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The Kuroshio Extension Observatory (KEO) and the Role of Air-Sea Interactions in the Kuroshio Extension

by Meghan Cronin

As PI and director of the Kuroshio Extension Observatory (KEO), Meghan Cronin is interested in understanding the nature and effects of the air-sea heat, moisture, momentum, and carbon dioxide fluxes in the Kuroshio Extension region.

Cronin Fig 1
Figure 1. The KEO (square) and J-KEO (diamond) buoys shown in relation to the climatological wintertime NCEP2 latent heat flux (shaded) in Wm-2 and the mean sea level height (contours). Mean sea level heights are courtesy B. Qiu.

 

The Kuroshio Extension Observatory, a time series reference site

The KEO buoy site at 32.4°N, 144.6°E is in the recirculation gyre south of the Kuroshio Extension (Fig. 1).  Funded through NOAA Office of Climate Observations, KEO is an OceanSITES time series reference site. It carries a full suite of sensors to monitor air-sea exchanges of heat, moisture, momentum, and carbon dioxide, as well as upper ocean temperature, salinity, and currents (Fig. 2).  KEO was also an element of the now-complete Kuroshio Extension System Study. For more information on KEO, see: http://www.pmel.noaa.gov/keo/.

With funding from JAMSTEC, Dr. Hiroshi Ichikawa and Dr. Cronin recently deployed a second surface mooring, J-KEO, north of the Kuroshio Extension, at 37.9°N, 146.6°E (Fig. 1). Ichikawa and Cronin are respectively the Japanese and U.S. partners on the proposed "Study of the temporal spatial variations of ocean surface fluxes in the North Pacific using the surface mooring network".

Cronin Fig 2
Figure 2. Select measurements from the Kuroshio Extension Observatory. Wire length of subsurface temperature are indicate in the bottom two panels. Because the mooring has a 1.4 scope (mooring line / water depth), the wire lengths must be combined with pressure measurements to determine the depth of the sensors.

The Role of Air-Sea Interactions in the Kuroshio Extension

Cronin is presently involved in several analyses that address:

  • What is the magnitude and variability of the air-sea fluxes in the Kuroshio Extension (KE) region? How well are these represented in satellite products and numerical weather prediction model forecasts and reanalyses?
  • What processes give rise to anomalous air-sea fluxes?
  • What processes control the SST and heat content variations on intraseasonal-to-interannual time scales?  What controls Subtropical Mode Water formation?
  • How do SST, heat content, and KE frontal variations affect storm development, clouds, and storm path? Are these effects enough to significantly influence the atmospheric circulation?
Cronin Fig 3
Figure 3. KEO surface measurements can be combined with the COARE v3.0 bulk algorithm to estimate the latent and sensible heat fluxes, and thus the net surface heat flux into the ocean. The oceanic frictional velocity is computed from the wind stress, estimated using the COARE bulk algorithm. The mixed layer depth, superimposed here on the subsurface temperature and salinity profiles, is estimated as a density step equivalent to .5C. The time series after May 2006 are from the telemetered daily-averaged data.
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