天文驱动的温室时期地下水储库与海平面变化

Astronomically forced changes in groundwater reservoirs and sea level during the greenhouse world

由全球变暖引起的海平面上升已经成为当前人类面临的核心挑战,迎接这一挑战的关键途径在于完善对温室地质时期全球海平面变化机制的理解.在无冰川活动的温室时期,海平面发生了频繁、大规模且快速的变化.然而,主流的冰川型海平面变化模型无法解释这一现象.大陆沉积物的潜在储层容量估算和大数据研究表明,温室时期的全球海平面变化可能与气候变化引起的大陆地下水活动有关.本文回顾了天文驱动的大陆地下水活动导致的海平面变化这一机制,提出了海绵大陆假说,认为天文因素驱动的气候变化使大陆含水层像海绵一样储水和排水,这可能是引起温室时期全球海平面和内陆湖平面大规模变化的机制之一.我们总结了近年来与深时海平面和湖平面重建有关的技术突破以及相关的温室时期研究实例,讨论了该方向亟待解决的问题,包括地下水的储量评估、研究手段及其储库的储水和排水机制等.

Sea level rise caused by global warming is one of the biggest challenges facing humankind.Deepening the understanding of the mechanism of global sea level change during the greenhouse period is the key to meeting this challenge.Large-scale,rapid sea-level changes frequently occurred during the greenhouse period lacking ice sheets.However,conventional sea level change models cannot explain this phenomenon,exposing their shortcomings.Estimation of global pore space in sediments and big data studies have indicated that global sea level changes may also be related to climate-related continental groundwater volume changes.We review the mechanism of sea level change caused by astronomically driven continental groundwater activities and propose a new Sponge Continent hypothesis:astronomical forcing drives climate change,causing filling and discharge of continental aquifers(by analogy,a sponge),which may in turn impact large-scale changes in global sea levels and inland lake level during the greenhouse period.We summarize recent technological breakthroughs related to the reconstruction of deep time sea-and lake-level changes.First,lake level change has been proposed as an indicator for the fluctuation of continental groundwater volume.Second,the sedimentary noise model and SediRate-Fischer method were proposed for the reconstruction of sea-and lake-level changes from sedimentary successions.Among these,the sedimentary noise model is developed based on the principle of the Milankovitch theory of climate change and time series analysis techniques.The noise model contains two complementary methods:dynamic noise after orbital tuning(DYNOT)and lag-1 autocorrelation coefficient(ρ1).The DYNOT method measures the noise intensity in paleoclimate time series,i.e.,the ratio of non-Milankovitch variation to total variation.By calculating the lag-1 autocorrelation coefficient of the target paleoclimate time series,theρ1 model can independently test the noise changes related to sea level variations.Theρ1 value decreases with the increase of noise intensity,and vice versa.The relative intensity of the sedimentary noise is anti-phased with the sea level change.When the sea level increases,the sedimentary noise decreases,and vice versa.This model can also be applied to the studies of lake level changes.Third,cyclo-magnetostratigraphy can provide a global synchronous stratigraphic correlation framework,which is vital for the evaluation of the aquifer eustasy and Sponge Continent hypothesis.The hypothesis of aquifer eustasy and Sponge Continent can be supported by geological evidence from the greenhouse period.This paper reviews recent progress related to astronomically forced sea level changes and/or lake level changes in chronological order.Some of them support the predicted antiphase relationship between the sea level curve and the contemptuous lake level curve as predicted by the Sponge Continent hypothesis.However,many unsolved issues about the nature and mechanisms of sea level change are to be explored.First,estimates of groundwater volume remain in dispute.Second,there is a lack of quantitative indicators for deep time groundwater variations.Third,the timing and mechanism of groundwater changes in continental aquifers are still unconstrained.Potential research directions are also discussed,including groundwater storage estimate,research methods,storage-drainage mechanism of groundwater reservoirs,etc.