Overview

Kuroshio Extension, conveyor belt for the North Pacific

As with other western boundary currents, the North Pacific's western boundary current has some of the largest air-sea fluxes found in the entire basin. It is one of the largest sinks of carbon in the North Pacific, has the characteristic maxima lobes of latent, sensible, and net surface heat loss, and is co-located with the Pacific storm track. The Kuroshio Extension (KE) current carries warm water at nearly 140 million cubic meters per second (140 Sv) eastward into the North Pacific. Wind driven Sverdrup transport accounts for about a third of this transport; the other 90 Sv is due to a tight recirculation gyre whose size varies on seasonal-decadal time scales. As cold dry air comes in contact with the warm KE and recirculation water, heat and moisture are extracted from the surface, resulting in deep convection (both in the atmosphere and ocean) and rainfall. Surface cooling and biological production lower the surface water CO₂ concentrations driving a net uptake. In late winter, surface water in the KE recirculation region is subducted into the permanent thermocline, forming Subtropical Mode Water, and sequestering carbon. Large dust clouds blowing eastward off Asia are visible in satellite images and can be traced all the way across the Pacific. Macro- and micro-nutrients, including iron, from the dust clouds can affect biological production and therefore may play an important role in the North Pacific carbon cycle.

KEO, an observatory for the Kuroshio Extension

The NOAA Kuroshio Extension Observatory (KEO) buoy was first deployed in June 2004, in the recirculation gyre south of the Kuroshio Extension at 144.6°E, 32.4°N. In February 2007, JAMSTEC deployed a second KEO buoy (JKEO) north of the Kuroshio Extension at 37.9°N, 146.6°E. Both KEO moorings carry a suite of meteorological sensors to measure winds, air temperature, relative humidity, rainfall, and solar and longwave radiation. With measurements of sea surface temperature and these surface meteorological measurements, the net air-sea heat, moisture and momentum fluxes can be computed. Surface and subsurface instrumentation includes temperature and salinity at 1 m to 500 m. Daily-averaged data are available in near-realtime (click on "Data" link above). In addition, both moorings carry a pCO₂ sensor for computation of the air-sea CO₂ flux. In the future, additional sensors may be added to the moorings.

KEO, part of the network of OceanSITES

KEO is one of NOAA's most recent contributions to the global network of time series stations. The network, now referred to as OCEAN Sustained Interdisciplinary Timeseries Environment observation System (OceanSITES), provides data for the science community, policy makers, and society in order to detect global climate and ecosystem changes, to describe/quantify them, to understand/explain them and to develop a capability to predict them.

The definition of an ocean timeseries site in the global system is that it has the following characteristics:

• in-situ observations of ocean/climate related quantities at a fixed geographic location/region
• sustained and continuous, contributing to a long-term record at the site
• autonomous moored sampling should be pursued to resolve high- frequency variability, to achieve high vertical resolution, and to obtain coincident multi- disciplinary sampling
• as an alternate to a mooring, shipboard observations from regular occupation of a site as at Ocean Weather Stations, historical sites or sites where moorings have not been established provide an alternate method
• site selection is determined by the value of the site as representative of one, and where possible more, meteorological, physical, or chemical area of interest

Funding for KEO

KEO is funded by the NOAA Climate Program's Office of Climate Observations. Much of the equipment was purchased for the TAO/EPIC field experiment which ended in November 2003. The TAO/EPIC project was funded by the NOAA Office of Global Programs' Pan American Climate Studies Program.