JOURNAL OF GEOPHYSICAL RESEARCH. M. R. Cape, Department of Physical Oceanography, Woods Hole

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1 JOURNAL OF GEOPHYSICAL RESEARCH Supporting Information for Foehn winds link climate-driven warming to ice shelf evolution in Antarctica M. R. Cape, 1,2 Maria Vernet, 1 Pedro Skvarca, 3 Sebastián Marinsek 4, Ted Scambos, 5 and E. Domack 6 Contents of this file Corresponding author: M. R. Cape, Department of Physical Oceanography, Woods Hole Oceanographic Institution, 266 Woods Hole Road MS-21, Woods Hole, MA 254, USA (mcape@whoi.edu) 1 Scripps Institution of Oceanography, University of California, San Diego, California, USA. 2 Woods Hole Oceanographic Institution, Falmouth, Massachusetts, USA. 3 Glaciarium, Museo del Hielo Patagó nico, El Calafate, Argentina. 4 Instituto Antárctico Argentino, Buenos Aires, Argentina. 5 National Snow and Ice Data Center, Boulder, Colorado, USA. August 19, 215, 9:5am

2 X Figures S1 to S9 Introduction This supporting information contains supplemental figures to the main article, primarily derived from the datasets and using the methods outlined in the methods section. References Grinsted, A., J. C. Moore, and S. Jevrejeva (24), Application of the cross wavelet transform and wavelet coherence to geophysical time series, Nonlinear Processes in Geophysics, 11 (5/6), , doi:1.5194/npg University of South Florida, St. Petersburg, Florida, USA. August 19, 215, 9:5am

3 X - 3 Temperature AWS ( C) N = 111 Int =.639 Slope = 1.2 r 2 =.9 Figure S Temperature manual ( C) Comparison between quality controlled AWS and manual (mercury thermometer) temperature measurements collected between December and March 24-25, 25-26, 26-27, and Reduced major axis regression was used to calculate regression statistics (top left). Red line indicates 1:1 correspondence. August 19, 215, 9:5am

4 X - 4 Figure S2. Image captured on March 26, 212 during the NBP12-3 cruise in the Larsen A embayment showing atmospheric patterns associated with a strong foehn event (see Figure 4). Cap clouds are visible over the mountains, with possible rotor clouds in the foreground and lenticular clouds above. Foehn clearance appears as a break in the clouds in the lee of the peninsula. Strong winds led to melting and advection of sea ice previously covering the embayment. August 19, 215, 9:5am

5 Figure S3. X-5 MODIS-Terra image collected on March 26, 212 at 13:55 UTC mapped as a) a true-color composite (MODIS bands 1, 4, 3 used as RGB components) and b) a false color composite (a combination of MODIS bands 3, 6, 7) used to distinguish snow and ice from clouds and water. In b), snow or ice-covered regions appear in dark red, with open water shown in black and cloud-covered regions in shades of white to orange-peach depending on the liquid water or ice content of the clouds. A coastal outline of the AP appears in black. Lenticular clouds are apparent over the peninsula as a long cloud bank extending from the tip of the peninsula to the southern reaches of the Larsen C, with orange-red regions along the AP signs of foehn clearance over the ridge of the mountain range. August 19, 215, 9:5am

6 X-6 Figure S4. AMPS forecast for March 26, 212 at 12: UTC, showing sea level pressure (blue isolines) across the Antarctic. Sea level pressure is not plotted over regions exceeding 5 m elevation. August 19, 215, 9:5am

7 Figure S5. X-7 AMPS forecast for March 26, 212 at 12: UTC, showing surface wind speed (m s 1 ). Only forecast data over the ocean and ice shelves is displayed. Narrow regions of high velocity winds are visible over the Larsen B embayment. August 19, 215, 9:5am

8 X a) DJF b) MAM c) JJA d) SON Std. Dev. Figure S Seasonal means of daily standard anomalies in ERA-Interim 5 hpa geopotential height computed for foehn days occurring during a) summer b) fall c) winter and d) spring. August 19, 215, 9:5am

9 X - 9 Figure S7. Wavelet power spectrum of the foehn anomaly time series between a) 1962 and 1972 and b) 1999 and 21. Colors indicate power. Shaded portion of the plots indicate the cone of influence, delimiting the region not influenced by edge effects. The continuous Morlet wavelet function was used in this analysis. More details on this method can be found in Grinsted et al. [24]. August 19, 215, 9:5am

10 X Foehn a) DJF b) NORTH c) Non foehn NORTH Foehn Non foehn 15% 1% 5% >= % 1% 5% >= d) MAM e) NORTH f) NORTH Relative frequency (%) % 1% 5% 15% 1% 5% >= g) JJA h) NORTH i) >= % 1%15% NORTH 5% 1%15% >= >= Figure S j) SON k) NORTH l) Temperature ( C) 15% 1% 5% >= NORTH 15% 1% 5% >= Same as Figure 9 for the Robertson Island (ROBN) weather station. Strong, southwesterly winds dominate atmospheric flow at this location under normal conditions. August 19, 215, 9:5am

11 X Temperature ( C) Month Figure S9. Monthly climatology of surface temperature at Matienzo between 1962 and 21. The horizontal black line represents mean conditions, with vertical bars corresponding to ±1 standard deviation about the mean. The red line indicates maximum recorded temperature during that month, and the blue line the minimum temperature. Temp ( C) Rel. hum. (%) Wind speed (m/s) Wind dir. ( ) 1 2 a) 3 1 b) c) d) July 211 FONP ROBN FLSK DUPT Figure S1. Same as Figure 4 (a-d) for a July 211 foehn event. August 19, 215, 9:5am

12 X - 12 Figure S11. Same as Figure 12 a-b for significance (p-value) of spatial correlation between monthly ice melt anomalies and monthly foehn frequency anomalies. Note low significance and correlation on the northeast portion of the SCAR Inlet ice shelf in Figure 11b and S9b is due to its retreat in 25. August 19, 215, 9:5am