It's the main dimension where Obito and Sakura operating inThe lava world and the world that Obito and Sakura were operating from. By opening a portal to the lava world, Naruto’s chakra presence seeped into that world (lava world) which was closer to Sasuke.
Either that or Sasuke felt the chakra from the RSM Naruto clone that Obito brought along with Sakura, which eventually got destroyed. Which explains why he felt it for a second. Which was the same world that Sakura and Obito were operating from.
I’m right either way but it’s definitely the first choice.
Also, how you believe so certainly that Lava Dimension is closer to the Ice Dimension?