The influence of global warming in Earth rotation speed

R Abarca Del Rio

doi:10.1007/s00585-999-0806-x

Abstract

Abstract. The tendency of the atmospheric angular momentum (AAM) is investigated using a 49-year set of monthly AAM data for the period January 1949-December 1997. This data set is constructed with zonal wind values from the reanalyses of NCEP/NCAR, used in conjunction with a variety of operationally produced AAM time series with different independent sources and lengths over 1976-1997. In all the analyzed AAM series the linear trend is found to be positive. Since the angular momentum of the atmosphere-earth system is conserved this corresponds to a net loss of angular momentum by the solid earth, therefore decreasing the Earth rotation speed and increasing the length of day (LOD). The AAM rise is significant to the budget of angular momentum of the global atmosphere-earth system; its value in milliseconds/century (ms/cy) is +0.56 ms/cy, corresponding to one-third of the estimated increase in LOD (+1.7 ms/cy). The major contribution to this secular trend in AAM comes from the equatorial Tropopause. This is consistent with results from a previous study using a simplified aqua-planet model to investigate the AAM variations due to near equatorial warming conditions. During the same time interval, 1949-1997, the global marine + land-surface temperature increases by about 0.79 °C/cy, showing a linear correspondence between surface temperature increase and global AAM of about 0.07 ms per 0.1 °C. These results imply that atmospheric angular momentum may be used as an independent index of the global atmosphere's dynamical response to the greenhouse forcing, and as such, the length of day may be used as an indirect indicator of global warming.Key words. Meteorology and atmospheric dynamics (general circulation) · Geodesy

Highlights

Introduction and motivationA distinguishing characteristic of the Earth's rotation is that the rate of rotation varies with time
This study based on the angular momentum (AAM) series computed with the zonal wind ®eld from NCAR/NCEP reanalyses shows that AAM present a measurable and clear positive trend over the last 49 years (1949±1997)
The trend in AAM is con®rmed by four independent data sets arising from dierent atmospheric operational centers, i.e. ECMWF, UKMO, Japan Meteorological Agency (JMA) and the NMC (

Summary

Introduction

Introduction and motivationA distinguishing characteristic of the Earth's rotation is that the rate of rotation varies with time. There must be an average accelerative non tidal component in the Earth's rotation which acts to decrease the LOD by A0.6 0.1 ms/cy. Using laserranging data from Lageos and Starlette satellites, it has been possible to measure changes in the Earth's gravitational ®eld and estimate secular variability in LOD due to internal mass distribution within the Earth system. These measurements range from A0.44 0.05 ms/cy to A0.61 0.05 ms/cy, consistent with values we should expect from a postglacial rebound process (Peltier and Jiang, 1996)

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Conclusion