The programme, which features two teams of celebrities competing to reach the freezing North Cape in Norway, averaged 2.86m (12.2%) on ITV1 from 9pm and 113k (0.5%) on ITV1 HD.
However, that was down 1.71m and 141k respectively on the show's debut episode on Saturday.
71 Degrees North was also beaten in the 9pm hour by factual entertainment series The Young Ones, which mustered 3.76m (16.1%) on BBC One.
New Who Wants To Be A Millionaire? appealed to 3.26m (13.8%) on ITV1 in the 8pm hour, but it was outperformed by Holby City, which took 5.29m (22.4%) on BBC One.
The One Show averaged 4.2m (20.8%) on BBC One from 7pm, up 600k week-on-week, while Grimefighters pulled in 2.19m (9.7%) on ITV1 from 7.30pm
On Channel 4, the second part of This Is England '86 appealed to 1.88m (11%) from 10pm, down 780k week-on-week. A further 329k (3.8%) watched the drama on Channel 4 +1.
Earlier on the channel, Celebrity Come Dine With Me brought in 1.6m (6.8%) in the 8pm hour and 318k (1.4%) on timeshift. New series Ramsey's Best Restaurant grabbed 1.56m (6.7%) from 9pm and 285k (1.6%) on Channel 4 +1.
Coast appealed to 2.24m (10.5%) on BBC Two in the 7pm hour, before factual entertainment series The Great British Bake Off took 2.74m (11.6%). Battle Of Britain drama First Light mustered 2.61m (11.5%) on the channel between 9pm and 10.30pm.
New series How To Take Stunning Pictures pulled in 543k (2.4%) on Five from 7.30pm, before Natureshock: Deadly Rat Invasion took 1.41m (6%). CSI: Miami and CSI: NY grabbed respective audiences of 2.07m (8.9%) and 1.56m (8.6%) on the channel from 9pm.
Overall, BBC One dominated primetime with 21.6% against ITV1's 13.6% (HD: 0.3%). BBC Two came in third with 10.4%, followed by Channel 4 with 6.6% (+1: 0.9%) and Five with 6.2%.
BARB ratings data supplied by Attentional