Asynchronous marine-terrestrial signals of the last deglacial warming in East Asia associated with low- and high-latitude climate changes

Abstract

A high-resolution multiproxy record, including pollen, foraminifera, and alkenone paleothermometry, obtained from a single core (DG9603) from the Okinawa Trough, East China Sea (ECS), provided unambiguous evidence for asynchronous climate change between the land and ocean over the past 40 ka. On land, the deglacial stage was characterized by rapid warming, as reflected by paleovegetation, and it began ca. 15 kaBP, consistent with the timing of the last deglacial warming in Greenland. However, sea surface temperature estimates from foraminifera and alkenone paleothermometry increased around 20-19 kaBP, as in the Western Pacific Warm Pool (WPWP). Sea surface temperatures in the Okinawa Trough were influenced mainly by heat transport from the tropical western Pacific Ocean by the Kuroshio Current, but the epicontinental vegetation of the ECS was influenced by atmospheric circulation linked to the northern high-latitude climate. Asynchronous terrestrial and marine signals of the last deglacial warming in East Asia were thus clearly related to ocean currents and atmospheric circulation. We argue that (i) early warming seawater of the WPWP, driven by low-latitude insolation and trade winds, moved northward via the Kuroshio Current and triggered marine warming along the ECS around 20-19 kaBP similar to that in the WPWP, and (ii) an almost complete shutdown of the Atlantic Meridional Overturning Circulation ca. 18-15 kaBP was associated with cold Heinrich stadial-1 and delayed terrestrial warming during the last deglacial warming until ca. 15 kaBP at northern high latitudes, and hence in East Asia. Terrestrial deglacial warming therefore lagged behind marine changes by ca. 3-4 ka.

Keywords: East Asian monsoon; asynchrony; land-sea correlation; low- and high-latitude interplay; thermohaline circulation.

Fig. 1.

Overview maps of the Antarctic Ocean, Pacific Ocean, and Arctic Ocean, as well as the adjacent East Asia, showing locations of core DG9603 and selected paleoclimate sites in relation to oceanographic features. (A) Shown are the following: Greenland ice core North Greenland Ice Core Project (NGRIP) (31), Hulu cave (29), Dongge cave (30), marine core MD97-2138 (35), marine core MD03-2611 (36), marine core ODP 1233 (37), Antarctic ice core Taldice (12). (B, Inset) Map of the ECS and Yellow Sea shows a sketch of regional oceanic and atmospheric circulation. The location of core DG9603 is shown in the Okinawa Trough. All positions of paleoclimate sites related to this study are shown in red stars.

Fig. 2.

Diagram of selected pollen types from core DG9603, together with δ¹⁸O records from the Greenland ice core (31) [on a GICC05 time scale (28)] and cave stalagmites (29, 30) of East Asia. Calibrated ages are shown by black dots with 1σ uncertainty on the left axis of the pollen diagram. Two blue-shaded bars show the YD and the cold period from ca. 26.5–15 kaBP, respectively. VPDB, Vienna Peedee Belemnite; VSMOW, Vienna Standard Mean Ocean Water.

Fig. 3.

Comparison of deglacial climate proxy records from core DG9603 with other proxy records for temperature and circulation in the Antarctic Ocean, Pacific Ocean, Greenland, and East Asia. δ¹⁸O record from the NGRIP (31) [on a GICC05 time scale (28)] (A), δ¹⁸O records from Hulu and Dongge caves (29, 30) (B), multiproxy records of core DG9603 in the dashed blue box [Castanopsis-Lithocarpus (C), Quercus E (D), PCA F1 (E), U^k′₃₇ SST (19, 20) (F), and FP-12E SSTw (18) (G)], Mg/Ca SST in MD97-2138 core (35) (H), U^k′₃₇ SST in MD03-2611 core (36) (I), U^k′₃₇ SST in ODP1233 core (37) (J), and δ¹⁸O record from Taldice (on a GICC05 time scale) (12) (K). Black dots at the bottom indicate dating control points with 1σ uncertainty for the DG9603 core. The yellow-shaded bar (arrow) and pink-shaded bar (arrow) show the timing of the last deglacial warming in SST records from the WPWP (H) and ECS (F and G), and in terrestrial climate records from East Asia (B–D) and Greenland (A), respectively; the blue-shaded bar shows the YD cold period. Red lines in F and G are 25-point running averages.