| Type |
Article |
| Date |
2007-08 |
| Language |
English |
| Author(s) |
Evans H. K.1, Hall I. R.1, Bianchi G. G.1, Oppo D. W.2 |
| Affiliation(s) |
1 : Univ Cardiff Wales, Sch Earth Ocean & Planetary Sci, Cardiff CF10 3YE, Wales.
2 : Woods Hole Oceanog Inst, Dept Geol & Geophys, Woods Hole, MA 02543 USA. |
| Source |
Paleoceanography (0883-8305) (Amer Geophysical Union), 2007-08 , Vol. 22 , N. 3/PA3209 , P. 1-14 |
| DOI |
10.1029/2006PA001409 |
| WOS© Times Cited |
20 |
| Keyword(s) |
sortable silt, Deep Western Boundary Current, marine isotope stage 5 |
| Abstract |
Records from Ocean Drilling Program Sites 1057 and 1059 (2584 m and 2985 m water depth, respectively) have been used to reconstruct the behavior of the Deep Western Boundary Current (DWBC) on the Blake Outer Ridge (BOR) from 130 to 60 kyr B. P. (marine isotope stage (MIS) 5 and the 5/4 transition). Site 1057 lies within Labrador Sea Water (LSW) but close to the present-day boundary with Lower North Atlantic Deep Water (LNADW), while Site 1059 lies within LNADW. High-resolution sortable silt mean ((SS) over bar) grain size and benthic delta C-13 records were obtained, and changes in the DWBC intensity and spatial variability were inferred. Comparisons are made with similar proxy records generated for the Holocene from equivalent depth cores on the BOR. During MIS 5e, (SS) over bar evidence at Site 1057 suggests slower relative flow speeds consistent with a weakening and a possible shoaling of the LSW-sourced shallower limb of the DWBC that occupies these depths today. In contrast, the paleocurrent record from the deeper site suggests that the fast flowing deep core of the DWBC was located close to its modern depth below 3500 m. During this interval the benthic delta C-13 suggests little chemical stratification of the water column and the presence of a near-uniform LNADW-dominated water mass. After similar to 111 kyr B. P. the (SS) over bar record at Site 1057 increases to reach values similar to Site 1059 for the rest of MIS 5. The strengthening of flow speeds at the shallow site may correspond to the initiation of Glacial North Atlantic Intermediate Water formation also suggested by a divergence in the benthic delta C-13 records with Site 1057 values increasing to similar to 1.2 parts per thousand. Coupled suborbital oscillations in DWBC flow variability and paleohydrography persisted throughout MIS 5. Comparison of these data with planktonic delta O-18 records from the sites and alkenone-derived sea surface temperature (SST) estimates from the nearby Bermuda Rise suggest a hitherto unrecognized degree of linkage between oscillations in subtropical North Atlantic SST and DWBC flow. |
| Full Text |
| File |
Pages |
Size |
Access |
| Publisher's official version |
14 |
1 MB |
Open access |
|
