The shelf regions of West Antarctica are natural iron (Fe) fertilization zones where primary production greatly exceeds that of the adjacent broader Southern Ocean, where productivity is largely limited by the availability of this important micronutrient. These regions are currently experiencing rapid climate change driven by warming rates that are up to six times the global mean, resulting in system-wide changes, from physics to penguins. While it has long been assumed that continental sources of Fe are responsible for the high productivity in these regions, trace metal measurements to substantiate this claim and provide details on mechanisms have been few, until recently. This talk will summarize findings from seven cruises to the Amundsen Sea Polynya (ASP) and the Western Antarctic Peninsula (WAP) over the past few years. I will show evidence that these two regions have different modes of Fe delivery that help to structure distinct summertime phytoplankton blooms. Surprisingly, however, phytoplankton in both the ASP and WAP show evidence of mid-summer Fe stress, over large areas of the shelf, revealed through dissolved Fe distributions, phytoplankton Fe content, and shipboard incubation experiments. Early results from ongoing experiments using a high-resolution coupled physical-biogeochemical model of the ASP give clues as to sources and delivery routes for bioavailable Fe, and suggest that particulate Fe delivered from underneath the bordering ice shelves may also become available to phytoplankton. The ecosystems of both regions are poised in states that may be altered by regional climate change.