Reply on RC2

Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> The warmer early Pliocene climate featured changes to global sea surface temperature (SST) patterns, namely a reduction to the equator-pole gradient and to the east-west SST gradient in the tropical Pacific, the so-called &ldquo;permanent El Ni&ntilde;o&rdquo;. Here we investigate the consequences of the SST changes to silicate weathering and thus to atmospheric CO₂ on geological timescales. Different SST patterns than today imply regional modifications of the hydrological cycle that directly affects continental silicate weathering in particular over tropical &ldquo;hotspots&rdquo; of weathering such as the Maritime continent, thus leading to a &ldquo;weatherability pattern effect&rdquo;. We explore the impact of Pliocene SST changes on weathering using climate model and silicate weathering model simulations, and deduce CO₂ and temperature at C cycle equilibrium between solid Earth degassing and silicate weathering. In general, we find large regional increases and decreases to weathering fluxes that largely cancel out one another. For permanent El Ni&ntilde;o conditions, weathering decreases outweigh the increases, leading to a small amplification of warming relative to the present-day by 0.4 &deg;C. The demise of permanent El Ni&ntilde;o could have had a small amplifying effect on cooling from the early Pliocene into the Pleistocene. For the reduced equator-pole gradient, the weathering increases and decreases largely cancel leading to no detectable difference in global temperature at C cycle equilibrium.