Fig 1.
Five global environmental and climatic variables and mean coral-reef growth over the past 11,700 calibrated years before present (yr BP; 1950 Common Era [CE]), as reported through five major temperature-fluctuation events of the Holocene.
The ecological response of mean reef growth rates (mm/yr) (a) reef growth (mm/yr) is represented by a dark purple line [24]. The five global variables include: 1) radiative forcing of (b) total solar irradiance (TSI) represented by the yellow line [25], where the TSI anomaly is relative to 1365 W/m2; 2) two orbital parameters of (c) orbital forcing represented by the orange line of Earth’s axial obliquity (degrees) and the blue line of orbital precession, e × sin(ϖ), where e is the eccentricity, and ϖ is the longitude of perihelion, which is dimensionless because it is a product of two ratios; 3) the first atmospheric-composition variable of (d) carbon dioxide (CO2) in parts per million by volume (ppmv) represented by the green line [26]; 4) the second atmospheric-composition variable of (e) volcanic forcing (W/m2) calculated from the mean stratospheric aerosol optical depth represented by the black line [27]; and 5) (f) ice-rafted debris (% of lithic grains) represented by the blue line [28]. The five major temperature-fluctuation events of the Holocene depicted are: 1) the Holocene Thermal Maximum (HTM) (10,000–6,000 yr BP); [13], shaded in yellow, 2) the 8.2 ka yr BP cooling event (8,200–8,040 yr BP) [14], shaded in purple, 3) the 4.2 ka yr BP cooling event [4,500–3,900 yr BP [15]], shaded in blue, 4) the warm Medieval Climate Anomaly (MCA) (1,000–700 yr BP) [16], shaded in pink, and 5) the Little Ice Age (LIA) (600–100 yr BP) [16], shaded in light green. The nine Bond-cycle events [29] are dashed gray lines labeled from B0 to B8, where B0 is the most recent cycle.
Fig 2.
The location of 1,890 samples, dating back 11,700 calibrated years before present (yr BP; 1950 Common Era [CE]) through the Holocene from 291 sites across the Pacific, Indian, and Atlantic Oceans, colored by region.
The 15 regions (from left to right) include: 1) Hawaii in orange, 2) French Polynesia in light green, 3) the Caribbean in light brown, 4) Barbados in pink, 5) the eastern Pacific in dark gray, 6) South America in light blue, 7) the Red Sea in light purple, 8) the Persian (Arabian) Gulf in dark green, 9) the southwestern Indian Ocean in maroon, 10) the Indian Ocean in navy blue, 11) Asia in teal, 12) the Sunda Shelf in dark purple, 13) northwestern Australia in gold, 14) the central Pacific Ocean in red, and 15) eastern Australia in medium blue. The map was generated using world polygon data from the maps package [38] in R [39].
Fig 3.
Relationships between three fixed-effect variables and mean coral-reef growth rates (mm/yr) through the Holocene from 291 sites across the Pacific, Indian, and Atlantic Oceans, from 11,700 years before present (yr BP; 1950 Common Era [CE]), through the Holocene.
Where the rate of change in sea level is measured in mm/yr, the atmospheric-composition variable cumulative volcanic forcing (W/m2) is calculated from the mean stratospheric aerosol optical depth, and SST is the sea-surface temperature (°C). Each coefficient is shown with three horizontal bars representing 90%, 80%, and 50% credible intervals. Coefficients with strong positive effects (≥ 80% credible intervals) are shown in blue. Terms not credibly different from zero (dashed line) are shown in gray.
Fig 4.
A mixed-modeling approach using second-order random-walk analysis in the Bayesian Integrated Nested Laplace Approximation (INLA) to assess the relationship between mean coral-reef growth rates (mm/yr) and 3 variables through the Holocene from 291 sites across the Pacific, Indian, and Atlantic Oceans, from 11,700 calibrated years before present (yr BP; 1950 Common Era [CE]).
(a) the effect of mean age of the coral-core samples, where BP is defined as calibrated years before present (1950 CE) is represented by a black line, (b) the effect of carbon dioxide (CO2) concentrations in parts per million by volume (ppmv) is represented by a green line, (c) the effect of stacked percentage of ice-raft debris types (as a proxy for Bond cycles) is represented by a blue line. Positive effects indicate periods where mean growth rates were higher than expected, relative to the overall trend, whereas negative effects indicate mean growth rates were lower than expected. Note that the five major temperature-fluctuation events of the Holocene depicted in (a) are: 1) the Holocene Thermal Maximum (HTM) (10,000–6,000 yr BP) [13], shaded in yellow, 2) the 8.2 ka yr BP cooling event (8,200–8,040 yr BP) [14], shaded in purple, 3) the 4.2 ka yr BP cooling event (4,500–3,900 yr BP) [15], shaded in blue, 4) the warm Medieval Climate Anomaly (MCA) (1,000–700 yr BP) [16], shaded in pink, and 5) the Little Ice Age (LIA) (600–100 yr BP) [16], shaded in light green. Also note that the nine Bond-cycle events [29] are dashed gray lines, labeled from B0 to B8, where B0 is the most recent cycle.
Fig 5.
Partial dependency plots resulting from the deep-learning neural-network model show the relationships between mean growth rates (mm/yr) and 3 variables through the Holocene from 291 sites across the Pacific, Indian, and Atlantic Oceans, from 11,700 yr BP.
(a) sea-surface temperature (SST) (°C) represented by a purple line, (b) rate of change in sea level (mm/yr) represented by a maroon line, and (c) absolute latitude (°N or °S) over the past 11,700 years represented by a charcoal line. Histograms of the distribution for each variable are shown in panels (d) through (f).
Fig 6.
The location of 1,869 samples, dating back 11,700 years before present (YBP; 1950 Common Era [CE]) through the Holocene from 288 sites across the Pacific, Indian, and Atlantic Oceans, with locally estimated scatterplot smoothing (LOESS) mean coral-reef growth rates (mm/yr) (95% confidence interval), grouped in 14 regions globally.
The colored LOESS line in each of the 14 regional plots corresponds to the color of sites on the map. The remaining 21 samples in the dataset reside in Barbados and were excluded in this comparison because mean ages were limited to earlier than ~9,000 yr BP (S13 Fig in S1 File). The five major temperature-fluctuation events of the Holocene depicted are: 1) the Holocene Thermal Maximum (10,000–6,000 yr BP) [13], shaded in yellow, 2) the 8.2 ka yr BP cooling event (8,200–8,040 yr BP) [14], shaded in purple, 3) the 4.2 ka yr BP cooling event (4,500–3,900 yr BP) [15], shaded in blue, 4) the warm Medieval Climate Anomaly (1,000–700 yr BP) [16], shaded in pink, and 5) the Little Ice Age (600–100 yr BP) [16], shaded in light green. The map was generated using world polygon data from the maps [38] in R [39].