Smoke, ash from Australian bushfires 'caramelised' glaciers in South Island

Smoke and ash from the Australian bushfires have "caramelised" the normally pristine white Tasman Glacier this week.

Videos and photographs posted to social media show the impact the drifting smoke has had on the glaciers, with one user showing a photo of a helicopter resting high up in the mountains on a bed of ash-covered snow.

"Near Franz Josef glacier. The 'caramelised' snow is caused by dust from the bushfires. It was white yesterday," the tweet said.

South Islanders woke to an orange haze in the sky on Wednesday morning, and one social media user called the sight "apocalyptic".

Flight of the Conchords comedian Jemaine Clement tweeted a photo, showing the sun shrouded in smoke and giving off a "strange" colour.

"This was Dunedin, NZ at around 10.30 this morning. Photos don't do it justice, the light was orange with smoke from the Australian bushfires. If it's like this when there's an ocean and a few thousand km between us, the reality in Aus must be terrifying (sic)," a Twitter user said.

There were fears from an Australian climatologist the ash will make the glaciers recede more quickly, but local alpine guides said previous dustings were less spectacular and the glaciers always recovered.

"I don't think it'll cause any major issues for the glacier. It's been around for a long time, it'll be here for a long time to come," Fox Glacier Guiding CEO Rob Jewell said.

NIWA said only the fine ash particles have reached all the way across the Tasman, making air quality difficult to monitor accurately; but the haze may already be affecting the health of the million in New Zealand who suffer respiratory problems.

"The biggest recommendation we can make is to ensure people have their inhalers on them, and also to make sure they're not expired and they're not empty," Letitia Harding from the Asthma and Respiratory Foundation said.

Asthma experts say if the haze looks bad, asthmatics shouldn't go running or garden outside. They instead should stay inside and close the windows.

WeatherWatch forecasts the smoke will further thin out on Thursday as it moves over the North Island.