# Datasets associated with Ishii et al., "New isoprenoid GDGT index as a water mass and temperature proxy in the Southern Ocean"
This repository holds the dataset associated with Ishii et al., "New isoprenoid GDGT index as a water mass and temperature proxy in the Southern Ocean". It contains reanalysed global and Southern Ocean core-top data and late Pleistocene sediment core data used to develop and validate a new isoGDGT-based index for the Antarctic Zone.

## File Overview

### 1. [Ishiietal_SouthernOcean_coretop.xlsx](Ishiietal_SouthernOcean_coretop.xlsx)
Contains Southern Ocean core-top GDGT data (n = 289) from sites south of 35°S, compiled from Tierney and Tingley (2015), Jaeschke et al. (2017), and Lamping et al. (2021). Used for Principal Component Analysis (PCA) and index comparisons.

**Sheets included:**
- Coretop(SO): Core-top dataset with GDGT concentrations and calculated indices
- WOA18_temp: Temperature data from World Ocean Atlas 2018 (0.25° × 0.25° grid)
- WOA18_salinity: Salinity data from World Ocean Atlas 2018 (0.25° × 0.25° grid)
- WOA18_oxygen: Dissolved oxygen data from World Ocean Atlas 2018 (1.0° × 1.0° grid)

**Coretop(SO) variables:**
-	Core name, Source, Latitude, Longitude
-	ACC classification (North, ACC, South)
-	Polar Front classification (SouthPF or NorthPF)
-	GDGT concentrations (GDGT-0, GDGT-1, GDGT-2, GDGT-3, Crenarchaeol, Cren')
-	Calculated indices: MI (methane index), fcren, GDGT-2/3, %GDGT-0, TEX₈₆, TEX₈₆ᴸ, AIZ (this study)
-	Principal components: PC1, PC2

**WOA18 sheets variable:**
-	Core metadata (name, source, location, ACC/PF classification)
-	GDGT concentrations
- Seasonal and annual oceanographic data at multiple depths (0-1400 m):
  - **Parameters**: Temperature (°C), Salinity (unitless), Dissolved oxygen (μmol/kg)
  - **Seasons**: Annual, Spring, Summer, Autumn, Winter
  - **Depths**: 0, 100, 200, 400, 600, 800, 1000, 1200 m

### 2. [Ishiietal_Global_coretop.xlsx](Ishiietal_Global_coretop.xlsx)
Global core-top GDGT dataset (n = 916) compiled from Tierney and Tingley (2015), Jaeschke et al. (2017), and Lamping et al. (2021). Contains similar variables to the Southern Ocean dataset but with global coverage. Used for PCA and index comparisons.

### 3. [Ishiietal_Comparison_160ka.xlsx](Ishiietal_Comparison_160ka.xlsx)
Sediment core isoGDGT records spanning the past 160 kyr from the Southern Ocean, combining new and previously published data.

**New records (IODP Expedition 382):**
-	U1538: 57.43°S, 43.35°W, 3131 m depth (northern Scotia Sea)
-	U1537: 59.11°S, 40.91°W, 3713 m depth (southern Scotia Sea)
  
**Previously published records (Ai et al., 2020; 2024):**
-	MD11-3357: 44.68°S, 80.43°E, 3349 m depth (southeastern Indian Ocean)
-	MD12-3394: 48.38°S, 64.58°E, 2320 m depth (southeastern Indian Ocean)
-	MD11-3353: 50.57°S, 68.39°E, 1568 m depth (southeastern Indian Ocean)
  
**Variables (separate sheet for each core):**
-	Age (ka)
-	GDGT concentrations (GDGT-0, GDGT-1, GDGT-2, GDGT-3, Cren, Cren')
-	Temperature proxies: TEX₈₆, BAYSPAR mean SST, TEX₈₆ᴸ, TEX₈₆ᴸ SST (Kim et al., 2012 calibration)
-	OPTiMAL outputs: D_nearest, SST, StDev (Dunkley Jones et al., 2020)
-	New indices: AIZ and AIZ subST (this study)

### References
>-	Ai, X. E., Studer, A. S., Sigman, D. M., Martínez-García, A., Fripiat, F., Thöle, L. M., Michel, E., Gottschalk, J., Arnold, L., Moretti, S., Schmitt, M., Oleynik, S., Jaccard, S. L., and Haug, G. H.: Southern Ocean upwelling, Earth’s obliquity, and glacial-interglacial atmospheric CO2 change, Science, 370, 1348–1352, https://doi.org/10.1126/science.abd2115, 2020.
>-	Ai, X. E., Thöle, L. M., Auderset, A., Schmitt, M., Moretti, S., Studer, A. S., Michel, E., Wegmann, M., Mazaud, A., Bijl, P. K., Sigman, D. M., Martínez-García, A., and Jaccard, S. L.: The southward migration of the Antarctic Circumpolar Current enhanced oceanic degassing of carbon dioxide during the last two deglaciations, Commun. Earth Environ., 5, 58, https://doi.org/10.1038/s43247-024-01216-x, 2024.  
>-	Boyer, T. P., García, H. E., Locarnini, R. A., Zweng, M. M., Mishonov, A. V., Reagan, J. R., Weathers, K. A., Baranova, O. K., Paver, C. R., Seidov, D., & Smolyar, I. V.: World Ocean Atlas: Temperature, salinity, and oxygen, NOAA National Centers for Environmental Information. [data set]. https://repository.library.noaa.gov/view/noaa/49137, 2018.
>-	Dunkley Jones, T., Eley, Y. L., Thomson, W., Greene, S. E., Mandel, I., Edgar, K., and Bendle, J. A.: OPTiMAL: A new machine learning approach for GDGT-based palaeothermometry, Clim. Past, 16, 2599–2617, https://doi.org/10.5194/CP-16-2599-2020, 2020.
>-	Jaeschke, A., Wengler, M., Hefter, J., Ronge, T. A., Geibert, W., Mollenhauer, G., Gersonde, R., and Lamy, F.: A biomarker perspective on dust, productivity, and sea surface temperature in the Pacific sector of the Southern Ocean, Geochim. Cosmochim. Acta, 204, 120–139, https://doi.org/10.1016/j.gca.2017.01.045, 2017.
>-	Kim, J. H., Crosta, X., Willmott, V., Renssen, H., Bonnin, J., Helmke, P., Schouten, S., and Sinninghe Damsté, J. S.: Holocene subsurface temperature variability in the eastern Antarctic continental margin, Geophys. Res. Lett., 39, L06705, https://doi.org/10.1029/2012GL051157, 2012.
>-	Lamping, N., Müller, J., Hefter, J., Mollenhauer, G., Haas, C., Shi, X., Vorrath, M. E., Lohmann, G., and Hillenbrand, C. D.: Evaluation of lipid biomarkers as proxies for sea ice and ocean temperatures along the Antarctic continental margin, Clim. Past, 17, 2305–2326, https://doi.org/10.5194/cp-17-2305-2021, 2021.
>-	Tierney, J. E. and Tingley, M. P.: A Bayesian, spatially-varying calibration model for the TEX86 proxy, Geochim. Cosmochim. Acta 127, 83–106, https://doi.org/10.1016/j.gca.2013.11.026, 2014.

### Author
Hana Ishii

### License
This dataset is released under Creative Commons Zero v1.0 Universal [CC0-1.0] license.