Identification

Title

On the intermittent occurrence of open-ocean polynyas in a multi-century high-resolution preindustrial earth system model simulation

Abstract

A 500-year-long high-resolution Community Earth System Model simulation under preindustrial radiative forcing produces Maud Rise Polynyas (MRPs) and Weddell Sea Polynya (WSP) events intermittently from decadal (MRP) to multidecadal (WSP) timescales. This periodicity is correlated with the variation of a regional Southern Annular Mode (SAM) index (evaluated regionally instead of circum-Antarctic) with corresponding variations of precipitation and winds over the Weddell Sea. A negative index causes the upper-ocean salinity to increase over multiple decades. Ultimately, brine rejection during seasonal sea-ice formation superimposed on the multidecadal increase raises the upper-ocean salinity beyond the tipping point for triggering deep convection that leads to polynyas. The initiation of polynya events is thus controlled by surface properties while the location of initiation is determined by bathymetric features. The persistent Taylor column effect, which is well represented by the high-resolution model topography of the Maud Rise seamount, preconditions this region for MRP initiation. Therefore, MRPs form more frequently than WSPs in the simulation. When the upper-ocean salinity is high, deep convection in the MRP region tends to be stronger, in which case MRPs are also more likely to grow into WSPs. Once WSPs emerge, they affect the regional atmospheric circulation and associated variables. We propose a regional coupled ocean-atmosphere mechanism to explain both the periodic emergence of polynyas and the periodic variation of the regional SAM index. Although the temperature and salinity of Weddell Deep Water show upward trends due to model drift, these density-compensating changes do not affect the frequency of polynya formation.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d7hx1h9q

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

2022-04-01T00:00:00Z

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