Solar forced Dansgaard-Oeschger events and their phase relation with solar proxies

TL;DR

This study demonstrates that the phase variability between solar activity proxies and Greenland climate during Dansgaard-Oeschger events is a natural outcome of nonlinear threshold dynamics influenced by solar forcing and noise, aligning with observed data.

Contribution

It refutes previous claims by showing that phase variability is an inherent feature of nonlinear models of DO events, reconciling solar forcing with climate proxy data.

Findings

Phase variability is a robust feature of nonlinear DO event models.

Threshold crossing dynamics explain the fluctuating phase relation.

Model results align with observed solar and climate proxy data.

Abstract

North Atlantic climate during glacial times was characterized by large-amplitude switchings, the Dansgaard-Oeschger (DO) events, with an apparent tendency to recur preferably in multiples of about 1470 years. Recent work interpreted these intervals as resulting from a subharmonic response of a highly nonlinear system to quasi-periodic solar forcing plus noise. This hypothesis was challenged as inconsistent with the observed variability in the phase relation between proxies of solar activity and Greenland climate. Here we reject the claim of inconsistency by showing that this phase variability is a robust, generic feature of the nonlinear dynamics of DO events, as described by a model. This variability is expected from the fact that the events are threshold crossing events, resulting from a cooperative process between the periodic forcing and the noise. This process produces a fluctuating phase relation with the periodic forcing, consistent with proxies of solar activity and Greenland climate.