Δ14C has changed to an increasing tendency after 2010. The results may indicate that bomb-produced 14C, which has accumulated below the mixed layer in the past few decades, has been entrained into the surface layer by deep convection.

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Distribution and formation of the mesothermal structure (temperature inversions) in the North Pacific subarctic region

Journal of Geophysical Research Atmospheres ◽

10.1029/2000jc900020 ◽

2000 ◽

Vol 105 (C7) ◽

pp. 16885-16897 ◽

Cited By ~ 61

Author(s):

Hiromichi Ueno ◽

Ichiro Yasuda

Keyword(s):

North Pacific ◽

Subarctic Region ◽

The North ◽

Temperature Inversions ◽

The North Pacific

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Impacts of Physical and Biological Processes on Spatial and Temporal Variability of Particulate Organic Carbon in the North Pacific Ocean during 2003–2017

Scientific Reports ◽

10.1038/s41598-019-53025-4 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 2

Author(s):

Jun Yu ◽

Xiujun Wang ◽

Hang Fan ◽

Rong-Hua Zhang

Keyword(s):

Pacific Ocean ◽

Organic Carbon ◽

North Pacific ◽

Temporal Variability ◽

North Pacific Ocean ◽

Biological Processes ◽

Subtropical Region ◽

Subarctic Region ◽

The North ◽

The North Pacific

Abstract The North Pacific Ocean is a significant carbon sink region, but little is known about the dynamics of particulate organic carbon (POC) and the influences of physical and biological processes in this region at the basin scale. Here, we analysed high-resolution surface POC data derived from MODIS-Aqua during 2003–2017, together with satellite-derived sea surface chlorophyll and temperature (SST). There are large spatial and temporal variations in surface POC in the North Pacific. Surface POC is much lower in the subtropical region (<50 mg m−3) than in the subarctic region (>100 mg m−3), primarily resulting from the south-to-north variability in biological production. Our analyses show significant seasonal and interannual variability in surface POC. In particular, there is one peak in winter-spring in the western subtropical region and two peaks in late spring and fall in the western subarctic region. Surface POC is positively correlated with chlorophyll (r = ~1) and negatively correlated with SST (r = ~−0.45, P < 0.001) south of 45°N, indicating the strong influence of physically driven biological activity on the temporal variability of POC in the subtropical region. There is a significantly positive but relatively lower correlation coefficient (0.6–0.8) between POC and chlorophyll and an overall non-significantly positive correlation between POC and SST north of 45°N, reflecting the reduction in the POC standing stock due to the fast sinking of large particles. The climate modes of the Pacific Decadal Oscillation, El Niño–Southern Oscillation and North Pacific Gyre Oscillation have large impacts on POC in various seasons in the subtropical region and weak influences in the subarctic region. Surface POC was anomalously high after 2013 (increased by ~15%) across the basin, which might be the result of complex interactions of physical and biological processes associated with an anomalous warming event (the Blob).

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