Identification

Title

Water isotopes during the Last Glacial Maximum: New General Circulation Model calculations

Abstract

The application of water isotopes to estimate the glacial-interglacial cycle of temperature (T) assumes the validity of the present-day spatial relationship between Ta and δ¹⁸O in precipitation (δ¹⁸Op) to estimate temporal changes of the temperature at a fixed location. We explored how and why the spatial relationship between annual mean Ta − δ¹⁸Op is different from the temporal relationship at one location. Our general circulation-isotope model exhibits a spatial slope of 1.22‰/°C between annual mean temperature at the top of the inversion layer (Ti ) and δ¹⁸Op over Antarctica, comparable to the observed value of 1.25‰/°C from Dahe et al. (1999) and using the Phillpot and Zillman (1970) relationship between surface temperature and the temperature of the inversion layer. Over the Southern Ocean (45°−60°S), local evaporation accounts for 50% of precipitation, and this evaporative flux (mean δ¹⁸Oe of ~−1‰) increases the δ¹⁸O of vapor (mean δ¹⁸Ov of ~−16‰). During the Last Glacial Maximum (LGM; 21,000 years ago), the isotopic composition of the vapor near the ice edge (~60°S) is calculated to be similar to the present values because evaporative recharge also accounts for ~50% of the precipitation over the Southern Ocean. As a result, the isotopic composition of vapor during the LGM is close to the present values at the ice edge. The apparent temporal slope over eastern Antarctica is half of the observed spatial slope. Our LGM experiment estimates an Antarctic mean annual temperature decrease of 13°C at Vostok, much larger than previous estimates. Our experiments with two specifications of LGM sea surface temperatures suggest that the value of the temporal slope is related to the temperature decrease over the Southern Ocean.

Resource type

document

Resource locator

Unique resource identifier

code

https://n2t.org/ark:/85065/d7n29x43

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

2008-10-08T00:00:00Z

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