This month, the Tate Modern's third floor galleries (in which the museum's latest contemporary acquisitions are arranged, thematically) are chock full of Arte Povera works by Greek artist Jannis Kounnelis and small clusters of equally convention-bucking kids trundling through its daytime education programs. But just one level up, Roni Horn's first retrospective in the United Kingdom unfolds relatively quietly, in a manner not unlike that of slowly dipping one's head into a basin of fresh water. Surely, there is cause for contemplation here, and enough exhibition space -- thirteen galleries altogether -- to allow for plenty of time to linger, even to wallow in it.

In many ways, Horn is a difficult artist: She is overly theoretical but skeptical of the specific, both highly conceptual and yet very particular about material; she lusts after the geographical, and the meteorological, but is besotted with the liminal. Horn is a solipsist conflicted about her own self-prescribed androgynous identity. The show's title, "Roni Horn aka Roni Horn," hints at this (even if doing so a bit inelegantly).

Produced from the 1980s onwards, Horn's drawings -- collage-like blots of pigment applied to sometimes torn and (once again) diagrammatically pieced-together sheets of paper -- serve as strange cartographic artifacts of Horn's exceedingly careful process, previewing her later preoccupation with the mossy, variegated surface of Iceland as documented in her series of artist's books To Place. Not always compositionally exhilarating, her abstractly-plotted relations emphasize the relativity of form, their tirelessly penciled-in notations ultimately alluding to the fruitlessness of mapping. But there remains a palpable confidence in Horn's Sisyphean surrender to the exercise -- a certain delight in her inability to properly capture and record lived experience. Exhibition placards, which give space to the artist's expressed views of her own work in addition to dates and titles, describe her almost-pragmatic approach:

"The drawings are something I've carried on over decades, they are a kind of breathing activity on a daily level. Often these are images where you start off with two things, for example, and they're cut into one. Or you start out with two images cut into tight proximity. These are really drawings that are based in composing."

Horn is not so much interested in drawing, then, as she is in drawing out (temporally speaking). Several series of photographs tease out the ideas of perspective and perception that inform her drawings. For example: Her, Her, Her and Her (2002), which were taken in the labyrinthine interior of a Rekjavík women's locker room, or especially You are the Weather (1994-95), close-up portraits of a pale-faced woman emerging from a geothermal pool on the island of Iceland. It is not about subject -- about who the wet woman is (actually, artist Margrét Haraldsdóttir Blöndal) -- but rather how she is. And how one knows.

Paired objects -- another favorite trope -- are physically present in the copper cones of Things That Happen Again: For Two Rooms (1986), positioned at ever-so-slightly different angles in two back-to-back square rooms. Much can and has been made of the spatial coordinates of their placement and the identity crisis of doubling. New York Times critic Ken Johnson has characterized Horn's doubles as having no context, existing independently of any "other," and therefore persistently posing the question of vantage point: The viewer must struggle to find an indistinct position in relation to the pair. Also on display is the iconic, specter-like duo of Dead Owl (1998), an image that recurs again in some of Horn's later work. Horn's pairings become more complex when the repetition is structural rather than literal; as when the cycloramic series of Arctic Circle images, Pi (1998) -- a striking collection of photographs of Hildur and Bjorn Bjornson, interspersed with Eider nests, seascapes, and stills from the soap opera "Guiding Light" -- recalls the stainless steel sculpture Asphere (1988-2001). Both pieces are circuitous by nature, duping the viewer into a peculiar, seemingly logical loop even despite imperfect rounds.

Horn's images of the Thames constitute some of her best work. Clever and conceptual, these works chronice her Turner-like relationship to water in all of its complexity. Water is a suitable medium for Horn, after all; it is a physical entity, and yet can't be fully grasped. In a rectangular room overlooking the grey Thames, Horn's Still Water (1999) decidedly captivates in its earnesty and simple epistemological queries. The photographs, taken from a riverboat, show the surface of the water to be alternately quilted, soft, matte, referential, indeterminate, and probing. Fraught, often neurotic footnotes dotting the wide expanse of each image reflect upon and are finally washed into the river's run-away fate, from the anecdotal: "Alex's face reflected on eddies in A Clockwork Orange" to the Socratic: "When you say water, what do you mean?"

If Horn is accused of being dull, it may be because of her ability to articulate her own (often vague and abstract) ideas with clarity. That she works in geologic time, unwilling to bend to the ever-quickening flows of information makes for especially challenging viewing today. Like all minimal artists, Horn's grasp on the experiential aspect of her work is rigid; the curatorial hand of the artist is strictly felt. Still, her diverse body of work ebbs and flows, with new possibilities for perception at the surface level -- or just below it.

Roni Horn aka Roni Horn remains on view at the Tate Modern through May 25, 2009.

[Image credit: Roni Horn, You are the Weather 1994-95, courtesy the artist and Hauser & Wirth Zürich London © Roni Horn, gelatin-silver print, 64 C-prints and 36 gelatin-silver prints, 21.4 x 26.5 cm each, 100 units]