1511 / 2024-09-27 20:54:54

The Banda Sea: An example of tropical upwelling driving carbonate system changes during MIS 3 to 1

Indonesian Throughflow (ITF),B/Ca,SST,Carbonate system

Within the Indo-Pacific Warm Pool (IPWP) and Indonesian Throughflow (ITF) region, the Banda Sea is in a central position between the Indian and Pacific Oceans.Seasonal current reversals affect the intensity of upwelling and the surface hydrography, and on the glacial-interglacial timescale, by variations in sea level and water mass transport via the ITF. These factors directly and indirectly impact productivity, as indicated by alkenone and opal mass accumulation rates (MAR). During upwelling, intensified fixation of CO₂ in the mixed layer, and subsequent export of organic matter to and remineralization in deeper waters influence the carbonate system. We have investigated alkenone sea surface temperatures (SST), alkenone and opal MAR, and planktonic foraminiferal (Globigerinoides ruber) B/Ca from Site MD01-2380 in the Banda Sea. Our initial data encompass the time interval from 80 to 7 ka.

The amplitude of SST variations is 4.2 °C between extremes. Apart from the Holocene, local maxima are centred on 38 ka (Marine Isotope Stage [MIS] 3) and, somewhat unusual, 65 ka (MIS 4). Both alkenone and opal MAR correlate inversely with SST, suggesting that the latter are at least partially driven by changes in upwelling intensity.

B/Ca is considered an indicator of seawater carbonate saturation. We primarily use it to identify potential focal points for planned boron isotope analyses. There is little overall change before 8 ka, although variability is strongly reduced with the onset of Stage 2. There is no apparent similarity with either SST or productivity. The most prominent feature of the record is the steep rise from about 140 to 270 µmol/mol between 8 and 7 ka.