rank: NA

scope: climate

rank: NA

scope: climate

rank: NA

scope: climate

rank: NA

scope: climate

rank: NA

scope: climate

rank: NA

scope: climate

rank: NA

scope: climate

rank: NA

scope: climate

basis: ocean-atmosphere climate coupling acts to enhance the IOD-related climate signal captured by coral ?18O over that expected from SST anomalies alone

direction: decrease/increase

interpDirection: decrease/increase

scope: climate

variable: temperature

variableDetail: sea surface

variableGroup: temperature and salinity

scope: climate

scope: climate

basis: We found that the correlations with d18O are 0.72 (with total pseudocoral), 0.47 (with SST component), and 0.68 (with SSS component), p < 0.01 for all three (Figure S1), indicating that SSS changes represent a larger fraction of the variance in the coral d18Oanomaly signal than SST changes, as expected from the larger magnitude of interannual SSS variations at this site. Testing several different percent contributions of SSS and SST to create the pseudocoral, we determined that a combination of 35% SST and 65% SSS results in the closest representation to the observed coral d18Oanomaly values. This was calculated by creating a pseudocoral that consisted of percent SST/SSS contributions that ranged from 100/0% to 0/100%, in increments of 5% (i.e., 100/0, 95/5, 90/10a€¦ 5/95, 0/100). The pseudocoral consisting of 35/65% gave the highest correlation with the measured d18O time series, which provides the percent contributions of SST and SSS to the time series. This relationship was determined over the period 1970a€“2007, and is limited by the length of the instrumental SSS data set. We assume stationarity in the proportional contributions of SST and SSS to the coral d18O signal because SSS data needed to evaluate this assumption are lacking in the pre- 1970 period. However, the assumption of stationarity of a proxy-instrumental relationship developed over the instrumental time period affects all proxy-based climate reconstructions that extend beyond the instrumental period. Thus, lacking additional instrument data and/or another independent SST- or SSS-only proxy there is no easy way to reduce the uncertainty of the empirically derived proxy relationship over the calibration-verification interval.

direction: negative

inferredMaterial: seawater

integrationTime: 1

integrationTimeBasis: assigning the annual ?18O maximum to the month of the climatological SST minimum at both sites; linear interpolation between annual tie points and resampled to generate monthly series

integrationTimeUncertainty: 1/12-1/6

integrationTimeUncertaintyType: chronological

integrationTimeUnits: month

mathematicalRelation: linear

rank: 1

scope: isotope

seasonality: subannual

variable: temperature

variableGroup: Temperature

variableGroupDirection: negative

variableGroupOriginal: T_water

coefficient: NA

fraction: NA

basis: The annual range in coral ?18O is larger than expected based on SST alone, using published coral ?18O-SST dependencies of between 0.17??i¿½C?1 and 0.23??i¿½C?1 [Gagan et al., 2012]. Previous studies in the Mentawai Islands chain have shown that ocean-atmosphere climate coupling acts to enhance the IOD-related climate signal captured by coral ?18O over that expected from SST anomalies alone [Abram et al., 2007, 2008]. The sharp 18O enrichments that characterize the winter isotopic maximum in the South Pagai coral similarly support an additional and complementary rainfall modulation of the coral record during the IOD season.

inferredMaterial: seawater

integrationTime: 1

integrationTimeBasis: assigning the annual ?18O maximum to the month of the climatological SST minimum at both sites; linear interpolation between annual tie points and resampled to generate monthly series

integrationTimeUncertainty: 1/12-1/6

integrationTimeUncertaintyType: chronological

integrationTimeUnits: month

rank: 2

scope: isotope

variable: seawaterIsotope

variableGroup: EffectiveMoisture

variableGroupDirection: negative

variableGroupOriginal: d18O_seawater

coefficient: NA

fraction: NA

scope: isotope

coefficient: NA

fraction: NA

rank: NA