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We use global and local helioseismic inversions to explore the prevailingdynamical balances in the solar Near-Surface Shear Layer (NSSL). Thedifferential rotation and meridional circulation are intimately linked, with acommon origin in the turbulent stresses of the upper solar convection zone. Theexistence and structure of the NSSL cannot be attributed to the conservation ofangular momentum by solar surface convection, as is often supposed. Rather, theturbulent angular momentum transport accounts for the poleward meridional flowwhile the often overlooked meridional force balance maintains the mid-latituderotational shear. We suggest that the base of the NSSL is marked by atransition from baroclinic to turbulent stresses in the meridional plane whichsuppress Coriolis-induced circulations that would otherwise establish acylindrical rotation profile. The turbulent angular momentum transport must benon-diffusive and directed radially inward. Inferred mean flows are consistentwith the idea that turbulent convection tends to mix angular momentum but onlyif the mixing efficiency is inhomogeneous and/or anisotropic. The latitudinaland longitudinal components of the estimated turbulent transport are comparablein amplitude and about an order of magnitude larger than the verticalcomponent. We estimate that it requires 2--4% of the solar luminosity tomaintain the solar NSSL against the inertia of the mean flow. Most of thisenergy is associated with the turbulent transport of angular momentum out ofthe layer, with a spin-down time scale of $\sim$ 600 days. We also addressimplications of these results for numerical modeling of the NSSL.

Gyroscopic Pumping in the Solar Near-Surface Shear Layer