WINTER is coming for the art market.

Uncertainty caused by Britain’s prolonged attempt to split from the European Union, mass protests in Hong Kong, and the US-China trade war are weighing on collectors as the top auction houses gear up for their major year-end auctions. Their challenges are further complicated by the absence of works from big estates, such as the Rockefeller collection that brought in $835.1 million for Christie’s last year.

“I am not consigning a single thing to London sales at either Sotheby’s, Christie’s, or Phillips,” said Gabriela Palmieri, a New York art consultant. “My clients are nervous about Brexit.”

The geopolitical turmoil has caused disruptions in the global art trade, with currency fluctuations and new tariffs on Chinese art forcing buyers and sellers on other continents to recalibrate. A contraction in the “masterpiece market” of top works is primarily responsible for a first-half downturn this year. Through mid-September, a total of 14 works fetched at least $30 million, down from 23 such pieces during the same period in 2018. Aggregate sales for those works tumbled 38% to $781.8 million, according to an analysis of Artnet data.

The dearth of offerings from large estates, which generated more than $3 billion over the past three years, will make masterpieces harder to find this season and have the biggest impact on the marquee November sales in New York, according to dealers and advisers who said the auction houses are scrambling for property.

“What’s different this season is that the estates that have come to market haven’t included works of art that are $50 million to $100 million each,” said Marc Porter, Chairman of the Americas at Christie’s. “The most expensive objects are coming from discretionary sellers with whom we are still in negotiations.”

Sotheby’s, Christie’s, and Phillips “will have to get their sales lot-by-lot,” said Hugo Nathan, a London-based adviser. “It’s hard work and very expensive.”

Discerning buyers will be looking for distressed sales and to capitalize on currency fluctuations.

“The pound is cheap and there may be some opportunities,” said Wendy Cromwell, an art adviser in New York.

Collectors also will have plenty of options in the middle market as the slack at the high end doesn’t appear to be trickling down. Christie’s and Sotheby’s said they expect robust results from the contemporary art auctions in New York next week.

Estimates are down for key auctions in London and Hong Kong that will follow in the first week of October.

Sotheby’s is targeting sales of at least $336 million as it offers jewels, wines, watches, and fine art during five days of auctions in Hong Kong, a 16% drop from its low estimate for the same event in 2018. This year’s consignment period coincided with widespread protests that disrupted air travel.

Christie’s and Sotheby’s are similarly forecasting double-digit declines in London during Frieze Week, while smaller competitor Phillips, less dependent on collections and high-end properties, projects a 2% drop.

Sotheby’s evening auction of contemporary art on Oct. 3 is estimated to bring in at least £46 million ($57.5 million), with Jean-Michel Basquiat’s 1984 painting Pyro expected to fetch about £9 million. Bidding for a Banksy work depicting members of Parliament as chimpanzees could reach £2 million, which would be an auction record for the artist.

Christie’s top lot in London is also a Basquiat, Four Big from 1982, estimated at £7.5 million to £9.5 million. The company won the Jeremy Lancaster Collection, focused on contemporary British art, with 54 lots expected to bring in at least £13.8 million.

Demand is not the problem as long as the auction houses have quality material.

A case in point: Earlier in September in New York, Asia Week sales at Sotheby’s and Christie’s climbed from a year earlier as collectors and dealers competed for rare works from important collections, including those of the Metropolitan Museum of Art and the Art Institute of Chicago.

“Our collectors are impervious to shaky economic times,” said Cromwell, the New York art adviser. “When they find pictures they want, they show up.” — Bloomberg