Michael Randropp stands on the edge of platform one at the railway station of Copenhagen's Kastrup airport and grimaces as he points toward the chest-high metal fence separating the tracks carrying trains between the Danish capital and Sweden.

"Commuters are calling this the new Iron Curtain, or Berlin Wall," he said.

The fence is designed to stop undocumented migrants from slipping across the rail tracks to avoid detection at this, the last station before Sweden.

Randropp, as chairman of the Commuters Association, represents the 15,000 people who shuttle daily between Copenhagen and Skane, the southern Swedish county encompassing Malmo, Sweden's third largest city, and Lund, home to one of the region's most prominent universities.

He believes the new measures insisted upon by the social democrat-led Swedish government will have a deleterious impact on the Oresund region, which has been evolving into a Scandinavian Silicon Valley.

New time-consuming identity checks at Kastrup station will add an estimated 45 minutes to the previous 36-minute trip for commuters heading back home to Malmo from work in Copenhagen. All train passengers heading to Sweden from Denmark will be required to disembark at the airport stop and have their papers examined by security guards, before being allowed to catch another train northwards.

Bridge too far?

The measures are designed to prevent undocumented migrants from slipping across the Oresund Bridge, which carries both vehicles and rail traffic between the two countries. Sweden has warned travel companies, such as the Danish train operator DSB, that they will be subjected to heavy fines if they allow "irregular" passengers to venture past the border.

The imposition of the new rules represents a substantial U-turn in policy from a country that for much of 2015 had trumpeted its open-door policy towards the stream of refugees and migrants crossing from Turkey to the Greek islands and heading northwards.

Sweden had expected to accept about 100,000 newcomers in 2015, but by year's end the figure was almost twice that, and the country was struggling to provide shelter, education and other essential services for would-be asylum seekers.

After failing to convince many other European nations - especially its neighbor Denmark - to shoulder some of Sweden's migrant burden - Prime Minister Stefan Lofven said in November that the country's generosity had been "naive."

Thousands of people allowed into the country disappeared after registration, causing the police and intelligence services to warn the government of a potential risk to state security.

"Perhaps it has been hard for us to accept that in our midst there are people sympathizing with the ISIS killers," said Lofven, using an alternative acronym to refer to the self-proclaimed "Islamic State" extremist group that has seized territory across Syria and Iraq and committed widespread atrocities, including terror attacks much farther afield.

According to Sweden's migration board, 80 percent of people seeking asylum in 2015 did not have a passport and 60 percent have still not managed to show any official identification papers to the authorities.

Snowball effect

Denmark's center-right Prime Minister Lars Lokke Rasmussen, who has presided over stringent new measures designed to make his country less attractive to migrants, is angry with Sweden's move, as he fears it will lead to more refugees seeking asylum in Denmark.

He also worries it will imperil years of investment in the Oresund region.

"It is a very unfortunate situation," said Rasmussen. "We have spent billions on building infrastructure up in the Oresund region. We have spent millions branding Copenhagen and Malmo as a single metropolitan area."

Rasmussen is under severe pressure from the anti-immigrant Danish People's Party (DPP), which provides essential parliamentary support. The DPP wants Denmark to have border controls and believes that the Schengen agreement, which is supposed to ensure free movement of people and goods throughout most of the European Union plus a handful of non-EU states, is effectively dead.

Rasmussen resisted this pressure when Sweden started doing passport checks on its side of the Oresund Strait in November, but is ready to reciprocate if the number of asylum seekers swells. This would mean reconstituting barriers between Germany and Denmark, as well as with Sweden.

Speaking to the Danish newspaper "Kristeligt Dagblad," migration researcher Joakim Ruist of Gothenburg University in western Sweden said, "I think the Swedish control will set a snowball effect in time, where countries quickly follow."

"Although it becomes uncomfortable and maybe just feels wrong, it can become the decisive step for a new political model of asylum in Europe and ultimately create a more humane treatment of refugees."

Ruist says the new measures will "provide a safer escape route," provide better treatment by closing borders and "instead distributes the people from camps in neighboring regions."

Incarceration for Syrians?

But another researcher, Lisa Pelling from the left-wing Swedish think tank Arena Idea, told "Kristeligt Dagblad" that Sweden's ID checks could trap Syrian refugees inside the war zone.

"The implication in the short term is that the EU's borders will shut as dominoes. Germany and Denmark will close. It will continue all the way to Greece, and finally, I am convinced that Turkey will also shut. It will end up keeping people incarcerated in Syria and will aggravate the carnage, because people can not get away," she said.

As Europe struggles to cope with the biggest movement of people since World War II, some Scandinavians are irritated that, for the first time in 53 years, since the signing of the Helsinki Treaty that was designed to boost travel and economic growth amongst the Nordic countries, they need to show passports to travel between Denmark and Sweden.

Crossing the Oresund Bridge on one of the last trains to Malmo before the new measures came into force was Ture Ertmann, a Dane who has lived in Sweden for 20 years. Ertmann, chief of staff for a Denmark-based shoe company, is concerned about the impact on business as commuters consider their options.

"At the moment we're wondering whether we should continue to stay living in Malmo in Sweden or move to Denmark," he told DW. "We have kids to pick up after school and shopping to do. How's that going to work, if it all takes an hour extra?

"There's no doubt this is a great challenge to the Schengen cooperation in Europe. The whole idea is that we're supposed to have external borders and now that whole system is breaking down. And every country is raising its inner borders. The whole cooperation across borders is challenged and I think that's worrisome."