Nature | Vol 577 | 30 January 2020 | 661to cause the two-step reduction of the AMOC^17 (Fig. 1k). The simu-
lation successfully captured many aspects of the climate evolution
through T-I as recorded by proxy records^17 ,^20 ,^21. Subsurface warming
throughout much of the Atlantic basin was one of the responses to a
reduced AMOC^17 (Fig. 1k, l), supported by proxy temperature records
from intermediate-depth (1,000–1,500 m) North Atlantic core
sites^12.
We used the same climate model to conduct a transient simulation
that spans T-II and the LIG (140–115 ka) (Methods). We applied a FW forc-
ing consistent with reconstructions that reproduced the 7-kyr one-step
reduction in the AMOC suggested by proxy records of ocean circula-
tion (Extended Data Figs. 1 and 3) to quantify the associated changes
in subsurface temperatures during T-II and into the LIG and thus allow
a direct comparison with the subsurface warming simulated for T-I.
Figure 1 compares forcing of ice-sheet surface mass balance from
insolation, greenhouse gases (GHGs) and low-latitude Pacific sea sur-
face temperatures (SSTs) for T-II and T-I to representative examples of
the simulated oceanic forcing at sites in the North (45° N, 30° W) (Fig. 1e,
k) and South Atlantic (70° S, 45° W) (Fig. 1f, l). Changes in GHG concen-
trations and SSTs are similar during the two terminations, with increases
of ~2 W m−2 from GHGs and ~2 °C of warming from low-latitude Pacific
SSTs, which strongly influence Northern Hemisphere ice-sheet surface
mass balance^10. Despite these similarities, sea level reached modern
levels by the end of T-II, while it remained ~50% below modern levels at140138136134132130140138136134132130222018161412Age (ka)Age (ka) Age (ka)–3–2–1GHΔR
G (W m)–2ΔR
GH
G (W m)–2–2–101Temperature anomaly (°C)–120–80–40(^0) Sea level (m)
Depth (m) Depth (m)
Depth (m) Depth (m)
Sea level (m)
460
480
500
520
540
Insolation (W
–2m
)
Insolation (W
–2m
)
2220 1816 1412
Age (ka)
–120
–80
–40
0
460
480
500
520
540
–3
–2
–1
–2
–1
0
1
Temperature anomaly (°C)
4
8
12
16
20
AMOC transport (Sv) AMOC transport (Sv)
1,000
750
500
250
0
1,000
750
500
250
0
1,000
750
500
250
0
4
8
12
16
20
1,000
750
500
250
0
–1.50.50.54.56.5
–0.10.3 0.7 1.1 –0.10.3 0.7 1.1
a b c d e f
k
l
g
h
i
j
–1.50.50.54.56.5
Temperature (°C) Temperature (°C)
Temperature (°C) Temperature (°C)
Fig. 1 | Sea-level change and climate forcings during the penultimate (left)
and last (right) deglaciations. a, g, Eustatic sea-level record based on benthic
foraminifera isotopic records (blue line with 1σ uncertainty) (a) and in a
compilation of sea-level proxies shown by black dots with depth-range
uncertainties (g) (see Methods, Extended Data Figure 2). Also shown are RSL
records based on Red Sea isotopes (grey crosses) placed on a revised age
model, and U-series-dated corals in Tahiti (sky blue circles), Huon Peninsula
(light blue–green circles) and western Australia (blue circles) (Methods,
Extended Data Figure 2). All of the U-series ages have been recalculated and
normalized with the same set of decay constants for^234 U and^230 Th. Error bars
show 2σ age uncertainty. b, h, Insolation on 21 June for 65° N (data from ref. ^7 ).
c, i, Change in radiative forcing (R) from GHGs (CO 2 , CH 4 , and N 2 O)^6. The
uncertainty (shaded envelope) is the square root of the sum of squares of the
uncertainties of the individual GHGs. d, j, Tropical (23.5° N–23.5° S) mean
annual SST anomalies with 2 s.d. (shaded envelope) relative to the HadISST1.1
1870–1889 data^4 ,^5. e, k, Changes in the model maximum AMOC transport
(below 500 m; black line) and temperature (colour scale) as a function of time
and depth at 45° N, 30° W relative to 140 ka (e) and 22 ka (k)^17 as simulated by
NCAR CCSM3 (Methods). f, l, Evolution of temperature (colour scale) as a
function of time and depth at 70° S, 45° W relative to 140 ka (f) and 22 ka (l)^17 as
simulated by NCAR CCSM3 (Methods).
–50
–25
0
–50 Sea level (m)
–25
0
Sea level (m)
130128126124122120118
Age (ka)
–1
0
1
Temperature anomaly (°C) Temperature anomaly (°C)
–1.0
–0.5
0
0.5
1.0
450
475
500
525
550 Insolation (W
m–2
)
Insolation (W
m–2
)
10 86420
Age (ka)
Age (ka) Age (ka)
–1
0
1
450
475
500
525
550
–1.0
–0.5
0
0.5
1.0
1,000
750
500
250
0
Depth (m
)
1,000
750
500
250
0
1,000
750
500
250
0
Depth (m
)
1,000
750
500
250
0
Depth (m) Depth (m)
65° N
65° S
65° N 65° S
a b c d e f
k
l
g
h
i
j
ΔR
GH
(WG
m
–2)
ΔR
GH
(W mG
–2)
–0.1 1.1 –0.1 0.3 0.7 1.1
–1.50.52.54.56.5
Temperature (°C) Temperature (°C)
Temperature (°C) Temperature (°C)
–1.50.52.54.56.5
130128126124122120118 10 86420
0.3 0.7
Fig. 2 | Sea-level change and climate forcings during the last and present
interglaciations. a, g, Records of relative and global mean sea level (Methods,
Extended Data Fig. 2). The uncertainty (bars) on the coral data (circles) is 2σ.
b, h, Insolation on 21 June for 65° N (data from ref. ^7 ). c, i, Radiative forcing from
GHGs^6. The uncertainty is the square root of the sum of squares of the
uncertainties of the individual GHGs. d, j, Global mean annual SST anomalies
with 2 s.d. relative to the HadISST1.1 1870–1889 data^4 ,^5. e, k, Evolution of
temperature as a function of time and depth at 45° N, 30° W relative to 140 ka (e)
and 22 ka (k)^17 as simulated by NCAR CCSM3 (Methods). f, l, Evolution of
temperature as a function of time and depth at 70° S, 45° W relative to 140 ka (f)
and 22 ka (l)^17 as simulated by NCAR CCSM3 (Methods).