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Winter Sets The Ocean’s Clocks

April 10, 2024

Research fishery biologist Katey Marancik shares how the data she and others collected during the winter 2024 Ecosystem Monitoring Survey are an important starting point for understanding the ocean’s clock for the year.

A large piece of ocean water sampling gear sits on the side deck of a research vessel while at sea. The ocean is choppy and the sunrise is peeking through the clouds. A choppy morning during the winter 2024 Ecosystem Monitoring Survey. Credit: NOAA Fisheries/Katey Marancik

Have you ever forgotten to change your clocks for Daylight Saving Time? You spend the whole day running behind or ahead—trying to catch up. Collecting EcoMon data in the winter on the Northeast continental shelf helps us set our environmental clocks. Without these data, we spend the rest of the year catching up on what has happened just below the ocean’s surface during winter.

Winter Storms Bring Spring Blooms, Too

A large piece of ocean water sampling gear is being deployed over the side of a research vessel while at sea. The sky is bright blue and the seas are calm.
One of the rarely calm winter sampling days. It was so calm, the CTD hung straight on its cable during deployment. Credit: NOAA Fisheries/Katey Marancik

During the relative calm of spring, summer, and fall, the ocean waters stratify into distinct layers. Although some mixing of these layers happens during any storm, winter storms tend to be more intense and more frequent.

Strong winter storms mix up even the deepest layers and deliver nutrients from the bottom to upper layers where they are available to support life. Add sunlight, and you get a spring bloom!

Because of this, the water properties that define the rest of the year are determined in winter.

Winter EcoMon was only 6 days long this year. We had two storms that impacted our sampling, including how we got to the ship. However, the days between storms were some of the calmest winter days at sea I’ve ever seen.

The Season Of Change Is Changing

A large piece of ocean water sampling gear is tied down on the deck of a research vessel while at sea. It is night and the gear is illuminated by the vessel's lights.
Conductivity, Temperature, and Depth (CTD) sampling occurs day and night during the EcoMon Survey. Credit: NOAA Fisheries/Katey Marancik

Winter is the season of drastic change, a datapoint we’ve been missing from direct measurements since 2017.

One of the most important missions of the EcoMon project is to record short-term seasonal and long-term decadal changes in the marine ecosystem. The Northeast continental shelf has a large temperature range between seasons with hot summers and cold winters. Historically, February is the coldest month.

However, this area is also one of the fastest warming regions in the world. That warming doesn’t happen equally among seasons. Faster warming in spring and summer means that the timing of winter could shift by a few days or weeks. That means February may not actually be the coldest month for long, and that could mean changes to patterns the rest of the year.

Tracking Ocean Change

 Blue-gloved hands hold a small vile and forceps near a petri dish placed under a dissecting microscope. The petri dish is filled with lots of nearly microscopic plankton and is illuminated from below.
Looking for pteropods under the microscope during winter 2024 EcoMon survey as part of survey’s ocean acidification work. Credit: NOAA Fisheries/Katey Marancik

Despite it being important to better understand ocean acidification in the winter, it’s under-sampled across our region. The ocean is becoming more acidic as it absorbs more carbon dioxide from the air. Throughout this survey, we took measurements of dissolved inorganic carbon, total alkalinity, and pH to help estimate the rate of ocean acidification. We took these measurements at multiple depths between the surface and the bottom at several locations in the southern New England and Gulf of Maine regions. We also collected small, free-swimming marine snails called pteropods to measure how lower ocean pH is affecting their shells.

We sampled, day and night, to help set our environmental clocks. Measuring the temperature, salinity, nutrients, carbon, and acidity directly from the ocean gives us the most reliable data to estimate patterns throughout the water column, from the surface to the bottom. And, winter data provides us with an important starting point for the coming year.

That’s it for winter EcoMon 2024! This week at sea was an adventure!

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