DOI: 10.58160/rp17havtz9yrq3sx
title: The influence of land distribution, areal extent and albedo on Mesoarchaean climate - global tas temperatures

description: Climate change in the Mesoarchaean potentially played a pivotal role in facilitating gold mobilisation and deposition, ultimately contributing to the formation of the Witwatersrand gold province in the Kaapvaal Craton (South Africa) – the world’s largest known gold province. Almost all of the gold there occurs in the 2.90 – 2.79 Ga Central Rand Group, whereas the underlying 2.95 - 2.91 Ga West Rand Group, despite similar sedimentology, is essentially barren. This has been explained by differing degrees of chemical weathering, with intense weathering in Central Rand Group times having facilitated gold leaching from the Archaean hinterland. However, the drivers of this climatic change remain unsolved. To investigate this, we performed 140 simulations using the Planet Simulator, an Earth system model of intermediate complexity. We systematically assessed the effects of varying land distributions (diagonal, central, polar), land surface fractions (8–28 %), atmospheric CO₂-equivalent concentrations (3–30 %), and surface albedo (0.15–0.30). In addition to the expected strong dependence of global mean temperature on atmospheric greenhouse gas concentration, our results show reduced seasonality at higher atm. CO₂-equivalents. Increasing land area generally leads to cooling, except at low CO2-equivalent concentrations (3-5 %) and low albedo (&lt;0.2). When land exceeds ~13 % of total Earth’s surface, it starts to have a pronounced effect on global climate. Among the spatial configurations, diagonal land distribution shows the highest climate sensitivity. The climatic shift around 2.9 Ga may be linked to emergence of extensive low-albedo (&lt;0.2) surfaces (e.g., mafic/ultramafic rocks) and/or to the latitudinal drift of the Kaapvaal Craton into a more radiatively sensitive zone.

This dataset contains global 2-meter above the ground temperature (tas) at a horizontal resolution of T21 (64 x 32 grid points). The data are separated into two experimental configurations: (1) the effects of global land distribution and (2) the global effects of surface albedo. 


 Experiment 1: Effects of Global Land Distribution 

This experiment investigated the influence of Mesoarchaean land distribution and pattern on global climate, focusing on the global mean near-surface air temperature (tas). Three idealised continental configurations were implemented, representing diagonal, central and polar land distribution. For each configuration the total land fraction relative to the planetary surface area was systematically varied in four steps: 8%, 13%, 20% and 28%. 

Experiment 2: Global Effects of Albedo 

In this experiment, only the diagonal land distribution with different fractions was used, while the surface albedo was systematically varied to assess its climatic impact. The prescribed albedo values were 0.15, 0.20, 0.25 and 0.30. 


All simulations were performed using the Planet Simulator (PlaSim; Freadrich et al. 2005), an intermediate-complexity general circulation model. Postprocessing was conducted using PlaSim’s integrated postprocessor. The resulting data are provided in NetCDF format, representing 50-year simulations with the variable tas defined on the dimensions [long(64), lat(32), time (18263)].
description: R
description: CDO