Table S2. Geochemical Data for the CAA-Rivers Project, collected from 2014 - 2016 18 2 Stn Ref Cl SO4 Ca Mg Na K Sr Ba δ O-H2O δ H-H2O Salinity DIC TA DOC Drainage Basin Bedrock Geology River Date Sampled Lat (°N) Lon (°E) 2 No. [µM] [µM] [µM] [µM] [µM] [µM] [nM] [nM] [‰] [‰] [PSS78] [μmol kg-1] [μmol kg-1] [mgC L-1] Area [km ] % Intrusive % Metamorphic % Sedimentary % Volcanic Akpat Kuunga a 1 8/11/2015 73.7638 -80.4468 101 166 269 154 93 6.3 418 165 -19.8 -148 0.06 526 512 0.2 96 0 13 87 0 Burnside River 25 8/13/2015 66.8414 -108.0421 31.1 23.1 66 50.4 45.7 10.5 77 34.3 -19.6 -156 177 2.9 24104 48 9 36 7 Charles York River 3 8/12/2015 73.7114 -82.7875 55.0 80.7 340 275 51.6 8.1 349 430 -20.4 -156 0.07 1092 1081 0.7 787 0 4 92 3 Coppermine (AVERAGE) b 16 2015-2016 Time Series 67.7633 -115.2538 33.8 23.8 245 179 46.2 13.6 124 143 -19.4 -163 0.05 826 821 4.0 51330 34 11 43 13 Creswell River 10 8/16/2015 72.8491 -93.4162 786 401 920 355 610 24.1 4200 214 -19.2 -150 0.16 1632 1637 1.0 1773 27 0 73 0 Cunningham River 7 8/13/2015 74.0153 -93.6242 152 188 880 201 118 8.9 1020 40.6 -19.4 -149 0.11 1752 1764 0.6 2155 0 0 100 0 Devon Island a 6 8/12/2015 74.5110 -88.4910 34.4 27.8 544 124 26.4 2.87 4470 174 -21.9 -167 0.07 1275 1285 0.5 1310 0 0 100 0 Ekalluk River 19 8/12/2014 69.4053 -106.3019 474 45.3 574 670 390 25.2 233 30.0 -19.1 -152 2.6 1916 0 0 100 0 Ellice River b 14 8/15/2015, 8/18/2015 67.8930 -104.0758 426 29.2 54.0 86 360 15.8 161 25.3 -18.5 -149 0.04 148 102 6.5 16938 53 45 1 1 Elu Inlet a 22 8/3/2014 68.5376 -105.6654 522 39.0 301 158 480 27.4 800 25.3 -17.5 -140 0.08 801 753 4.4 38 100 0 0 0 Freshwater Creek (AVERAGE) b 17 2014 - 2016 Time Series 69.1311 -104.9906 1040 99.5 497 640 750 26.4 228 53.4 -18.2 -149 4.9 1522 0 0 100 0 Garnier River 8 8/13/2015 73.9445 -92.0369 102 562 1040 251 123 12.3 1800 87 -21.0 -159 0.13 1502 1514 0.5 480 0 0 100 0 Glacier River a 2 8/11/2015 73.6124 -78.6805 20.6 34.2 61 22.7 84.4 11.3 104 39.3 -24.4 -185 0.02 192 187 0.3 983 44 38 17 1 Halokvik River b,d 20 8/6/2014, 8/24/2014, 8/27/2014 69.1762 -107.1083 171 58.3 436 558 121 11.8 109 46.4 -17.6 -143 4.3 n.d. n.d. n.d. n.d. n.d. Jayko River 18 9/3/2014 69.7388 -103.2630 775 101 532 680 570 23.1 217 30.6 -18.0 -145 3.4 1862 0 0 100 0 Koignuk River 23 8/3/2014 68.0994 -106.6921 454 28.2 120 120 390 20.3 235 19.7 -18.5 -149 0.05 9.5 889 27 18 0 55 Le Feuvre Inlet a 11 8/16/2015 72.3412 -96.9172 1160 170 920 429 1010 38.2 670 210 -18.3 -144 0.19 2252 2272 1.9 357 0 0 100 0 Marcil Creek 4 8/12/2015 72.9971 -84.9864 56.5 29.1 82 79 52.8 6.4 74 291 -21.4 -166 0.03 269 246 1.2 128 0 0 100 0 Mecham River 9 8/14/2015 74.6926 -94.7783 495 267 890 320 381 13.9 472 27.3 -17.7 -136 0.14 1710 1707 0.7 104 0 0 100 0 Pasley River 12 8/16/2015 70.4696 -95.5796 88.0 48.4 670 370 66.0 12.4 820 76 -18.5 -144 0.11 2011 2030 2.0 1214 0 0 100 0 Saaqu River 5 8/12/2015 73.7936 -86.9829 153 39.3 680 236 105 3.54 417 16.3 -20.2 -152 0.10 1681 1691 0.2 2220 0 0 100 0 Simpson River 13 8/17/2015 67.6763 -100.5683 1330 42.4 77 180 1070 33.6 309 17.9 -17.7 -144 0.09 196 159 5.5 7082 7 69 24 0 Tingmeak River 21 8/3/2014 68.2684 -104.9863 2810 124 153 424 2500 63 630 35.5 -18.0 -146 0.20 262 272 14.6 1189 31 69 0 0 Tree River b,c 15 08/01/2014, 8/19/2015 67.6242 -111.9161 468 49.1 226 250 413 16.3 169 260 -19.2 -153 0.12 769 745 3.2 5740 28 3 67 2 Western River 24 8/13/2015 66.3598 -107.1523 149 49.3 102 97 149 13.9 119 19.5 -19.5 -154 306 3.1 4226 5 19 74 2 Rain (Kugluktuk, NU) 16 8/25/2015 67.8276 -115.1016 6.3 1.3 11.3 4.8 3.3 1.1 7.7 3.7 -17.6 -137 Rain (Cambridge Bay, NU) 17 8/20/2016 69.12 -105.04 10.1 3.5 7.6 12.4 4.8 19.5 < d.l. 1.1 -13.9 -108 Ehoktok Lake 28 9/11/2015 67.4077 -102.7872 300 10.7 31.0 51.5 270 15.4 83 11.6 -18.6 -148 75.7 2.2 Ekalulia Lake (at Outflow) 30 8/15/2016 67.6500 -107.9641 1788 49.6 299 406 1511 59.8 419 256 -17.2 -136 Ferguson Lake 33 7/31/2014 69.4084 -104.9056 190 17.1 218 270 144 8.77 83 15.9 -18.4 -147 0.05 779 749 1.6 Greiner Lake System (Greiner Lake Inflow) 37 7/31/2014 69.2017 -104.8059 754 68.1 396 573 581 20.8 168 32.7 -18.5 -149 0.17 1451 1212 4.7 Greiner Lake System (Greiner Lake Outflow) 38 7/31/2014 69.1427 -104.9541 894 75.7 447 630 652 23.5 200 45.7 -18.7 -150 0.14 1427 1364 4.5 Greiner Lake System (Long Lake at Mount Pelly) 35 7/31/2014 69.1497 -104.6399 1110 78.3 509 697 731 27.1 219 36.0 -19.0 -151 0.16 1656 5.0 Greiner Lake System (Second Lake) 36 7/31/2014 69.1691 -104.6200 1205 103 595 916 982 32.3 239 42.0 -18.9 -151 6.0 Greiner Lake System (Upper Long Lake) 34 7/31/2014 69.0818 -104.4836 2300 192 1003 1384 1558 33.7 419 75.6 -17.4 -139 0.28 2829 2738 13.4 Lake in Upper Tree River 32 8/1/2014 67.3840 -112.1578 19.9 28.9 183 160 20.9 7.35 78 194 -19.3 -155 0.06 673 685 1.6 Small Lake North of Ehoktok Lake 29 9/11/2015 67.4965 -102.6977 2317 37.3 82.4 245 2001 38.6 316 34.4 -16.2 -134 243 4.2 Wentzel Lake 31 8/1/2014 67.8113 -110.4220 114 12.7 34.2 46.1 90.5 11.2 80 22.9 -18.7 -148 0.05 129 87.8 2.5 Lake ALLUVIAL WEATHERED BEDROCK OR GLACIOMARINE AND MARINE SEDIMENTS GLACIOFLUVIAL SEDIMENTS GLACIAL SEDIMENTS (TILL) BEDROCK Stn Ref % Glacier SEDIMENTS REGOLITH River Date Sampled Lat (°N) Lon (°E) Area No. Ice % Alluvial Sediments, % Littoral and Nearshore % Outwash Plain % Moraine % Regolith, % Bedrock, [%] % Offshore Sediments % Veneer % Ice-contact Sediments % Till veneer % Till Blanket % Regolith Veneer Undifferentiated Sediments Sediments Complex Undifferentiated Undifferentiated Akpat Kuunga a 1 8/11/2015 73.7638 -80.4468 0.1 45.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 54.4 0.0 0.0 0.0 0.0 Burnside River 25 8/13/2015 66.8414 -108.0421 14 0.0 0.0 0.0 0.0 0.0 0.0 0.0 53.9 2.5 0.0 0.0 0.0 43.7 Charles York River 3 8/12/2015 73.7114 -82.7875 0.0 10.6 0.0 0.0 0.0 0.0 0.0 0.0 30.6 0.0 0.0 0.0 0.0 58.8 Coppermine (AVERAGE) b 16 2015-2016 Time Series 67.7633 -115.2538 19 0.0 0.0 0.6 0.1 0.0 0.0 0.5 49.5 8.1 0.0 0.0 0.0 41.1 Creswell River 10 8/16/2015 72.8491 -93.4162 0.1 0.0 0.0 0.0 7.8 0.0 0.0 0.0 85.7 0.0 0.0 0.3 0.0 6.2 Cunningham River 7 8/13/2015 74.0153 -93.6242 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 10.1 0.0 0.0 77.0 0.0 12.9 Devon Island a 6 8/12/2015 74.5110 -88.4910 0.1 7.9 0.0 0.0 0.0 0.0 0.0 0.0 4.7 0.0 0.0 87.4 0.0 0.0 Ekalluk River 19 8/12/2014 69.4053 -106.3019 36 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0 0.0 0.0 Ellice River b 14 8/15/2015, 8/18/2015 67.8930 -104.0758 11 0.0 0.0 0.0 2.2 0.0 0.0 0.0 37.0 6.4 5.1 0.0 0.0 49.3 Elu Inlet a 22 8/3/2014 68.5376 -105.6654 15 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 100.0 Freshwater Creek (AVERAGE) b 17 2014 - 2016 Time Series 69.1311 -104.9906 22 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0 0.0 0.0 Garnier River 8 8/13/2015 73.9445 -92.0369 0.0 0.0 0.0 10.0 0.0 0.0 0.0 0.0 65.9 0.0 0.0 16.3 0.0 7.8 Glacier River a 2 8/11/2015 73.6124 -78.6805 0.8 83.2 0.0 0.0 0.0 0.0 0.0 0.0 0.3 11.2 0.0 0.0 0.0 5.3 Halokvik River b,d 20 8/6/2014, 8/24/2014, 8/27/2014 69.1762 -107.1083 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. Jayko River 18 9/3/2014 69.7388 -103.2630 23 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0 0.0 0.0 Koignuk River 23 8/3/2014 68.0994 -106.6921 16 0.0 0.0 0.0 0.0 0.0 0.0 0.0 36.7 0.0 0.0 0.0 0.0 63.3 Le Feuvre Inlet a 11 8/16/2015 72.3412 -96.9172 1.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 42.0 58.0 0.0 0.0 0.0 0.0 Marcil Creek 4 8/12/2015 72.9971 -84.9864 0.8 0.0 0.0 0.0 10.2 0.0 0.0 0.0 89.8 0.0 0.0 0.0 0.0 0.0 Mecham River 9 8/14/2015 74.6926 -94.7783 1.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9.9 0.0 31.3 58.8 0.0 Pasley River 12 8/16/2015 70.4696 -95.5796 1.4 0.0 0.0 0.1 0.0 0.0 16.6 0.0 17.4 65.9 0.0 0.0 0.0 0.0 Saaqu River 5 8/12/2015 73.7936 -86.9829 0.0 0.0 0.0 1.5 0.0 0.0 0.0 0.0 73.5 13.6 0.0 0.0 0.0 11.4 Simpson River 13 8/17/2015 67.6763 -100.5683 15 0.0 0.0 0.0 0.0 0.0 0.0 0.0 66.3 11.8 0.0 0.0 0.0 21.9 Tingmeak River 21 8/3/2014 68.2684 -104.9863 10 0.0 0.0 0.0 0.0 22.3 0.0 0.0 1.5 0.0 0.0 0.0 0.0 76.2 Tree River b,c 15 08/01/2014, 8/19/2015 67.6242 -111.9161 22 0.0 0.0 0.0 0.0 0.0 0.0 0.0 16.2 0.0 0.0 0.0 0.0 83.8 Western River 24 8/13/2015 66.3598 -107.1523 12 0.0 2.3 0.0 0.0 0.0 0.0 0.0 27.7 0.4 0.0 0.0 0.0 69.6 a - Rivers with no official name on available charts were named according to distinctive features of the region b - Reported values are averages from multiple visits (Ellice, Halokvik, Tree) or discharge weighted averages for timeseries observations (Table S3), except for Salinity, DIC, and TA, which were measured in August of each year, but not as part of the Coppermine River and Freshwater Creek time series. c - Samples collected as part of CAA-RP and GEOTRACES, Canadian Arctic GEOTRACES 2015 sampling location listed d - Three locations were sampled in August of 2014 at and around the 30-mile fish weir; weir location given