Ancient Sea Level as Key to the Future
Ancient Sea Level as Key to the Future
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古代海平面是未来的关键
DOI：
10.5670/oceanog.2020.224
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发表时间：
2020
期刊：
影响因子：
2.8
通讯作者：
J. Wright
中科院分区：
文献类型：
--
作者：
K. Miller;John Schmelz;J. Browning;Robert E Kopp;G. Mountain;J. Wright
对古代海平面的研究有助于深入了解由于构造过程(例如，洋壳的产生)和气候变化(例如，地球轨道变化和大气二氧化碳引起的日照)引起的海平面变化的机制和速率。自中始新世(约4800万年前[Ma])以来，全球平均海平面(GMSL)的变化主要是由天文时间尺度(2400年、1200年、95/125年、41年和19/23000年[KYR])的冰量变化驱动的，受大气二氧化碳变化的调制。在高峰期(如始新世早期气候最佳时期56-48 Ma和晚白垩世早期约100-80 Ma)，大气中二氧化碳含量很高，地球温度升高5℃以上，大部分没有冰，仅冰层就贡献了约66m的GMSL上升。然而，即使在最温暖的时期(例如，始新世早期，约50 Ma)，小冰盖(相当于25米海平面)的增长和衰退也可能推动海平面变化，淹没大陆，控制浅水沉积的记录。冰盖在渐新世以前局限于南极内部，在34 Ma时首次到达南极海岸，最低海平面为现代GMSL-20±10m。在接近无冰的中新世气候最佳期(17-13.8 Ma)之后，在中新世(约13.8 Ma)形成了永久的东南极冰盖(EAIS)。在上新世(4-3 Ma)，二氧化碳与2020年CE(共同纪元)相似，海平面比现在高出约22±10m，需要格陵兰冰盖(海平面约7m)、南极西部冰盖(均衡补偿后约5m)和EAIS的脆弱部分显著丧失。始新世至上新世的北半球小冰盖在第四纪(过去255万年)扩展为大陆尺度。海平面在末次冰盛期(1950年前约27-20000年[ka])达到最低点(约130米)，在冰川消融(约20-11 ka)期间间歇性上升，速率有时超过47 mm yr-1(现代速率为3.2 mm yr-1)，并在全新世早期至中期从约11 ka至约4 ka逐渐减慢。在全新世晚期(包括CE4.2KYR)，GMSL只表现出±0.1m的百年变率。GMSL上升的现代事件始于19世纪末，20世纪上升的大部分可归因于全球变暖和冰川融化。在中等排放情景下，本世纪GMSL可能上升0.4-1.0米，古代的类比表明，较长期(百年至千年尺度)均衡上升约10米。在更高排放情景下，21世纪GMSL将上升超过2米，从长远来看，数十米不能被排除在外。
Studies of ancient sea levels provide insights into the mechanisms and rates of sea level changes due to tectonic processes (e.g., ocean crust production) and climatic variations (e.g., insolation due to Earth’s orbital changes and atmospheric CO2). Global mean sea level (GMSL) changes since the Middle Eocene (ca. 48 million years ago [Ma]) have been primarily driven by ice volume changes paced on astronomical timescales (2400, 1200, 95/125, 41, and 19/23 thousand years [kyr]), modulated by changes in atmospheric CO2. During peak warm intervals (e.g., Early Eocene Climatic Optimum 56–48 Ma and the early Late Cretaceous ca. 100–80 Ma), atmospheric CO2 was high and Earth was more than 5°C warmer and mostly ice-free, contributing ~66 m of GMSL rise from ice alone. However, even in the warmest times (e.g., Early Eocene, ca 50 Ma), growth and decay of small ice sheets (<25 m sea level equivalent) likely drove sea level changes that inundated continents and controlled the record of shallow-water deposits. Ice sheets were confined to the interior of Antarctica prior to the Oligocene and first reached the Antarctic coast at 34 Ma, with the lowest sea levels –20±10 m relative to modern GMSL. Following a near ice-free Miocene Climatic Optimum (17–13.8 Ma), a permanent East Antarctic Ice Sheet (EAIS) developed in the Middle Miocene (ca. 13.8 Ma). During the Pliocene (4–3 Ma), CO2 was similar to 2020 CE (Common Era) and sea levels stood ~22±10 m above present, requiring significant loss of the Greenland Ice Sheet (~7 m of sea level), West Antarctic Ice Sheet (~5 m after isostatic compensation), and vulnerable portions of the EAIS. The small Northern Hemisphere ice sheets of the Eocene to Pliocene expanded into continental scale in the Quaternary (past 2.55 million years). Sea level reached its lowest point (~130 m below present) during the Last Glacial Maximum (ca. 27–20 thousand years before 1950 [ka]), episodically rose during the deglaciation (ca. 20–11 ka) at rates that at times were in excess of 47 mm yr–1 (vs. modern rates of 3.2 mm yr–1), and progressively slowed during the Early to Middle Holocene from ca. 11 ka until ~4 ka. During the Late Holocene (last 4.2 kyr, including the CE), GMSL only exhibited multi-centennial variability of ±0.1 m. The modern episode of GMSL rise began in the late nineteenth century, with most of the twentieth century rise attributable to global warming and ice melt. Under moderate emissions scenarios, GMSL is likely to rise 0.4–1.0 m in this century, with ancient analogs suggesting a longer term (centennial to millennial scale) equilibrium rise of ~10 m. Under higher emissions scenarios, twenty-first century GMSL will rise greater than 2 m, and in the long term, tens of meters cannot be excluded.
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影响因子：
4
作者：
M. Willeit;A. Ganopolski;R. Calov;A. Robinson;M. Maslin
通讯作者：
M. Willeit;A. Ganopolski;R. Calov;A. Robinson;M. Maslin
DOI：
10.1073/pnas.1817205116
发表时间：
2019-06-04
影响因子：
11.1
作者：
Bamber, Jonathan L.;Oppenheimer, Michael;Cooke, Roger M.
通讯作者：
Cooke, Roger M.
影响因子：
5.3
作者：
Bertram, Rachel A.;Wilson, David J.;Riesselman, Christina R.
通讯作者：
Riesselman, Christina R.
影响因子：
2.8
作者：
Gasson E
通讯作者：
Gasson E