"Proximity's heritage is in direct, data and digital. Reza's expertise in these areas, together with his global experience and deep knowledge of the adtech and performance media landscape make him the perfect candidate for the role," said Chris Thomas, chairman of Proximity Worldwide. "The fact that Reza knows the Proximity network is a bonus and I am delighted he has returned."

Chambers joins the agency from The Barbarian Group, where she served as head of account management, working with clients such as GE, Google, IBM, KIND and PepsiCo. Prior to The Barbarian Group, Chambers worked at J. Walter Thompson New York as global business director on the Google account. Before that, she also worked at 72andSunny, StrawberryFrog, Kirshenbaum, Bond & Partners and Goodby, Silverstein & Partners.

"Sherri has an incredible drive, a strategic mind and an understanding of the J. Walter Thompson New York culture," said Power. "Her knowledge of the agency combined with her breadth and expertise within the industry, makes her an invaluable asset."

Prior to that, she was executive creative director at BBDO Guerrero, where she created Pantene's "Labels for women," which earned multiple awards. Sanchez also co-created #Unselfie, which was created to raise awareness of the devastation in the Philippines after Typhoon Haiyan. The campaign garnered numerous awards, including two Cannes Lions.

"Tin is a true creative force, having led highly recognized, awarded, and effective work across a diverse range of accounts," said Shah. "As we look to deepen our storytelling abilities and invent new brand experiences for our clients, Tin is a thrilling addition to the New York leadership team."

Baehr rejoins Momentum following her role as senior vice president, head of strategy for Jack Morton NYC. While there, she was charged with re-invigorating the agency's positioning, philosophy and overall creative strategy offerings. Prior to that, Baehr was Momentum's North American strategic lead on Coca-Cola, working with McCann Worldgroup partners to help redefine the brand's global strategy.

"Abbie is a rare, bold talent in an industry that requires ever bolder ideas. Our industry is rapidly shifting its focus toward creating intimacy at scale for brands, and working to understand the behavioral, technological and societal shifts that are making such focus essential," said Klau. "Her proven capabilities in creating powerful human truths for both B2B and B2C brands will be a huge competitive advantage for Momentum clients."

Her former clients include Pepsi, Chevrolet, Cadillac, Reckitt Benckiser, Novartis, HBO, GE, AT&T, Target, Time Warner Cable, Colgate, Dove, Match.com and Airbnb.

"As executive creative director in New York and a member of our global creative council, Rachel will have an instrumental role in the creative direction of our agency," said Bruce Henderson, chief creative officer of Jack Morton Worldwide. "Rachel's creative vision, her breadth of experience, and her proven leadership skills will be invaluable as we continue to create extraordinary brand experiences for our clients."