Consortium on the Ocean's Role in Climate

Investigators: U. Send, R. Davis, D. Rudnick, B. Cornuelle, D. Roemmich

Introduction

The goal of the CORC project is to develop, and operate, an observing system that describes the key features of ocean boundary currents.

Boundary currents are fast, transport large amounts of water and heat, and are subject to variability on many time scales. Their relevance to society comes through the effect they have on climate, and how they are in turn shaped by climate, as well as through the ecosystems they support.

Yet, there exists no national or international observing system that can capture these systems adequately. A vision paper with further details was presented at the OceanObs'09 conference and proposes an observing strategy combining multiple technologies at key locations. This CORC project is a step towards implementation of such a system.

CORC is making observations in two boundary current systems: the California Current in the Pacific Ocean off North America, and the New Guinea Undercurrent in the western tropical Pacific, specifically the Solomon Sea.

1. California Current

The California Current flows from north to south along the West Coast of the U.S. It is an eastern boundary current, with an upwelling regime that brings nutrient-rich waters to the surface; this, in turn, supports a complex ecosystem and large fishing industry. The characteristics of the current, and the ecosystem it supports, fluctuate on interannual to decadal time scales. CORC observations made off Southern California are analyzed together with data from other projects operating in the area (e.g. CalCOFI, CCE) to build a more comprehensive understanding of the dynamics of the California Current.

The California Current component of CORC has been in operation since 2008, under various configurations:

CORC locations during various phases of the project
Overlay: Daily-averaged Absolute Dynamic Topography
Source: Global Ocean 1/12° Physics Analysis and Forecast, CMEMS

Deployments:


2008 - 2012
From Fall 2008 through Fall 2012, CORC operated two moorings (CORC1 and CORC2), and five bottom landers, spanning the width of the California Current off Southern California. From the moorings, the strength of the California Current was computed as the geostrophic flow across the CORC1 - CORC2 section, referenced to zero flow at 3500 meters depth. To obtain the volume transport of the water, this was then integrated over the upper 300 meters of the water column. The resulting time series of water transport is an index of the strength of the California Current.

Comparing this index to satellite altimetry from AVISO, the difference in sea level anomaly between the two CORC sites captures the CORC index well. However, the altimetry data need to be "tuned" statistically in order to reproduce the CORC index:

Water volume transported by the California Current as observed by the CORC moorings (orange), and by satellite altimetry data regressed onto the mooring data (blue/green). Altimetry data are available in delayed-mode quality (blue) for earlier years, and in near-real time mode (green) for more recent years. The data in this figure are derived from the AVISO+/CMEMS Daily-averaged Absolute Dynamic Topography product, as in the color overlay for the above map figure.
Last Updated: UTC

Physically, this means that while satellite altimetry captures the surface velocity anomaly, it does not "know" how the current decays with depth. In addition, the representation of the mean current depends on the choice of a particular reference product. Tuning the altimetric signal to the mooring-derived transports sets both the mean flow and the vertical extent of the flow such that the altimetry data best represents the mooring data.

The data shown in the above figure can be downloaded here.

2012 - 2016
The 2012 - 2016 phase of CORC maintained a box-shaped array in the Southern California Current. The goal was to observe fluxes of mass and heat into the closed volume defined by the box. The layout of the array and the scientific rationale were motivated through a study by Roemmich (1989), which presented a similar box model based on CalCOFI samples, but which could not elucidate the changes over time that mooring-based time series observe.

Here, the northern box corners were defined by CalCOFI stations 55 and 80 along Line 80, co-located with existing long-term mooring observations from the CCE project. CORC augmented the CCE moorings with PIES (pressure + inverted ecdhosounder) instruments on the sea floor, and glider observations at, and inshore of the shallower CCE site. For the southern corners, CORC deployed two moorings (CORC3 and CORC4) at the equivalent locations further south along CalCOFI Line 90. These, too, were augmented with PIES at both sites, and with glider surveys at the shallower site. Point Conception, at the northern edge, and an existing mooring off Del Mar at the southern edge, act as natural extension points of the array towards the coast.

2017 - present
In 2017, CORC completed installation of an alongshore array from CalCOFI Line 90 in the south to Line 66 in the north. The array consists of three sites: the existing CORC3 mooring and PIES on Line 90 far offshore of San Diego, the existing CCE2 mooring and co-located CORC PIES on Line 80 off Point Conception, and MBARI's long-term M1 mooring with a co-located CORC5 PIES on Line 66 off Monterey. In addition to the PIES, CORC installed two additional temperature/salinity instruments on M1 in collaboration with MBARI, and is operating gliders near M1 and CCE2. The scientific goal is to observe the large-scale alongshore gradients in temperature, salinity, and pressure north and south of Point Conception.

2. New Guinea Undercurrent

The New Guinea Undercurrent flows from the southeast to the northwest through the Solomon Sea. It is a western boundary current that transports large amounts of heat and water into the warmest areas of the tropical Pacific. CORC observations are motivated by the interplay between this current and El Niño.

Beginning in 2012, two sites in the Solomon Sea have been occupied, each with a mooring and bottom lander. One site is located near Gizo, Solomon Islands, and the other near Misima, Papua New Guinea. These are located such that they bracket the flow of the New Guinea Undercurrent. Since 2007, other components of the project have been operating gliders on a similar section across the Solomon Sea.

CORC sites in the Solomon Sea

Data from the moorings and gliders are being analyzed to study the New Guinea Undercurrent, and how it varies throughout cycles of El Niño/La Niña.

Publications

  • Uwe Send, Lloyd Regier, Brent Jones (2013): Use of Underwater Gliders for Acoustic Data Retrieval from Subsurface Oceanographic Instrumentation and Bidirectional Communication in the Deep Ocean. J. Atmos. Oceanic Technol., vol. 30, pp. 984-998. doi: 10.1175/JTECH-D-11-00169.1.
  • Dean Roemmich, Philip Woodworth, Svetlana Jevrejeva, Sarah Purkey, Matthias Lankhorst, Uwe Send, and Nikolai Maximenko (2017): In Situ Observations Needed to Complement, Validate, and Interpret Satellite Altimetry. Pp. 113-148 of: Satellite Altimetry over Oceans and Land Surfaces, editors: Detlef Stammer and Anny Cazenave. ISBN 9781498743457. LCCN 2017013954. CRC Press.
  • Arachaporn Anutaliya, Uwe Send, Janet Sprintall, Julie L. McClean, Matthias Lankhorst, and Jannes Koelling (2019): Mooring and Seafloor Pressure End Point Measurements at the Southern Entrance of the Solomon Sea: Subseasonal to Interannual Flow Variability. J. Geophys. Res. Oceans, 124. doi: 10.1029/2019JC015157.

Published Datasets:

  • Lankhorst, Matthias; Send, Uwe (2016): Seawater temperature and salinity observed from the CORC1 and CORC2 moorings in the southern California Current (NE Pacific) from 2008-09-20 to 2012-11-14 (NCEI Accession 0137858). Version 1.2. NOAA National Centers for Environmental Information. Dataset. doi: 10.7289/V51834J4.
  • Lankhorst, Matthias; Nam, SungHyun; Send, Uwe (2016): Processed CTD and Water Sample Data from Research Vessel Roger Revelle, Expedition RR1214, in the NE Pacific in November 2012 (NCEI Accession 0156228). Version 1.1. NOAA National Centers for Environmental Information. Dataset. doi: 10.7289/V5MP519X.
  • Lankhorst, Matthias; Send, Uwe (2016): Processed CTD and Water Sample Data from Research Vessel Ocean Starr in the NE Pacific, Aug. 31 and Sept. 01, 2012 (NCEI Accession 0156932). Version 1.1. NOAA National Centers for Environmental Information. Dataset. doi: 10.7289/V58K774S.
  • Lankhorst, Matthias; Send, Uwe (2016): CTD and Water Sample Data from Research Vessel New Horizon in the NE Pacific, 19-22 September 2008 (NCEI Accession 0156931). Version 1.1. NOAA National Centers for Environmental Information. Dataset. doi: 10.7289/V54T6GD2.
  • Lankhorst, Matthias; Send, Uwe (2016): CTD Data from Research Vessel New Horizon in the NE Pacific, 15-20 December 2009 (NCEI Accession 0156689). Version 1.1. NOAA National Centers for Environmental Information. Dataset. doi: 10.7289/V53J3B0T.
  • Lankhorst, Matthias; Send, Uwe (2016): CTD and Water Sample Data from Research Vessel Robert Gordon Sproul in the NE Pacific, 24 October 2013 (NCEI Accession 0157082). Version 1.1. NOAA National Centers for Environmental Information. Dataset. doi: 10.7289/V5125QQ3.
  • Lankhorst, Matthias; Lowcher, Caroline; Send, Uwe (2017): CTD Data from Research Vessel New Horizon in the NE Pacific, 24 April - 01 May 2014 (NCEI Accession 0157699). Version 1.1. NOAA National Centers for Environmental Information. Dataset. doi: 10.7289/V5J38QMW.
  • Lankhorst, Matthias; Lowcher, Caroline; Send, Uwe (2017): CTD Data from NOAA Ship Reuben Lasker in the NE Pacific, 06-12 2016-10 (NCEI Accession 0157761). Version 1.1. NOAA National Centers for Environmental Information. Dataset. doi: 10.7289/V5DB7ZW5.
  • Lankhorst, Matthias; Lowcher, Caroline; Send, Uwe (2018): Seawater temperature and salinity observed from the CORC3 and CORC4 moorings in the southern California Current (NE Pacific) from 2012 to present (NCEI Accession 0163206). Version 2.2. NOAA National Centers for Environmental Information. Dataset. doi: 10.7289/V5PG1PXW.
  • Lankhorst, Matthias; Lowcher, Caroline; Send, Uwe (2018): Water temperature, salinity, dissolved oxygen profiles, and other data from CTD taken from the research vessel Bell M. Shimada, cruise SH-17-10, in the Northeast Pacific Ocean from 2017-11-01 to 2017-11-07 (NCEI Accession 0182942). NOAA National Centers for Environmental Information. Unpublished Dataset.

Acknowledgements

This project is made possible with funding from the NOAA Climate Program Office.
Data disclaimer: All data shown here come without warranty, express or implied. Use at your own risk, with appropriate caution.
Last Modified: 2023-05-30

Data/Website inquiries: jsevadjian@ucsd.edu