Description: Indian Ocean surface circulation is an important part of the global ocean conveyor belt, and is connected via two important gateways including the Indonesian Throughflow, and the Agulha Leakage. Changes in the surface hydrography of the Indian Ocean may therefore impact on the global overturning circulation. Here we present oxygen-isotopes and magnesium/calcium ratios from planktic foraminifer Globigernoides ruber from core site U1476 to reconstruct sea surface salinity and sea surface temperature in the Mozambique Channel, Indian Ocean for the past 1.2Ma. We investigated the changes in the surface hydrography of the Mid-to-Late Pleistocene and find an early salinification and warming during glacial cycles.

Description: Indian Ocean surface circulation is an important part of the global ocean conveyor belt, and is connected via two important gateways including the Indonesian Throughflow, and the Agulha Leakage. Changes in the surface hydrography of the Indian Ocean may therefore impact on the global overturning circulation. Here we present spectral, and cross spectral analysis results which show that Indian Ocean surface salinity and temperature increased during glacial intensification, with a significant lag prior to deglaciations.

Description: The confidence intervals published here are supporting and complementing the spectral and cross spectral data under: doi:10.1594/PANGAEA.955738.

Description: During the past five million yrs, benthic d18O records indicate a large range of climates, from warmer than today during the Pliocene Warm Period to considerably colder during glacials. Antarctic ice cores have revealed Pleistocene glacial-interglacial CO2 variability of 60-100 ppm, while sea level fluctuations of typically 125 m are documented by proxy data. However, in the pre-ice core period, CO2 and sea level proxy data are scarce and there is disagreement between different proxies and different records of the same proxy. This hampers comprehensive understanding of the long-term relations between CO2, sea level and climate. Here, we drive a coupled climate-ice sheet model over the past five million years, inversely forced by a stacked benthic d18O record. We obtain continuous simulations of benthic d18O, sea level and CO2 that are mutually consistent. Our model shows CO2 concentrations of 300 to 470 ppm during the Early Pliocene. Furthermore, we simulate strong CO2 variability during the Pliocene and Early Pleistocene. These features are broadly supported by existing and new d11B-based proxy CO2 data, but less by alkenone-based records. The simulated concentrations and variations therein are larger than expected from global mean temperature changes. Our findings thus suggest a smaller Earth System Sensitivity than previously thought. This is explained by a more restricted role of land ice variability in the Pliocene. The largest uncertainty in our simulation arises from the mass balance formulation of East Antarctica, which governs the variability in sea level, but only modestly affects the modeled CO2 concentrations.

Description: This dataset explores the variability in glacial-interglacial surface hydrography in the western Indian Ocean across the middle to late Pleistocene. Here, we provide 1kyr resolution Mg/Ca-based sea surface temperatures and surface oxygen isotope ratios of seawater (ice volume corrected) as proxy for surface palaeo-salinity from surface dwelling foraminifera Globigerinoides ruber from International Ocean Discovery Program core site U1476 located in the Mozambique Channel, which we use in combination with other records to create Indian Ocean sea surface salinity and sea surface temperature stacks. The data show increases in sea surface temperature and salinity during glaciation, with maximum temperature and salinity occurring at glacial maxima, prior to global deglaciations as indicated by benthic oxygen isotopes, a proxy for global ice volume. Lead-lag analyses were conducted using cross-spectral analysis between sea surface temperatures, salinity, and benthic oxygen isotopes. In parallel, sea-to-land pixel ratios from the ANICE-SELEN model across the Indonesian Archipelago show changes in land surfacing in the Indonesian archipelago due to globally sinking sea levels. The increase in surface temperature and salinification at U1476 occurs at the same time as major land surfacing in the Indonesian Archipelago suggesting a mechanistical link between land surfacing due to global sea level lowering, and changes in Indian Ocean surface hydrography that appears to be a resulting reduction in the considerably fresher Indonesian throughflow entering the Indian Ocean.