Hillary A. Scannell1, Gregory C. Johnson2, LuAnne Thompson1, John M. Lyman2,3, and Steve C. Riser1.
1 School of Oceanography, University of Washington, Seattle, WA, USA.
2 Pacific Marine Environmental Laboratory, NOAA, Seattle, WA, USA.
3 Joint Institute for Marine and Atmospheric Research, University of Hawaii at Manoa, Honolulu, HI, USA
- Return of The Blob, with warming and freshening, hence more buoyancy.
- Summertime heatwaves, increase stratification, inhibit mixing.
- Wintertime mixing, warming penetrates the deep, provides memory.
The reappearance of a northeast Pacific marine heatwave (MHW) sounded alarms in late summer 2019 for a warming event on par with the 2013–2016 MHW known as The Blob. Despite these two events having similar magnitudes in surface warming, differences in seasonality and salinity distinguish their evolutions. We compare and contrast the ocean’s role in the evolution and persistence of the 2013–2016 and 2019–2020 MHWs using mapped temperature and salinity data from Argo floats. An unusual near‐surface freshwater anomaly in the Gulf of Alaska during 2019 increased the stability of the water column, preventing the MHW from penetrating deep as strongly as the 2013–2016 event. This freshwater anomaly likely contributed to the intensification of the MHW by increasing the near‐surface buoyancy. The gradual buildup of subsurface heat content throughout 2020 in the region suggests the potential for persistent ecological impacts.
This article has been accepted for publication in Geophysical Research Letters on November 16, 2020 and has undergone full peer review.
We welcome comments, questions, or feedback via github issues.
The bulk of the analysis for this paper was performed on Microsoft Azure using a Data Science Virtual Machine. The analysis contains a mix of MATLAB and Python code. The Python code leverages xarray and GSW-Python.
The NOAA OISSTv2 dataset was provided by the NOAA/OAR/ESRL PSL, Boulder, Colorado, USA, from their Web site at https://psl.noaa.gov/. Argo data were collected and made freely available by the International Argo Program and the national programs that contribute to it (http://www.argo.ucsd.edu and http://argo.jcommops.org). The Argo Program is part of the Global Ocean Observing System.
This research was supported by NOAA Research and NOAA’s Global Ocean Monitoring and Observing Program. We recieved funding from NOAA (NA15OAR4320063) and the Leonardo DiCaprio Foundation and Microsoft (AI for Earth Innovation Grant).
Cloud resources were provided by Microsfot Azure. Amanda Tan from the eScience Institue at the University of Washington provided technical cloud computing support.