Whether the incompressible Euler equations in $R^3$ can develop a finite-time singularity from smooth initial data is a long-standing open problem in mathematical fluid mechanics. In the axisymmetric setting without swirl, global regularity is known for $C_c^\alpha$ initial vorticity for all $\alpha \geq 1/3$. Below this regularity threshold, for any $\alpha \in (0,1/3)$, we construct exact $C^\alpha$ self-similar blowup profiles for the vorticity of the 3D axisymmetric Euler without swirl, and build on them to prove asymptotically self-similar blowup from $C_c^\alpha$ initial vorticity and $C^{1,\alpha} \cap L^2$ initial velocity. Moreover, we provide a complete characterization of the limiting behavior of these $C^\alpha$ vorticity profiles and the associated blowup solutions as $\alpha$ tends to $1/3$. Our construction is based on lifting $C^\infty$ blowup profiles for a 1D nonlocal model and exploits the anisotropy of the 3D self-similar flow. To the best of our knowledge, our results provide the first example in which a singularity from a genuinely 1D nonlocal fluid model is lifted to construct blowup for incompressible fluid equations in $R^2$ or $R^3$.
