Modelling the response of stable water isotopes in Greenland precipitation to orbital configurations of the previous interglacial

Figures & data

Fig. 1 (a) Monthly top of the atmosphere (TOA) shortwave radiation (SWR) [Wm⁻²] at 65°N for control run (ctrl), 115k, 122k and 126k calculated following Berger (1978). (b) TOA SWR anomalies at 65°N for Eemian time slices.

Table 1. Summary of boundary conditions for ECHAM4-iso simulations indicating source of sea surface temperature (SST), atmospheric CO₂ [ppmv], CH₄ [ppmv] and N₂O [ppbv] concentration, eccentricity (Ecc.) [°], obliquity (Obl.) [°], precession (Pre.) [o(ω−180°)], glacier mask (Glac.) and vegetation mask (Vege.)

Time slice	SST	CO2	CH4	N2O	Ecc.	Obl.	Pre.	Glac.	Vege.
Ctrl	IPSL_CM4 control	280	1.72	310	0.0167	23.4	102	Present	Present
115k	IPSL_CM4 115 kyr	280	1.72	310	0.0414	22.4	111	Present	Present
122k	IPSL_CM4 122 kyr	280	1.72	310	0.0407	23.2	356	Present	Present
126k	IPSL_CM4 126 kyr	280	1.72	310	0.0397	23.9	291	Present	Present

Fig. 2 Modelled JJA, DJF and annual mean 2m temperature (T_2m ) anomalies north of 45°N for the 115k time slice (a) to (c), 122k time slice (d) to (f) and the 126k time slice (g) to (i).

Table 2. Absolute and anomalous GIS annual mean surface temperature [°C], annual mean precipitation weighted δ ¹⁸O [‰] and annual mean precipitation amount [mm/yr] above 1500 m for control run and Eemian time slices

Experiment	T surf	δ ^18O	Precip.	T surf anomaly	δ ^18O anomaly	Precip. anomaly
Ctrl	−26.7±0.6	−27.3±1.0	210±34	N/A	N/A	N/A
115k	−27.4±0.9	−27.6±0.9	201±34	−0.7	−0.2	−10
122k	−26.7±0.9	−27.4±1.0	209±41	0.0	0.0	−2
126k	−25.7±0.9	−26.8±0.9	201±39	0.9	0.5	−10

Absolute values are listed±one standard deviation.

Fig. 3 Modelled JJA, DJF and annual mean precipitation weighted δ ¹⁸O anomalies north of 45°N for the 115k time slice (a) to (c), 122k time slice (d) to (f) and the 126k time slice (g) to (i).

Fig. 4 (a) Histogram of monthly 2m temperature (T_2m ) over Greenland above 1500 m for the control run (ctrl) during JJA (black) and DJF (grey). (b) Histogram of monthly δ ¹⁸O in precipitation over Greenland for the control run (ctrl) during JJA (black) and DJF (grey). (c) and (d) same as (a) and (b) but for the 126k time slice.

Table 3. Seasonal spatial slope (JJA and DJF means) and correlation (R ²) between δ ¹⁸O and temperature for land grid points north of 50°N (n=724) and for GIS above 1500 m (n=43)

Experiment	Slope >50°N (JJA)	Slope >50°N (DJF)	Slope of anomalies >50°N (JJA)	Slope of anomalies >50°N (DJF)	Slope GIS >1500 m (JJA)	Slope GIS >1500 m (DJF)
Ctrl	0.58±0.01 (0.92)	0.45±0.01 (0.78)	N/A	N/A	0.53±0.03 (0.91)	0.62±0.04 (0.87)
115k	0.58±0.01 (0.92)	0.46±0.01 (0.78)	1.14±0.07 (0.25)	0.51±0.02 (0.37)	0.56±0.04 (0.84)	0.61±0.04 (0.87)
122k	0.57±0.01 (0.90)	0.46±0.01 (0.78)	2.26±0.41 (0.04)	0.53±0.02 (0.48)	0.48±0.03 (0.90)	0.64±0.04 (0.87)
126k	0.58±0.01 (0.88)	0.46±0.01 (0.73)	0.48±0.06 (0.09)	0.65±0.02 (0.63)	0.50±0.03 (0.86)	0.55±0.04 (0.83)

Fig. 5 (a) Slope between annual mean precipitation weighted δ ¹⁸O and annual mean temperature (T_2m ) [‰/°C] calculated between the anomalies of the 115k, 122k and 126k time slices (b) one standard deviation on δ ¹⁸O–T_2m slope (c) linear correlation of δ ¹⁸O and T_2m between the time slices. (d) to (f) same as (a) to (c) but calculated using precipitation weighted annual mean T_2m . The asterisk mark the ice core drill sites listed in Table 4 [Camp Century (C), NEEM (N), NorthGRIP (NG), GRIP (G), Renland (R) Dye-3 (D3)].

Table 4.  δ ¹⁸O–temperature slope between Eemian time slices (115k, 122k, 126k) for ice core drill sites where Eemian ice has been recovered

Site	JJA [‰/°C]	DJF [‰/°C]	Annual [‰/°C]	Pre. w. annual [‰/°C]
Camp century	0.08±0.04 (0.52)	0.04±0.08 (0.09)	0.04±0.02 (0.02)	0.11±0.09 (0.33)
NEEM	0.07±0.05 (0.32)	0.56±0.04 (0.99)	0.35±0.12 (0.74)	0.14±0.04 (0.79)
NGRIP	0.29±0.08 (0.82)	8.27±41.59 (0.01)	0.61±0.04 (0.98)	0.26±0.00 (1.00)
GRIP	0.47±0.04 (0.98)	−0.08±0.02 (0.88)	1.08±0.33 (0.78)	0.41±0.03 (0.98)
Renland	0.23±0.01 (0.99)	1.86±0.13 (0.99)	0.55±0.11 (0.89)	0.86±0.06 (0.98)
Dye-3	0.25±0.10 (0.70)	1.35±0.64 (0.60)	−0.45±0.12 (0.82)	−0.15±0.09 (0.46)

The slope is listed for JJA and DJF means, annual mean precipitation weighted δ ¹⁸O with annual mean 2m temperature (Annual) and annual mean precipitation weighted δ ¹⁸O with annual mean precipitation weighted 2m temperature (Pre. w. annual). R ² listed in parenthesis. The ice core drill sites are marked in Fig. 5.

Fig. 6 (a) Specific humidity [kg/kg] of the 850 mb pressure level (shading) and vertically integrated vapour transport [kg/kg m/s] (arrows) for the control run (ctrl). (b) same as (a), but for the 126 kyr time slice (126k). (c) as in (b) but anomalies relative to the control run (126k-ctrl). Note the different scaling of the arrows showing the vapour advection. For vapour advection, only data for every second grid point are plotted.

Fig. 7 (a) δ ¹⁸O of vapour [‰] for the 850 mb pressure level (shading) and vertically integrated vapour transport [kg/kg m/s] (arrows) for the control run (ctrl) (b) same as (a), but for the 126 kyr time slice (126k). (c) as in (b) but anomalies relative to the control run (126k-ctrl). The vapour advection plotted in this figure is the same as in Fig. 6.

Fig. 8 (a) and (d) seasonal continental and oceanic evaporation fluxes relative to the control run, as well as the ratio of continental evaporation (Con. ratio) relative to total evaporation of the three regions. (b) and (e) seasonal δ ¹⁸O of evaporation fluxes [‰]. (c) and (f) seasonal anomalies in δ ¹⁸O of evaporation fluxes [‰]. The regions are defined as: North American (Con.) (land grid points 25°N <lat <70°N, 55°W <lon <170°W), North Atlantic (Marine) (ocean grid points 20°N <lat <60°N, 0°W <lon <95°W) and Arctic (Arctic) (ocean grid points lat >60°N) region. Bars represent fluxes for the different time slices: ctrl (grey), 115k (blue), 122k (green) and 126k (red).

Table 5. Ice core and modelled δ ¹⁸O for present (model: ctrl), the Eemian (model: 126k) and the Eemian anomaly (model: 126k-ctrl)

Drill site	Ice core (ic) Present (P ic )	Eemian (E ic )	E ic -P ic	Modelled (mo) Present (P mo )	Eemian (E mo )	E mo -P mo	ΔElev.
Camp Century	−29.5	−27.0	2.5	−21.8	−22.0	−0.2	−480
Dye-3	−27.6	−22.9	4.7	−21.5	−21.9	−0.4	−910
GISP2	−35.0	−32.3	2.7	−33.5	−33.0	0.5	−390
GRIP	−35.1	−31.6	3.5	−33.7	−32.9	0.8	−480
NEEM	−35.0	−31.4	3.6	−27.3	−26.5	0.7	−520
NGRIP	−35.4	−32.3	3.1	−31.7	−31.2	0.5	−460
Renland	−27.3	−23.8	3.5	−21.0	−20.3	0.7	−500

See Johnsen and Vinther (2007) and Dahl-Jensen et al. (2013) for ice core data. The last column on the right lists the estimate of how much lower (ΔElev. [m]) the ice sheet was at each site during the Eemian. The calculation of ΔElev. is based on a modelled δ ¹⁸O lapse rate of −0.56‰/100 m for the 126k time slice and the difference between columns E _ic -P _ic and E _mo -P _mo .

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