The waning weeks of the year, a time when some of us feel inclined to contemplate the world’s biggest issues, coincide in Atlanta with the final days of four shows that deal with immense questions of history and nature, through the making of uncommonly lovely works of art. At Jackson Fine Art through December 22, former Atlantan Meghann Riepenhoff’s Imprint presents exquisitely abstract photographic prints that are created through the direct exposure of chemically treated paper to sunlight and to water in one form or another — rainfall, waves on shorelines or snow. The cyanotype process allows Riepenhoff to document rapidly changing natural conditions with a medium that itself changes rapidly, remaining subject to slower change even after the print has been (relatively) fixed. The Littoral Drift series is created by immersing the lower portion of the paper in lapping waves, and sometimes in the sand of the shoreline as well. The consistent, solidly dark color of the print’s upper part represents the portion left exposed to air and light during the lower part’s documentation of the watery phenomena that each title describes precisely: A particularly striking example, Littoral Drift #1051 (Tower Beach, Hilton Head, SC 05.02.18. Three Waves, Buried in Sand, Sea Squirt) contains the complex evidence of water, sand and a sea creature briefly washed in with the tide. The prints in the Ecotone series document the intensity of the rainfall that created differing patterns as individual drops altered the chemistry of the paper.