Stable isotope record of foraminifera from sediment core EW9209-1JPC

Stable isotopic measurements of G. sacculifer and C. wuellerstorfi in a core from the western equatorial Atlantic imply that there are parallel, suborbital oscillations in surface water hydrography and deep water circulation occurring during oxygen isotope stages 2 and 3. Low values of G. sacculifer delta18O accompany high values of C. wuellerstorfi delta13C, linking warmer sea surface temperatures (SSTs) in the tropics with increased production of lower North Atlantic Deep Water (NADW). The amplitude of the delta18O oscillations is 0.6 per mil (or 2°-3°C), which is superimposed on a glacial/interglacial amplitude of about 2.1per mil. Using the G. sacculifer delta18O data, we calculate that surface waters were colder during stage 2 than calculated by CLIMAP [1976, 1981]. The longer-period (>2 kyr) oscillations in air temperature recorded in the Greenland and Antarctic ice cores appear to correlate with oscillations in sea surface temperature in the equatorial Atlantic. The magnitude of these oscillations in tropical SST is too large to have resulted from changes in meridional heat transport caused by the global conveyor alone. The apparent synchroneity of equatorial SST and polar air temperature changes, as well as the amplitude of the SST changes at the equator, are consistent with the climate effects expected from changes in the atmosphere's greenhouse gas content (H2Ovapor, CO2, and CH4).

对西赤道大西洋某岩芯中囊形拟抱球虫（G. sacculifer）与伍氏圆辐虫（C. wuellerstorfi）的稳定同位素测定结果显示，在氧同位素2期与3期期间，表层海水水文状况与深水环流均存在同步的亚轨道尺度振荡。囊形拟抱球虫的δ¹⁸O低值与伍氏圆辐虫的δ¹³C高值相伴出现，这表明热带海域更高的海表温度（SST）与北大西洋下层深水（NADW）生成量增加存在关联。δ¹⁸O振荡的幅度为0.6‰（对应温度变化2℃~3℃），该信号叠加于约2.1‰的冰期/间冰期幅度之上。基于囊形拟抱球虫的δ¹⁸O数据，我们计算得出，氧同位素2期的表层海水温度较CLIMAP[1976, 1981]的估算结果更低。格陵兰与南极冰芯中记录的更长周期（>2千年）气温振荡，似乎与赤道大西洋的海表温度振荡存在相关性。热带海表温度的这类振荡幅度极大，无法仅用全球输送带环流引起的经向热输送变化来解释。赤道海表温度与极地气温变化的表观同步性，以及赤道地区海表温度变化的幅度，均与大气温室气体含量（水蒸气、二氧化碳与甲烷）变化所预期的气候效应相符。