There is speculation that the state of the ocean may be changing and we may be seeing the emergence of a new dominant mode of climate variability in the Pacific, the North Pacific Mode - look out El Nino, the "Blob" may become the new black.
In addition to the presence of the "Blob" in the North Pacific, we are transitioning into a positive phase of the Interdecadal Pacific Oscillation (IPO), a positive phase of the Pacific Decadal Oscillation (PDO), as well as an El Nino state. The IPO is one of the least well understood climate oscillations as it has a long period of variability (~15-30 years), so it is difficult to observe frequently. It differs from the PDO in that it also influences the SSTs in the South Pacific as well. The last positive phase of the IPO occurred between 1978 and 1999, during which time one of the largest El Nino events was observed in 1997-1998. While the "Blob” currently makes up part of the pattern comprising the transition from positive phase of the PDO and the IPO, the origins of that transition will be a research subject for the scientific community in the coming years. We are excited to be sampling the water column during such a dynamic time.
|P16N leg 1 cruise track between Tahiti and Hawaii mostly following 150 degrees W.|
|SST anomaly for April 28, 2015.|
One of our CTD watchstanders, Annie Foppert has been analyzing that data on board, looking out for anomalously warm waters. So far, we have been in anomalously warm surface waters nearly our entire time around the equator. The plot below shows the raw SST from the underway system during the cruise from 17 deg S through 2 degrees north of the equator. In addition, the climatological SSTs from NOAA are also plotted for reference. A climatology is a long term average over time. It gives us a reference point, or a mean state, for comparison to what is happening now. Most people refer to the climatological state as "normal." So if you wanted to know if the SSTs were warmer than normal - you would reference what you are measuring to the climatology and see if it was warmer or cooler.
The warm anomaly - in that the water is much warmer than the climatology - can be clearly seen by comparing the climatology to the underway temperatures. The underway temperature is indeed warmer than even the three standard deviations of variability around the climatology, for the period of time around the equator - from 2 degrees S until about our present position north of the equator. We are only a few degrees north at the moment, but the SSTs are still climbing.
In addition, we are noticing the developing El Nino conditions along our equatorial transect. The thermocline has deepened -when compared to our prior occupation in 2006. Also, the mixed layer temperatures between 3 degrees S and 3 degrees N are 2.87 deg C warmer than 2006. So the warm water is not isolated to the surface.
The warm waters have made an impression on our P16N scientists and crew in one way or another. One of the night watch scientists pointed out how pleasant it made sampling from the niskins - "The warm water feels nice over my rubber gloves". One of the crew even went so far as to describe it as "hot". The rosette frame for the CTD and bottles was warm to the touch when it came out of the water and back on deck, such that both of the individuals recovering the rosette commented on its warmth upon touching it. Science you can feel - priceless.