Millennial‐scale sea surface temperature and Patagonian Ice Sheet changes off southernmost Chile (53°S) over the past ∼60 kyr

Abstract

[1] Glacial millennial-scale paleoceanographic changes in the Southeast Pacific and the adjacent Southern Ocean are poorly known due to the scarcity of well-dated and high resolution sediment records. Here we present new surface water records from sediment core MD07-3128 recovered at 53°S off the Pacific entrance of the Strait of Magellan. The alkenone-derived sea surface temperature (SST) record reveals a very strong warming of ca. 8°C over the last Termination and substantial millennial-scale variability in the glacial section largely consistent with our planktonic foraminifera oxygen isotope (d 18 O) record of Neogloboquadrina pachyderma (sin.). The timing and structure of the Termination and some of the millennial-scale SST fluctuations are very similar to those observed in the well-dated SST record from ODP Site 1233 (41°S) and the temperature record from Drowning Maud Land Antarctic ice core supporting the hemispheric-wide Antarctic timing of SST changes. However, differences in our new SST record are also found including a long-term warming trend over Marine Isotope Stage (MIS) 3 followed by a cooling toward the Last Glacial Maximum (LGM). We suggest that these differences reflect regional cooling related to the proximal location of the southern Patagonian Ice Sheet and related meltwater supply at least during the LGM consistent with the fact that no longer SST cooling trend is observed in ODP Site 1233 or any SST Chilean record. This proximal ice sheet location is documented by generally higher contents of ice rafted debris (IRD) and tetra-unsaturated alkenones, and a slight trend toward lighter planktonic d18 O during late MIS 3 and MIS 2.

Glacial reduction and millennial-scale variations in Drake Passage throughflow

“…S2) allow the investigation of CHC strength changes at millennial timescales as an approximation of the northern ACC fraction of DP throughflow. Previous work on this core revealed substantial fluctuations of sea surface temperatures (SSTs) that largely follow the timing of temperature fluctuations observed in Antarctic ice cores (19). The lower-resolved, radiocarbon-dated core MR0806-PC09 [age model updated from the work by Shiroya et al (21)] is used to complement glacial-interglacial ACC strength estimates directly within the northern sector of the DP.…”

“…The age model [updated from the work by Caniupán et al (19)] is well-constrained by radiocarbon dating, the occurrence of the Laschamp paleomagnetic excursion, and correlation to the well-dated sediment record from Ocean Drilling Program Site 1233 (20). High sedimentation rates during most of the glacial section (Fig.…”

The timing and cause of glacial advances in the southern mid-latitudes during the last glacial cycle based on a synthesis of exposure ages from Patagonia and New Zealand

“…In this interval, dust and IRD records show little change beyond occasional small peaks Caniupán et al, 2011;Figure 8K and L) and SSTs were equivalent to those during the Holocene (Barrows et al, 2007a). Antarctic temperatures warmed following MIS 4 (EPICA, 2006), and early MIS 3 showed a strong millennial-scale pattern of warming and cooling into and out of the A4-1 events (Blunier & Brook, 2001; Figure 8D).…”

“…Likewise, numerous SST reconstructions suggest that the decline towards peak glacial conditions had started by at least 30 ka in the south-eastern Pacific (Lamy et al, 2004;Kaiser et al, 2005;Lamy et al, 2007;Caniupán et al, 2011; Figure 8F and G), west of New Zealand and south of Australia (Pelejero et al, 2006;Barrows et al, 2007a;Calvo et al, 2007; Figure 8E), the Indian Ocean (Labeyrie et al, 1996), and the southeast Atlantic (Barker et al, 2009). A reconstruction from south of the Polar Front also shows a marked increase in Antarctic sea ice between ca.…”

Periodic 1.5 ka climate variations during MIS 2 in the belt of Southern Hemispheric westerlies

“…3e and f). The glacier dynamics of the SPI likely reflect climate variations because of shifts of the atmospheric circulation (Caniupán et al, 2011). Glacier advances were associated with the influence of the polar easterlies, whereas glacier retreats reflect intensified SHWs.…”