Growth of the Maritime Continent and its possible contribution to recurring Ice Ages

Abstract

The areal extent of the Maritime Continent (the islands of Indonesia and surrounding region) has grown larger by~60% since 5 Ma. We argue that this growth might have altered global climate in two ways that would have contributed to making recurring Ice Ages possible. First, because rainfall over the islands of the Maritime Continent not only is heavier than that over the adjacent ocean but also correlates with the strength of the Walker Circulation, the growth of the Maritime Continent since 5 Ma may have contributed to the cooling of the eastern tropical Pacific since that time. Scaling relationships between the strength of the Walker Circulation and rainfall over the islands of the Maritime Continent and between sea surface temperature (SST) of the eastern tropical Pacific and the strength of easterly wind stress suggest that the increase in areal extent of islands would lead to a drop in that SST of 0.75°C. Although only a fraction of the 3-4°C decrease in SSTs between the eastern and western tropical Pacific, the growth of the Maritime Continent may have strengthened the Walker Circulation, increased the east-west temperature gradient across the Pacific and thereby enabled ice sheets to wax and wane over Canada since 3 Ma. Second, because the weathering of basaltic rock under warm, moist conditions extracts CO 2 from the atmosphere more rapidly than weathering of other rock or of basalt under cooler or drier conditions, the increase in weathering due to increasing area of basalt in the Maritime Continent may have drawn down enough CO 2 from the atmosphere to affect global temperatures. Simple calculations suggest that increased weathering of basalt might have lowered global temperatures by 0.25°C, possibly important for the overall cooling.

Active tectonic deformation along rejuvenated faults in tropical Borneo: Inferences obtained from tectono-geomorphic evaluation

“…Thus, results from our analysis could reveal that folding related to crustal shortening has occurred in the recent past (b 5 Ma) and could still be prevalent in the onshore fold and thrust belts of the Rajang Group Interior Highlands of Sarawak. Recent studies have confirmed that most of the high terrains in the islands of Southeast Asia are young (b 10 Ma) and mountain ranges have grown in the past 5 Ma (Molnar and Cronin, 2015), further confirming the results obtained by us.…”

Pliocene oceanic seaways and global climate

“…The constriction of the Indonesian Seaway with the related emergence of the Maritime Continent with a gain in landmasses of ~60% including many islands contributed to the general global cooling trend since ~5 Ma45. Intensified weathering of basaltic rocks along with the rising of the Maritime Continent might have contributed to a long-term CO 2 drawdown45.…”

“…Intensified weathering of basaltic rocks along with the rising of the Maritime Continent might have contributed to a long-term CO 2 drawdown45. Further, the slight tectonic-induced decrease of eastern tropical Pacific SST might have led to a stronger east-west Pacific SST gradient causing a stronger Walker circulation with far reaching climatic effects on North America45. The tectonic-induced distinct freshening of the subsurface eastern tropical Indian Ocean due to the restriction of the Indonesian Throughflow waters during ~3.5–2.95 Ma1315 (Fig.…”

“…Oceanographic changes as changes in AMOC variability, changes in temperatures and ocean currents are schematically indicated and based on the results of this study and other studies56789121314151617293243444546505152. IS = Indonesian Seaway, BS = Bering Strait.…”

Paleoclimate Constraints on Terrestrial Hydroclimate, Silicate Weathering, and the Carbon Cycle

“…For example, basaltic catchments weather faster than other silicates and account for approximately 20-35% of the modern global silicate weathering and CO2 consumption flux, while occupying less than 5% of sub-aerial continental area (Gíslason et al, 1996(Gíslason et al, , 2009 have been critically important in controlling past levels of atmospheric CO2 (pCO2) (Li and Elderfield, 2013;Kent and Muttoni, 2013;Molnar and Cronin, 2015;Jagoutz et al, 2016). However, scaling modern observations of weathering fluxes from catchments to both large spatial and temporal scales (e.g., Wallmann, 2001;Lefebvre et al, 2013;Li and Elderfield, 2013;Kent andMuttoni, 2008, 2013;Mills et al, 2014a;Li et al, 2016;Jagoutz et al, 2016;Cox et al, 2016) remains a challenge due to the lack of phenomenological modeling frameworks that predict weathering fluxes at both catchment and global scales under different climate states.…”