Milankovitch Forcing and Meridional Moisture Flux in the Atmosphere: Insight from a Zonally Averaged Ocean–Atmosphere Model

Abstract

A 1-Myr-long time-dependent solution of a zonally averaged ocean-atmosphere model subject to Milankovitch forcing is examined to gain insight into long-term changes in the planetary-scale meridional moisture flux in the atmosphere. The model components are a one-dimensional (latitudinal) atmospheric energy balance model with an active hydrological cycle and an ocean circulation model representing four basins (Atlantic, Indian, Pacific, and Southern Oceans). This study finds that the inclusion of an active hydrological cycle does not significantly modify the responses of annual-mean air and ocean temperatures to Milankovitch forcing found in previous integrations with a fixed hydrological cycle. Likewise, the meridional overturning circulation of the North Atlantic Ocean is not significantly affected by hydrological changes. Rather, it mainly responds to precessionally driven variations of ocean temperature in subsurface layers (between 70-and 500-m depth) of this basin. On the other hand, annual and zonal means of evaporation rate and meridional flux of moisture in the atmosphere respond notably to obliquity-driven changes in the meridional gradient of annual-mean insolation. Thus, when obliquity is decreased (increased), the meridional moisture flux in the atmosphere is intensified (weakened). This hydrological response is consistent with deuterium excess records from polar ice cores, which are characterized by dominant obliquity cycles.

Ranges of moisture-source temperature estimated from Antarctic ice cores stable isotope records over glacial–interglacial cycles

“…9) and without 100 kyr cycles. A recent modeling study (Antico et al, 2010) supports a large control of obliquity on latitudinal moisture transport.…”

Obliquity forcing of low-latitude climate

“…Furthermore, the role of precessioninduced changes in moisture content would need to be assessed as well. Another mechanism by which obliquity can affect highlatitude climate and glacial cycles through latitudinal insolation gradients has been proposed by Raymo and Nisancioglu (2003), Vettoretti and Peltier (2004), Antico et al (2010) and Mantsis (2011). These studies suggest that the poleward transport of heat, moisture and latent energy is increased during minimum obliquity due to the intensified intra-hemispheric (Equator-to-pole) insolation and temperature gradient.…”

“…We note that obliquity may also affect climate through other insolation gradients (e.g. Reichart, 1996;Leuschner and Sirocko, 2003;Raymo and Nisancioglu, 2003;Antico et al, 2010;Mantsis, 2011), which will be considered in the Discussion section (Sect. 4).…”

Cyclostratigraphy and its revolutionizing applications in the earth and planetary sciences

“…Intercalibration between the ATS and high-precision geochronology to estimate and reduce error is an ongoing activity. Computer modeling of Milankovitch-forced climate change has moved forward with new applications of sophisticated atmosphere-ocean general circulation models (e.g., Ashkenazy et al, 2010;Antico et al, 2010;Merlis et al, 2013aMerlis et al, , 2013b and Earth system models (e.g., Gallée et al, 1991Gallée et al, , 1992Cane et al, 2006;Braconnot et al, 2007aBraconnot et al, , 2007bGanopolski and Calov, 2012;Crucifi x, 2012).…”