Lu, Z., Rickaby, R.E.M., Kennedy, H., Kennedy, P., Pancost, R.D., Shaw, S., Lennie, A., Wellner, J. and Anderson, J.B. 2012. An ikaite record of late Holocene climate at the Antarctic Peninsula. Earth and Planetary Science Letters 325-326: 108-115.
The authors write that ikaite "is a low temperature polymorph of calcium carbonate that is hydrated with water molecules contained in its crystal lattice," and they say that "ikaite crystals from marine sediments, if collected and maintained at low temperatures, preserve hydration waters and their intact crystal structures, both of which have the potential to provide isotopic constraints on past climate change," after which they report on what they describe as "the first downcore δ18O record of natural ikaite hydration waters and crystals collected from the Antarctic Peninsula (AP)," which they say were "suitable for reconstructing a low resolution ikaite record of the last 2000 years." This record, as they continue, "qualitatively supports that both the Medieval Warm Period and Little Ice Age extended to the Antarctic Peninsula." They also state that the "most recent crystals suggest a warming relative to the LIA in the last century, possibly as part of the regional recent rapid warming," and they importantly indicate that "this climatic signature is not yet as extreme in nature as the MWP," suggesting that even the dramatic recent warming of the AP may not yet have returned that region to the degree of warmth that was experienced there during the MWP.