2018 New York Laws
RPP - Real Property
Article 8 - Conveyances and Mortgages
240-C - Joint Tenancy Severance.

§ 240-c. Joint tenancy severance. 1. In addition to any other means by
  which a joint tenancy with right of survivorship may be severed, a joint
  tenant  may  unilaterally sever a joint tenancy in real property without
  consent of any non-severing joint tenant or tenants by:
(a) Execution and delivery of a deed that conveys legal title  to  the
  severing  joint  tenant's  interest  to  a  third person, whether or not
  pursuant to an agreement requiring the third person  to  reconvey  legal
  title to the severing joint tenant; or
(b)  Execution  of  a  written instrument that evidences the intent to
  sever the joint tenancy, including a deed that names the severing tenant
  as the direct grantee of the severing tenant's interest.
2. No severance of a joint tenancy pursuant to subdivision one of this
  section shall terminate the right of survivorship  of  any  non-severing
  joint  tenant or tenants as to the severing tenant's interest unless the
  deed or written instrument effecting the severance is recorded, prior to
  the death of the severing tenant, in the county where the real  property
  is located.
3. Nothing in this section shall limit the manner or effect of:
(a)  A  severance  of a joint tenancy pursuant to a written instrument
  executed by all joint tenants, or pursuant to a written agreement of all
  joint tenants.
(b) A severance of a joint tenancy effected by a  deed  from  a  joint
  tenant to another joint tenant.
(c) A severance ordered by a court of competent jurisdiction.