Denim and Pool Day

Today was declared denim day (by our newly established science party morale chief) to make everyone look good. The weather has been great, so we also used the new pool (purchased in Hawaii) on the aft deck for the first time. However, as we are constantly heading further north, I suspect that only our die-hard Alaskan participants will be found in the pool in a few days or so.

Denim-wearers gathering in the CTD lab

The pool

Radiocarbon dating of organic material dissolved in seawater: How old is it?

The ocean contains far more than salts and living organisms. The next time you take a swim think about the many thousands of diverse dissolved organic molecules (DOM) you are swimming through. DOM is operationally defined as smaller than a bacterial cell (0.1µm). It includes viruses and large (such as DNA) to very small molecules (amino acids and sugars).  The world's ocean mixes every ~1500 years, however the age of DOM is much older (4-6,000 yrs) suggesting many of these molecules are not efficiently removed by bacteria and persist for multiple ocean mixing cycles. In this way, the large DOM reservoir (662 GtC) stores carbon and mediates Earth's climate on immediate to millennial timescales. 

            

Our group's goal on this cruise is to understand the relative cycling rates of these molecules by determining their radiocarbon (14C) ages . We are particularly interested in determining the sources and cycling of highly-aged DOM components with human-induced inputs, such as combustion products, which we call Black Carbon (BC). We collect filtered seawater from the Niskin bottles at many depths and freeze them on board until we can analyze them back on land at the UC Irvine, Keck Carbon Cycle Accelerator Mass Spectrometer (AMS) Lab.  

Freezer samples on board

Mass Spectrometer back on land

 

  

by Brett Walker

Underway at last

We are finally sailing, leaving Pearl Harbor on Memorial Day 2015. The failure of the compressor of one of the air-cons kept us in port a bit longer than expected. Six days to be exact, some of which will be added at the end of the cruise. By now, we have completed a CTD test cast around the 1000 m isobath as well as a bongo net test cast and are underway to our first real station along 152ºW. The weather is calm, and we are hopeful for a smooth trip (aka "bunny cruise")! 

Last view of Diamond Head Crater and Honolulu, learning about the CTD rosette and mounted instruments, pteropods from the bongo net test cast, and chief scientist (Alison Macdonald) and CTD student (Andrew Shao) working in the TV lounge (taking a break from the very cold computer room, brrr).

Getting ready

The last occupation of the P16N Hawaii-Alaska leg took place in March 2006 on the R/V Thompson. Almost a decade later, we are about to head out into the northeastern Pacific again, this time on the R/V Brown. Leg 1 from Tahiti-Hawaii is already complete. See their blog posts here.

Picture taken from Bridge of R/V Thompson in 2006, somewhere along 152°W.