Identification

Title

Diabatic upwelling in the Tropical Pacific: Seasonal and subseasonal variability

Abstract

The equatorial Pacific zonal circulation is composed of westward surface currents, the eastward equatorial undercurrent (EUC) along the thermocline, and upwelling in the eastern cold tongue. Part of this upwelling arises from water flowing along isotherms sloping up to the east, but it also includes water mass transformation and consequent diabatic (cross-isothermal) flow (w(ci)) that is a key element of surface-to-thermocline communication. In this study we investigate the mean seasonal cycle and subseasonal variability of cross-isothermal flow in the cold tongue using heat budget output from a high-resolution forced ocean model. Diabatic upwelling is present throughout the year with surface-layer solar-penetration-driven diabatic upwelling strongest in boreal spring and vertical mixing in the thermocline dominating during the rest of the year. The former constitutes warming of the surface layer by solar radiation rather than exchange of thermal energy between water parcels. The mixing-driven regime allows heat to be transferred to the core of the EUC by warming parcels at depth. On subseasonal time scales the passage of tropical instability waves (TIWs) enhances diabatic upwelling on and north of the equator. On the equator the TIWs enhance vertical shear and induce vertical-mixing-driven diabatic upwelling, while off the equator TIWs enhance the sub-5-daily eddy heat flux which enhances diabatic upwelling. Comparing the magnitudes of TIW, seasonal, and interannual w(ci) variability, we conclude that each time scale is associated with sizeable variance. Variability across all of these time scales needs to be taken into account when modeling or diagnosing the effects of mixing on equatorial upwelling.

Resource type

document

Resource locator

Unique resource identifier

code

https://n2t.org/ark:/85065/d7x06bx1

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

keyword value

Text

originating controlled vocabulary

title

Resource Type

reference date

date type

publication

effective date

2016-01-01T00:00:00Z

Geographic location

West bounding longitude

East bounding longitude

North bounding latitude

South bounding latitude

Temporal reference

Temporal extent

Begin position

End position

Dataset reference date

date type

publication

effective date

2022-11-01T00:00:00Z

Frequency of update

Quality and validity

Lineage

Conformity

Data format

name of format

version of format

Constraints related to access and use

Constraint set

Use constraints

Limitations on public access

None

Responsible organisations

Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

responsible party role

pointOfContact

Metadata on metadata

Metadata point of contact