NOAA/WDS Paleoclimatology - Raymo 1992 DSDP Site 607 Isotope Data and Age Models

Deep sea δ18O records from benthic foraminifera provide a high-resolution overview of global ice volume changes over the last three million years, the interval typically referred to as the Northern Hemisphere Ice Ages. Prior to 2.7 Ma global climate appears to have been typically warmer than at present and the possibility of Antarctic deglaciation is suggested by depleted δ18O values observed prior to 2.9 Ma. Between 3.1 and 2.6 m.y., cold/warm oscillations are superimposed upon a gradual cooling trend which culminated with the growth of significant continental ice sheets in the northern hemisphere (equivalent to ~60m sea level change). Climate conditions during these cold extremes would be most analogous to late Pleistocene isotopic substages 5b and 5d. Since 2.7 Ma interglacial climate extremes have rarely been warmer than the Holocene. Significant 100 Kyr variance is observed during the late Pliocene interval and suggests that large ice sheets are not needed for climate to vary at the 100 Kyr eccentricity frequency. However, the rapid rates of climate change observed for late Pleistocene “terminations” are not typically observed earlier in the Plio-Pleistocene, although rates of ice decay are still usually faster than rates of ice growth. Fluctuations in North Atlantic Deep Water production (indicated by a δ13C gradient proxy) are not uniquely linked with climate transitions as indicated by δ18O and ice core CO2 records, implying that NADW production may be responding to factors other than global continental ice volume.

来自底栖有孔虫（benthic foraminifera）的深海氧同位素δ¹⁸O记录，为过去3百万年（通常被称为北半球冰期（Northern Hemisphere Ice Ages）的时段）的全球冰量变化提供了高分辨率的整体图景。
270万年前的全球气候整体较现代更为暖热，而290万年前观测到的贫化δ¹⁸O值，暗示了南极冰盖消融的可能性。
在3.1至2.6百万年期间，冷暖振荡叠加于逐渐变冷的趋势之上，该趋势最终以北半球大规模大陆冰盖的形成为顶点——这一过程对应约60米的海平面变化。
这些极寒时段的气候条件，与更新世晚期同位素亚阶段5b和5d最为相似。
自270万年前以来，间冰期的极端气候极少比全新世更为暖热。
上新世晚期时段存在显著的10万年周期变率，这表明即便不存在大规模冰盖，气候也可按照10万年轨道偏心率周期发生变化。
不过，更新世晚期“气候终止事件”中观测到的快速气候变化速率，在上新世-更新世早期并不常见——尽管冰消融速率通常仍快于冰生长速率。
北大西洋深层水（North Atlantic Deep Water, NADW）形成强度的波动（以碳同位素δ¹³C梯度代用指标表征），并不与δ¹⁸O及冰芯二氧化碳记录所指示的气候转型一一对应，这意味着NADW的形成可能受全球大陆冰量之外的其他因素调控。