>When I talk about oversampled networks in the U.S. and Europe, I’m referring to the densely populated regions, not northern Siberia …

OK. and yes - strictly speaking everything east of Ural mountains on the mainland is even not really anymore Europe. Novaya semlya seems to count as a kind of Ural extension.
But anyways I somehow imagine that one can have measurement stations also without inhabitants (?) and if there seems to be such a region with rather strong anomalies, one
would rather increase measurement points in order to find out what's going on, let it be arctic warming stream due to higher Albedo, volcanic activity due to tectonics, methane etc.
However it seems rather quite a few of stations either terminated service or stopped reporting to HADCRUT or HADCRUT stopped archiving. That is I meanwhile
found a textfile on HADCRUT with ALL stations collected by HADCRUT - unfortunately the most recent file offered is from 06/2011. It seems to hold quite some more russian stations than I had seen on Google earth.
From the file I extracted the first number of russian stations, which seem to be the stations in the high latitudes, check yourself how many terminated service before 2011:

Station: TIKHAYA BAY Rudolfa RUSSIA at 80.4, 52.9, measurement period: 19321995

Station: OSTROV VIZE--------- RUSSIA at 79.5, 76.9, measurement period: 19452011

Station: OSTROV GOLOMJANNYJ-- RUSSIA at 79.5, 90.6, measurement period: 19402011

Station: BARENCBURG---------- RUSSIA at 78, 14.2, measurement period: 19402008

Station: OSTROV UEDINENIJA RUSSIA at 77.5, 82.2, measurement period: 19351996

Station: RUSSKIY ISLAND------ RUSSIA at 77.1, 96.5, measurement period: 19352004

Station: GMO IM.E.K. FEDOROV- RUSSIA at 77.7, 104.3, measurement period: 19322011

Station: MYS ZELANIJA RUSSIA at 77, 68.6, measurement period: 19311996

Station: RUSSKAYA GAVAN RUSSIA at 76.2, 63.6, measurement period: 19321995

Station: TROYNOY ISLAND RUSSIA at 75.9, 83.3, measurement period: 19532004

Station: CAPE STERLEGOVA----- RUSSIA at 75.4, 88.9, measurement period: 19402011

Station: VILKICKOGO ISLAND RUSSIA at 73.5, 76, measurement period: 19542008

Station: IM. M.V. POPOVA----- RUSSIA at 73.3, 70, measurement period: 19402011

Station: DIKSON RUSSIA at 73.5, 80.1, measurement period: 19162011

Station: MALYE KARMAKULY----- RUSSIA at 72.3, 52.7, measurement period: 18762011

Station: LESKINO RUSSIA at 72.3, 79.5, measurement period: 19341994

Station: CAPE KHARASOVOY RUSSIA at 71.4, 67.6, measurement period: 19532004

Station: TAMBEY RUSSIA at 71.5, 71.8, measurement period: 19572011

Station: SOPOCHNAYA KARGA RUSSIA at 71.9, 82.7, measurement period: 19392004

Station: HATANGA RUSSIA at 72, 102.5, measurement period: 19062011

Station: CAPE BOLVANSKIJ----- RUSSIA at 70.4, 59, measurement period: 19592008

Station: GYDA RUSSIA at 70.9, 78.5, measurement period: 19482004

Station: SEJAHA RUSSIA at 70.2, 72.5, measurement period: 19572011

Station: VOLOCHANKA---------- RUSSIA at 70.9, 94.5, measurement period: 19332011

Station: ANDREYA ISLAND RUSSIA at 76.8, 110.8, measurement period: 19422004

Station: OSTROV KOTELNYJ----- RUSSIA at 76, 137.8, measurement period: 19332011

Station: OSTROV PREOBRAZENIJ RUSSIA at 74.7, 112.9, measurement period: 19341996

Station: SANNIKOVA STRAIT RUSSIA at 74.5, 140, measurement period: 19422008

Station: CAPE TERPAY-TUMUS--- RUSSIA at 73.5, 118.7, measurement period: 19611996

Station: DUNWAY ISLAND RUSSIA at 73.9, 124.6, measurement period: 19542008

Station: CAPE KIGILYAKH RUSSIA at 73.3, 139.9, measurement period: 19342008

Station: MYS SHALAUROVA------ RUSSIA at 73.1, 143.2, measurement period: 19282004

Station: SASKYLAH------------ RUSSIA at 71.9, 114, measurement period: 19352011

Station: TIKSI--------------- RUSSIA at 71.5, 128.9, measurement period: 19292008

Station: MOSTAKH ISLAND RUSSIA at 71.5, 129.9, measurement period: 19351999

Station: UEDEY Niznejansk RUSSIA at 71.5, 136.6, measurement period: 19612004

Station: RUSSKOYE USTYE RUSSIA at 71, 149, measurement period: 19552008

Station: DZALINDA------------ RUSSIA at 70.1, 113.9, measurement period: 19422011

Station: KJUSJUR------------- RUSSIA at 70.6, 127.4, measurement period: 19402011

Station: JUBILEJNAJA--------- RUSSIA at 70.7, 136.2, measurement period: 19612011

Station: CHOKURDAH RUSSIA at 70.6, 147.9, measurement period: 19392011

Station: ALAZEJA RIVER RUSSIA at 70.6, 154.2, measurement period: 19471997

Station: OSTROV CHETYR RUSSIA ASIA at 70.6, 162.5, measurement period: 19332011

Station: VALKARKAY RUSSIA at 70.1, 171, measurement period: 19412008

Station: OSTROV VRANGELJA RUSSIA at 71, 181.5, measurement period: 19262011

Station: SEVEROMORSK--------- RUSSIA at 69, 33.4, measurement period: 19362008

Station: TERIBERKA----------- RUSSIA at 69.2, 35.1, measurement period: 19142008

Station: KOLGUYEV ISLAND----- RUSSIA at 69, 49.2, measurement period: 19332008

Station: VIRTANIEMI---------- RUSSIA at 68.9, 28.4, measurement period: 19592008

Station: PADUN RUSSIA at 68.6, 31.9, measurement period: 19362008

Station: MURMANSK RUSSIA at 69, 33.1, measurement period: 19182011

Station: LOVOZERO RUSSIA at 68, 35, measurement period: 18992011

Station: GREMIKHA BAY ------ RUSSIA at 68, 39.5, measurement period: 19172008

Station: KANIN NOS----------- RUSSIA at 68.6, 43.3, measurement period: 19152011

Station: KOVDOR-------------- RUSSIA at 67.5, 30.4, measurement period: 19592008

Station: KANDALAKSA RUSSIA at 67.2, 32, measurement period: 19122011

Station: KRASNOSCELE--------- RUSSIA at 67.3, 37, measurement period: 19402011

Station: KANEVKA------------- RUSSIA at 67.1, 39.6, measurement period: 19592008

Station: SOJNA--------------- RUSSIA at 67.8, 44.1, measurement period: 19322008

Station: MYS MIKULKIN RUSSIA at 67.8, 46.7, measurement period: 19402008

Station: INDIGA-------------- RUSSIA at 67.6, 48.6, measurement period: 19232008