Planktic foraminifer-based sea-surface temperature reconstruction for sediment cores JM97-948/2A and MD95-2011 from the Vøring Plateau, eastern Norwegian Sea

The early to mid-Holocene thermal optimum is a well-known feature in a wide variety of paleoclimate archives from the Northern Hemisphere. Reconstructed summer temperature anomalies from across northern Europe show a clear maximum around 6000 years before present (6 ka). For the marine realm, Holocene trends in sea-surface temperature reconstructions for the North Atlantic and Norwegian Sea do not exhibit a consistent pattern of early to mid- Holocene warmth. Sea-surface temperature records based on alkenones and diatoms generally show the existence of a warm early to mid-Holocene optimum. In contrast, several foraminifer and radiolarian based temperature records from the North Atlantic and Norwegian Sea show a cool mid- Holocene anomaly and a trend towards warmer temperatures in the late Holocene. In this paper, we revisit the foraminifer record from the Vøring Plateau in the Norwegian Sea. We also compare this record with published foraminifer based temperature reconstructions from the North Atlantic and with modelled (CCSM3) upper ocean temperatures. Model results indicate that while the seasonal summer warming of the seasurface was stronger during the mid-Holocene, sub-surface depths experienced a cooling. This hydrographic setting can explain the discrepancies between the Holocene trends exhibited by phytoplankton and zooplankton based temperature proxy records.

Sea-surface temperature reconstruction of ODP Hole 175-1078C

A prominent feature in the Southeast Atlantic is the Angola-Benguela Front (ABF), the convergence between warm tropical and cold subtropical upwelled waters. At present, the sea-surface temperature (SST) gradient across the ABF and its position are influenced by the strength of southeasterly (SE) trade winds. Here, we present a record of changes in the ABF SST gradient over the last 25 kyr. Variations in this SST contrast indicate that periods of strengthened SE trade-wind intensity occurred during the Last Glacial Maximum, the Younger Dryas, and the Mid to Late Holocene, while Heinrich Event 1, the early part of the Bølling-Allerød, and the Early Holocene were periods of weakened SE trade-winds.

Sea surface temperature and salinity reconstruction of sediment core GeoB3129-1

A sediment core from the western tropical Atlantic covering the last 21,000 yr has been analysed for centennial scale reconstruction of sea surface temperature (SST) and ice volume-corrected oxygen isotopic composition of sea water (delta18O(ivc-sw)) using Mg / Ca and delta18O of the shallow dwelling planktonic foraminifer Globigerinoides ruber (white). At a period between 15.5 and 17.5 kyr BP, the Mg / Ca SST and delta18O(ivc-sw), a proxy for sea surface salinity (SSS), reveals a warming of around 2.5 °C along with an increase in salinity. A second period of pronounced warming and SSS increase occurred between 11.6 and 13.5 kyr BP. Within age model uncertainties, both warming intervals were synchronous with air temperature increase over Antarctica and ice retreat in the southern South Atlantic and terminated with abrupt centennial scale SSS decrease and slight SST cooling in conjunction with interglacial reactivation of the meridional overturning circulation (MOC). We suggest that during these warm intervals, production of saline and warm water of the North Brazil Current resulted in pronounced heat and salt accumulation, and was associated with warming in the southern Atlantic, southward displacement of the intertropical convergence zone and weakened MOC. At the termination of the Younger Dryas and Heinrich event 1, intensification of cross-equatorial heat and salt transport caused centennial scale cooling and freshening of the western tropical Atlantic surface water. This study shows that the western tropical Atlantic served as a heat and salt reservoir during deglaciation. The sudden release of accumulated heat and salt at the end of Younger Drays and Heinrich event 1 may have contributed to the rapid reinvigoration of the Atlantic MOC.

(Table 2) Paleoclimate reconstruction for palynology samples of Turkey

Palynofloras of the Kocaçay and Cumaovasi basins in western Turkey that belong to a time-span from the late Early to late Middle Miocene (the late Burdigalian-Serravallian) are studied and compared with published palynofloras of Europe and Turkey. Palynological data and numerical climatic results obtained by the coexistence approach indicate palaeoclimate changed from warm subtropical to temperate during the late Burdigalian-Serravallian. Moreover, the palaeoclimates of the Kocacay and Cumaovasi basins are compared with continental palaeoclimatic records of coal-bearing sediments in western Turkey and current temperatures in the Izmir region. According to this comparison, palaeoclimatic results of these basins and other localities in western Turkey show a distinct difference as a result of orographic change. The palaeovegetation in the Kocaçay and Cumaovasi basins during the studied time-span was affected by palaeotopography and palaeoclimate. In these basins mixed mesophytic, coniferous forests, and swamp palaeovegetation generally predominated during the late Early-early Middle Miocene. The role of the herbaceous taxa increased at the end of the late Middle Miocene (the Serravallian) in the Kocaçay and Cumaovasi basins. It is obvious from the palynomorph data of these basins that grassland palaeovegetation started to expand in the late Middle Miocene. Unlike in Central Europe, where late Burdigalian and Langhian represent a period of outstanding warmth, the so-called Mid-Miocene Climatic Optimum, cold month mean temperatures reconstructed in this study point to an ongoing cooling trend, already from the late Burdigalian onwards, possibly related to increasing terrestrial conditions in the study area.